Aviation weather report types

A graphic providing conversion tables for the most used weather elements that will be ecountered by pilots. this inludes time, windspeed, speed, temperature, pressure - altitude, and altimeter setting.

  • The AWRP review and decision-making process applies criteria to weather products at various stages . The stages are composed of the following:
    1. Sponsorship of user needs.
    2. R & D and controlled testing.
    3. Experimental application.
    4. Operational application.
  • Pilots and operators should be aware that weather services provided by entities other than FAA, NWS, or their contractors may not meet FAA/NWS quality control standards. Hence, operators and pilots contemplating using such services should request and/or review an appropriate description of services and provider disclosure. This should include, but is not limited to, the type of weather product (for example, current weather or forecast weather), the currency of the product (that is, product issue and valid times), and the relevance of the product. Pilots and operators should be cautious when using unfamiliar products, or products not supported by FAA/NWS technical specifications.

    NOTE- When in doubt, consult with a FAA Flight Service Station Specialist. NOTE- When in doubt, consult with a FAA Flight Service Station Specialist.
    1. Observations. Raw weather data collected by some type of sensor suite including surface and airborne observations, radar, lightning, satellite imagery, and profilers.
    2. Analysis. Enhanced depiction and/or interpretation of observed weather data.
    3. Forecasts. Predictions of the development and/or movement of weather phenomena based on meteorological observations and various mathematical models.

    NOTE- Commercial weather information providers contracted by FAA to provide weather observations, analyses, and forecasts (e.g., contract towers) are included in the Federal Government category of approved sources by virtue of maintaining required technical and quality assurance standards under Federal Government oversight.

    1. The GFA website is intended to provide the necessary aviation weather information to give users a complete picture of the weather that may affect flight in the continental United States (CONUS). The website includes observational data, forecasts, and warnings that can be viewed from 14 hours in the past to 15 hours in the future, including thunderstorms, clouds, flight category, precipitation, icing, turbulence, and wind. Hourly model data and forecasts, including information on clouds, flight category, precipitation, icing, turbulence, wind, and graphical output from the National Weather Service's (NWS) National Digital Forecast Data (NDFD) are available. Wind, icing, and turbulence forecasts are available in 3,000 ft increments from the surface up to 30,000 ft MSL, and in 6,000 ft increments from 30,000 ft MSL to 48,000 ft MSL. Turbulence forecasts are also broken into low (below 18,000 ft MSL) and high (at or above 18,000 ft MSL) graphics. A maximum icing graphic and maximum wind velocity graphic (regardless of altitude) are also available. Built with modern geospatial information tools, users can pan and zoom to focus on areas of greatest interest. Target users are commercial and general aviation pilots, operators, briefers, and dispatchers.
    2. Weather Products.
      1. The Aviation Forecasts include gridded displays of various weather parameters as well as NWS textual weather observations, forecasts, and warnings. Icing, turbulence, and wind gridded products are three-dimensional. Other gridded products are two-dimensional and may represent a “composite” of a three-dimensional weather phenomenon or a surface weather variable, such as horizontal visibility. The following are examples of aviation forecasts depicted on the GFA:
        1. Terminal Aerodrome Forecast (TAF)
        2. Ceiling & Visibility (CIG/VIS)
        3. Clouds
        4. Precipitation / Weather (PCPN/WX)
        5. Thunderstorm (TS)
        6. Winds
        7. Turbulence
        8. Ice
        1. METAR
        2. Precipitation/Weather (PCPN/WX)
        3. Ceiling & Visibility (CIG/VIS)
        4. Pilot Weather Report ( PIREP )
        5. Radar & Satellite (RAD/SAT)

        NOTE- The contiguous United States (U.S.) refers to the 48 adjoining U.S. states on the continent of North America that are south of Canada and north of Mexico, plus the District of Columbia. The term excludes the states of Alaska and Hawaii, and all off-shore U.S. territories and possessions, such as Puerto Rico.

        FIG 7-1-2
        Aviation Surface Forecast

        A graphic from the AWC depicting visibility, weather phenomena, and winds.

        FIG 7-1-3
        Aviation Cloud Forecast

        A graphic from the AWS depicting cloud coverage, bases, and layers.

    Preflight Briefing
      Flight Service is one of the primary sources for obtaining preflight briefings and to file flight plans by phone or the Internet. Flight Service Specialists are qualified and certificated as Pilot Weather Briefers by the FAA. They are not authorized to make original forecasts, but are authorized to translate and interpret available forecasts and reports directly into terms describing the weather conditions which you can expect along your flight route and at your destination. Prior to every flight, pilots should gather all information vital to the nature of the flight. Pilots can receive a regulatory compliant briefing without contacting Flight Service. Pilots are encouraged to use automated resources and review AC 91-92, Pilot's Guide to a Preflight Briefing, for more information. Pilots who prefer to contact Flight Service are encouraged to conduct a self-brief prior to calling. Conducting a self-brief before contacting Flight Service provides familiarity of meteorological and aeronautical conditions applicable to the route of flight and promotes a better understanding of weather information. Three basic types of preflight briefings (Standard, Abbreviated, and Outlook) are available to serve the pilot's specific needs. Pilots should specify to the briefer the type of briefing they want, along with their appropriate background information. This will enable the briefer to tailor the information to the pilot's intended flight. The following paragraphs describe the types of briefings available and the information provided in each briefing.

      REFERENCE- AIM, Para 5-1-1, Preflight Preparation, for items that are required.
      1. Adverse Conditions. Significant meteorological and/or aeronautical information that might influence the pilot to alter or cancel the proposed flight; for example, hazardous weather conditions, airport closures, air traffic delays, etc. Pilots should be especially alert for current or forecast weather that could reduce flight minimums below VFR or IFR conditions. Pilots should also be alert for any reported or forecast icing if the aircraft is not certified for operating in icing conditions. Flying into areas of icing or weather below minimums could have disastrous results.
      2. VFR Flight Not Recommended. When VFR flight is proposed and sky conditions or visibilities are present or forecast, surface or aloft, that, in the briefer's judgment, would make flight under VFR doubtful, the briefer will describe the conditions, describe the affected locations, and use the phrase “VFR flight not recommended.” This recommendation is advisory in nature. The final decision as to whether the flight can be conducted safely rests solely with the pilot. Upon receiving a “VFR flight not recommended” statement, the non-IFR rated pilot will need to make a “go or no go” decision. This decision should be based on weighing the current and forecast weather conditions against the pilot's experience and ratings. The aircraft's equipment, capabilities and limitations should also be considered.

      NOTE- Pilots flying into areas of minimal VFR weather could encounter unforecasted lowering conditions that place the aircraft outside the pilot's ratings and experience level. This could result in spatial disorientation and/or loss of control of the aircraft.

      NOTE- These first 3 elements of a briefing may be combined in any order when the briefer believes it will help to more clearly describe conditions.

        Available NOTAM (D) information pertinent to the proposed flight, including special use airspace (SUA) NOTAM s for restricted areas, aerial refueling, and night vision goggles (NVG).

      NOTE- Other SUA NOTAMs (D), such as military operations area ( MOA ), military training route ( MTR ), and warning area NOTAM s, are considered “upon request” briefing items as indicated in paragraph 7-1-4b10(a).

      1. NOTAM information may be combined with current conditions when the briefer believes it is logical to do so.
      2. Airway NOTAM s, procedural NOTAM s, and NOTAM s that are general in nature and not tied to a specific airport/facility (for example, flight advisories and restrictions, open duration special security instructions, and special flight rules areas) are briefed solely by pilot request. For complete flight information, pilots are urged to review the Domestic Notices and International Notices found in the External Links section of the Federal NOTAM System (FNS) NOTAM Search System and the Chart Supplement in addition to obtaining a briefing.
      1. For the purpose of this paragraph, SUA and related airspace includes the following types of airspace: alert area, military operations area ( MOA ), warning area, and air traffic control assigned airspace ( ATCAA ). MTR data includes the following types of airspace: IFR training routes ( IR ), VFR training routes ( VR ), and slow training routes (SR).
      2. Pilots are encouraged to request updated information from ATC facilities while in flight.

      Automatic Dependent Surveillance-Broadcast ( ADS-B ). Free traffic, weather, and flight information are available on ADS-B In receivers that can receive data over 978 MHz (UAT) broadcasts. These services are available across the nation to aircraft owners who equip with ADS-B In, with further advances coming from airborne and runway traffic awareness. Even search-and-rescue operations benefit from accurate ADS-B tracking.

      Flight Information Services-Broadcast ( FIS-B ). FIS-B is a free service; but is only available to aircraft that can receive data over 978 MHz (UAT). FIS-B automatically transmits a wide range of weather products with national and regional focus to all equipped aircraft. Having current weather and aeronautical information in the cockpit helps pilots plan more safe and efficient flight paths, as well as make strategic decisions during flight to avoid potentially hazardous weather.

      EXAMPLE- Example of a SIGMET :
      BOSR WS 050600
      SIGMET ROMEO 2 VALID UNTIL 051000
      ME NH VT
      FROM CAR TO YSJ TO CON TO MPV TO CAR
      OCNL SEV TURB BLW 080 EXP DUE TO STG NWLY FLOW. CONDS CONTG BYD 1000Z.

      1. Are issued corresponding to the areas described in FIG 7-1-5. and are only for non-convective weather. The U.S. issues a special category of SIGMET s for convective weather called Convective SIGMET s.
      2. Are identified by an alphabetic designator from November through Yankee, excluding Sierra and Tango. Issuance for the same phenomenon will be sequentially numbered, using the original designator until the phenomenon ends. For example, the first issuance in the Chicago (CHI) area (reference FIG 7-1-5) for phenomenon moving from the Salt Lake City (SLC) area will be SIGMET Papa 3, if the previous two issuances, Papa 1 and Papa 2, had been in the SLC area. Note that no two different phenomena across the country can have the same alphabetic designator at the same time.
      3. Use location identifiers (either VORs or airports) to describe the hazardous weather areas.
      4. Are issued when the following phenomena occur or are expected to occur:
        1. Severe icing not associated with thunderstorms.
        2. Severe or extreme turbulence or clear air turbulence ( CAT ) not associated with thunderstorms.
        3. Widespread dust storms or sandstorms lowering surface visibilities to below 3 miles.
        4. Volcanic ash.
        FIG 7-1-4
        Alaska SIGMET and Area Forecast Zones

        A graphic depicting the Alaska SIGMET and Area Forecast Zones.

  • SIGMET s over oceanic regions (New York Oceanic FIR , Oakland Oceanic FIR including Hawaii, Houston Oceanic FIR , Miami Oceanic FIR , San Juan FIR ), points of latitude and longitude are used to describe the hazard area.
    1. SIGMET s over the Oakland Oceanic FIR west of 140 west and south of 30 north (including the Hawaiian Islands) are identified by an alphabetic designator from November through Zulu.
    2. SIGMET s over the Oakland Oceanic FIR east of 140 west and north of 30 north are identified by an alphabetic designator from Alpha through Mike.
    3. SIGMET s over the New York Oceanic FIR , Houston Oceanic FIR , Miami Oceanic FIR , and San Juan FIR are identified by an alphabetic designator from Alpha through Mike.
    4. In addition to SIGMET s issued for the phenomenon for the contiguous U.S., SIGMET s in the oceanic regions are also issued for:
      1. Tornadoes.
      2. Lines of thunderstorms.
      3. Embedded thunderstorms.
      4. Hail greater than or equal to ¾ inch in diameter.
  • Convective SIGMET
    1. Convective SIGMET s are issued in the conterminous U.S. for any of the following:
      1. Severe thunderstorm due to:
        1. Surface winds greater than or equal to 50 knots.
        2. Hail at the surface greater than or equal to 3 /4 inches in diameter.
        3. Tornadoes.
      2. Embedded thunderstorms.
      3. A line of thunderstorms.
      4. Thunderstorms producing precipitation greater than or equal to heavy precipitation affecting 40 percent or more of an area at least 3,000 square miles.
    2. Any convective SIGMET implies severe or greater turbulence, severe icing, and low-level wind shear. A convective SIGMET may be issued for any convective situation that the forecaster feels is hazardous to all categories of aircraft.
    3. Convective SIGMET bulletins are issued for the western (W), central (C), and eastern (E) United States. (Convective SIGMET s are not issued for Alaska or Hawaii.) The areas are separated at 87 and 107 degrees west longitude with sufficient overlap to cover most cases when the phenomenon crosses the boundaries. Bulletins are issued hourly at H+55. Special bulletins are issued at any time as required and updated at H+55. If no criteria meeting convective SIGMET requirements are observed or forecasted, the message “CONVECTIVE SIGMET. NONE” will be issued for each area at H+55. Individual convective SIGMET s for each area (W, C, E) are numbered sequentially from number one each day, beginning at 00Z. A convective SIGMET for a continuing phenomenon will be reissued every hour at H+55 with a new number. The text of the bulletin consists of either an observation and a forecast or just a forecast. The forecast is valid for up to 2 hours.

      EXAMPLE- CONVECTIVE SIGMET 44C
      VALID UNTIL 1455Z
      AR TX OK
      FROM 40NE ADM-40ESE MLC-10W TXK-50WNW LFK-40ENE SJT-40NE ADM
      AREA TS MOV FROM 26025KT. TOPS ABV FL450.
      OUTLOOK VALID 061455-061855
      FROM 60WSW OKC-MLC-40N TXK-40WSW IGB-VUZ-MGM-HRV-60S BTR-40N
      IAH-60SW SJT-40ENE LBB-60WSW OKC
      WST ISSUANCES EXPD. REFER TO MOST RECENT ACUS01 KWNS FROM STORM PREDICTION CENTER FOR SYNOPSIS AND METEOROLOGICAL DETAILS

      FIG 7-1-5
      SIGMET Locations - Contiguous U.S.

      A graphic depicting the SIGMET and AIRMET locations in the conterminous United States.

      FIG 7-1-6
      Hawaii Area Forecast Locations

      A graphic depicitng the forecast locations in the Hawaii area.

  • AIRMET .AIRMET s are a concise description of the occurrence or expected occurrence of specified en route weather phenomena that may affect the safety of aircraft operations, but at intensities lower than those which require the issuance of a SIGMET .
    1. AIRMET s contain details about IFR conditions, extensive mountain obscuration, turbulence, strong surface winds, icing, and freezing levels. Unscheduled updates and corrections are issued as necessary.
    2. AIRMET s:
      1. Are intended to inform all pilots, but especially Visual Flight Rules pilots and operators of sensitive aircraft, of potentially hazardous weather phenomena.
      2. Are issued on a scheduled basis every 6 hours, except every 8 hours in Alaska. Unscheduled updates and corrections are issued as necessary.
      3. Are intended for dissemination to all pilots in the preflight and en route phase of flight to enhance safety. En route AIRMET s are available over flight service frequencies. Over the contiguous U.S., AIRMET s are also available on equipment intended to display weather and other non-air traffic control-related flight information to pilots using the Flight Information Service-Broadcast ( FIS-B ). In Alaska and Hawaii, AIRMET s are broadcast on air traffic frequencies.
      4. Are issued for the contiguous U.S., Alaska, and Hawaii. No AIRMET s are issued for U.S. Oceanic FIR s in the Gulf of Mexico, Caribbean, Western Atlantic, and Pacific Oceans.

        TBL 7-1-2
        U. S. AIRMET Issuance Time and Frequency
        Product Type Issuance Time Issuance Frequency
        AIRMETs over the Contiguous U.S. 0245, 0845, 1445, 2045 UTC Every 6 hours
        AIRMETs over Alaska 0515, 1315, 2115 UTC
        (standard time) 0415, 1215, 2015 UTC
        (Daylight savings time)        		 Every 8 hours
        AIRMETs over Hawaii 0400, 1000, 1600, 2200 UTC Every 6 hours
        FIG 7-1-7
        AIRMET over the Contiguous U.S.

        A graphic depicting AIRMET over the Contiguous U.S.

      5. AIRMET s over Alaska and Hawaii:
        1. AIRMET s over Alaska and Hawaii are in text format. The hazard areas are described using well-known geographical areas. AIRMET s over Alaska are issued for three Alaskan regions corresponding to Alaska area forecasts (See FIG 7-1-4).
        2. AIRMET s over Alaska are valid up to eight hours. AIRMET s over Hawaii are valid up to six hours. Unscheduled issuances contain an update number for easier identification.
        3. AIRMET Zulu describes moderate icing and provides freezing level heights.

        EXAMPLE- Example of AIRMET Sierra issued for the Southeast Alaska area: WA AK47 PAWU 241324 WA 7O JNUS WA 241315 AIRMET SIERRA FOR IFR AND MT OBSC VALID UNTIL 242115 LYNN CANAL AND GLACIER BAY JB MTS OBSC BY CLDS/ISOL PCPN. NC. CNTRL SE AK JC MTS OCNL OBSC IN CLDS. NC. SRN SE AK JD PAWG-PAKT LN W OCNL CIGS BLW 010/VIS BLW 3SM BR. IMPR. ERN GLF CST JE OCNL CIGS BLW 010/VIS BLW 3SM BR/-RA BR. DTRT. =JNUT WA 241315 AIRMET TANGO FOR TURB/STG SFC WINDS VALID UNTIL 242115 ERN GLF CST JE OFSHR ICY BAY W SUSTAINED SFC WND 30 KTS OR GTR. SPRDG E. INTSF. =JNUZ WA 241315 AIRMET ZULU FOR ICING VALID UNTIL 242115 ERN GLF CST JE 16Z TO 19Z ALG CST W ICY BAY OCNL MOD ICEIC 080-160. FZLVL 045 EXC 015 INLAND. WKN.

        EXAMPLE- Example of AIRMET Tango issued for Hawaii FA area: WA HW31 PHFO 241529 WA 0HI HNLS WA 241600 AIRMET SIERRA UPDATE 2 FOR IFR VALID UNTIL 242200 NO SIGNIFICANT IFR EXP. =HNLT WA 241600 AIRMET TANGO UPDATE 3 FOR TURB VALID UNTIL 242200 AIRMET TURB. HI OVER AMD IMT S THRU W OF MTN. TEMPO MOD TURB BLW 070. COND CONT BEYOND 2200Z. =HNLZ WA 241600 AIRMET ZULU UPDATE 2 FOR ICE AND FZLVL VALID UNTIL 242200 NO SIGNIFICANT ICE EXP

        EXAMPLE- Example of an Aviation Watch Notification Message:
        WWUS30 KWNS 271559
        SAW2
        SPC AWW 271559
        WW 568 TORNADO AR LA MS 271605Z - 280000Z
        AXIS..65 STATUTE MILES EAST AND WEST OF LINE..
        45ESE HEZ/NATCHEZ MS/ - 50N TUP/TUPELO MS/
        ..AVIATION COORDS.. 55NM E/W /18WNW MCB - 60E MEM/
        HAIL SURFACE AND ALOFT..3 INCHES. WIND GUSTS..70 KNOTS. MAX TOPS TO 550. MEAN STORM MOTION VECTOR 26030.
        LAT. LON 31369169 34998991 34998762 31368948
        THIS IS AN APPROXIMATION TO THE WATCH AREA. FOR A COMPLETE DEPICTION OF THE WATCH SEE WOUS64 KWNS FOR WOU2.

        EXAMPLE- Example of a Public Tornado Watch Notification Message:
        WWUS20 KWNS 050550
        SEL2
        SPC WW 051750
        URGENT - IMMEDIATE BROADCAST REQUESTED
        TORNADO WATCH NUMBER 243
        NWS STORM PREDICTION CENTER NORMAN OK
        1250 AM CDT MON MAY 5 2011
        THE NWS STORM PREDICTION CENTER HAS ISSUED A
        *TORNADO WATCH FOR PORTIONS OF
        WESTERN AND CENTRAL ARKANSAS
        SOUTHERN MISSOURI
        FAR EASTERN OKLAHOMA
        *EFFECTIVE THIS MONDAY MORNING FROM 1250 AM UNTIL 600 AM CDT.
        . THIS IS A PARTICULARLY DANGEROUS SITUATION.
        *PRIMARY THREATS INCLUDE
        NUMEROUS INTENSE TORNADOES LIKELY
        NUMEROUS SIGNIFICANT DAMAGING WIND GUSTS TO 80 MPH LIKELY
        NUMEROUS VERY LARGE HAIL TO 4 INCHES IN DIAMETER LIKELY
        THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 100 STATUTE MILES EAST AND WEST OF A LINE FROM 15 MILES WEST NORTHWEST OF FORT LEONARD WOOD MISSOURI TO 45 MILES SOUTHWEST OF HOT SPRINGS ARKANSAS. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU2).
        REMEMBER. A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE WARNINGS.
        OTHER WATCH INFORMATION. THIS TORNADO WATCH REPLACES TORNADO WATCH NUMBER 237. WATCH NUMBER 237 WILL NOT BE IN EFFECT AFTER
        1250 AM CDT. CONTINUE. WW 239. WW 240. WW 241. WW 242.
        DISCUSSION. SRN MO SQUALL LINE EXPECTED TO CONTINUE EWD. WHERE LONG/HOOKED HODOGRAPHS SUGGEST THREAT FOR EMBEDDED SUPERCELLS/POSSIBLE TORNADOES. FARTHER S. MORE WIDELY SCATTERED
        SUPERCELLS WITH A THREAT FOR TORNADOES WILL PERSIST IN VERY STRONGLY DEEP SHEARED/LCL ENVIRONMENT IN AR.
        AVIATION. TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION VECTOR 26045.

        1. CWA s are unscheduled inflight, flow control, air traffic, and air crew advisory. By nature of its short lead time, the CWA is not a flight planning product. It is generally a nowcast for conditions beginning within the next two hours. CWA s will be issued:
          1. As a supplement to an existing SIGMET , Convective SIGMET or AIRMET .
          2. When an Inflight Advisory has not been issued but observed or expected weather conditions meet SIGMET / AIRMET criteria based on current pilot reports and reinforced by other sources of information about existing meteorological conditions.
          3. When observed or developing weather conditions do not meet SIGMET , Convective SIGMET , or AIRMET criteria; e.g., in terms of intensity or area coverage, but current pilot reports or other weather information sources indicate that existing or anticipated meteorological phenomena will adversely affect the safe flow of air traffic within the ARTCC area of responsibility.

          EXAMPLE- ZKC3 CWA 032140
          ZKC CWA 301 VALID UNTIL 032340
          ISOLD SVR TSTM over KCOU MOVG SWWD 10 KTS ETC.

          1. Categorical outlook terms, describing general ceiling and visibility conditions for advanced planning purposes are used only in area forecasts and are defined as follows:
            1. LIFR (Low IFR). Ceiling less than 500 feet and/or visibility less than 1 mile.
            2. IFR. Ceiling 500 to less than 1,000 feet and/or visibility 1 to less than 3 miles.
            3. MVFR (Marginal VFR). Ceiling 1,000 to 3,000 feet and/or visibility 3 to 5 miles inclusive.
            4. VFR. Ceiling greater than 3,000 feet and visibility greater than 5 miles; includes sky clear.
            1. LIFR CIG-low IFR due to low ceiling.
            2. IFR FG-IFR due to visibility restricted by fog.
            3. MVFR CIG HZ FU-marginal VFR due to both ceiling and visibility restricted by haze and smoke.
            4. IFR CIG RA WIND-IFR due to both low ceiling and visibility restricted by rain; wind expected to be 25 knots or greater.
            1. Attention all aircraft, SIGMET Delta Three, from Myton to Tuba City to Milford, severe turbulence and severe clear icing below one zero thousand feet. Expected to continue beyond zero three zero zero zulu.
            2. Attention all aircraft, convective SIGMET Two Seven Eastern. From the vicinity of Elmira to Phillipsburg. Scattered embedded thunderstorms moving east at one zero knots. A few intense level five cells, maximum tops four five zero.
            3. Attention all aircraft, Kansas City Center weather advisory one zero three. Numerous reports of moderate to severe icing from eight to niner thousand feet in a three zero mile radius of St. Louis. Light or negative icing reported from four thousand to one two thousand feet remainder of Kansas City Center area.

            Terminal control facilities have the option to limit hazardous weather information broadcast as follows: Tower cab and approach control positions may opt to broadcast hazardous weather information alerts only when any part of the area described is within 50 miles of the airspace under their jurisdiction.

            REFERENCE-

            FAA Order JO 7110.65, Para 2-6-6, Hazardous Inflight Weather Advisory.

            1. Data link Service Providers ( DSP s). DSP s deploy and maintain airborne, ground-based, and, in some cases, space-based infrastructure that supports the transmission of AI/MET information over one or more physical links. A DSP may provide a free of charge or a for-fee service that permits end users to uplink and downlink AI/MET and other information. The following are examples of DSP s:
              1. FAA FIS-B. A ground-based broadcast service provided through the ADS-B Universal Access Transceiver (UAT) network. The service provides users with a 978 MHz data link capability when operating within range and line-of-sight of a transmitting ground station. FIS-B enables users of properly equipped aircraft to receive and display a suite of broadcast weather and aeronautical information products.
              2. Non-FAA FIS Systems. Several commercial vendors provide customers with FIS data over both the aeronautical spectrum and on other frequencies using a variety of data link protocols. Services available from these providers vary greatly and may include tier based subscriptions. Advancements in bandwidth technology permits preflight as well as inflight access to the same MET and AI information available on the ground. Pilots and operators using non-FAA FIS for MET and AI information should be knowledgeable regarding the weather services being provided as some commercial vendors may be repackaging NWS sourced weather, while other commercial vendors may alter the weather information to produce vendor-tailored or vendor-specific weather reports and forecasts.
              1. Broadcast Mode: A one-way interaction in which AI and/or MET updates or changes applicable to a designated geographic area are continuously transmitted (or transmitted at repeated periodic intervals) to all aircraft capable of receiving the broadcast within the service volume defined by the system network architecture.
              2. Contract/Demand Mode: A two-way interaction in which AI and/or MET information is transmitted to an aircraft in response to a specific request.
              3. Contract/Update Mode: A two-way interaction that is an extension of the Demand Mode. Initial AI and/or MET report(s) are sent to an aircraft and subsequent updates or changes to the AI and/or MET information that meet the contract criteria are automatically or manually sent to an aircraft.
              1. Before using FIS for inflight operations, pilots and other flight crewmembers should become familiar with the operation of the FIS system to be used, the airborne equipment to be used, including its system architecture, airborne system components, coverage service volume and other limitations of the particular system, modes of operation and indications of various system failures. Users should also be familiar with the specific content and format of the services available from the FIS provider(s). Sources of information that may provide this specific guidance include manufacturer's manuals, training programs, and reference guides.
              2. FIS should not serve as the sole source of aviation weather and other operational information. ATC, FSSs, and, if applicable, AOCC VHF/ HF voice remain as a redundant method of communicating aviation weather, NOTAM s, and other operational information to aircraft in flight. FIS augments these traditional ATC/ FSS /AOCC services and, for some products, offers the advantage of being displayed as graphical information. By using FIS for orientation, the usefulness of information received from conventional means may be enhanced. For example, FIS may alert the pilot to specific areas of concern that will more accurately focus requests made to FSS or AOCC for inflight updates or similar queries made to ATC.
              3. The airspace and aeronautical environment is constantly changing. These changes occur quickly and without warning. Critical operational decisions should be based on use of the most current and appropriate data available. When differences exist between FIS and information obtained by voice communication with ATC, FSS, and/or AOCC (if applicable), pilots are cautioned to use the most recent data from the most authoritative source.
              4. FIS aviation weather products (for example, graphical ground-based radar precipitation depictions) are not appropriate for tactical (typical timeframe of less than 3 minutes) avoidance of severe weather such as negotiating a path through a weather hazard area. FIS supports strategic (typical timeframe of 20 minutes or more) weather decision-making such as route selection to avoid a weather hazard area in its entirety. The misuse of information beyond its applicability may place the pilot and aircraft in jeopardy. In addition, FIS should never be used in lieu of an individual preflight weather and flight planning briefing.
              5. DSP s offer numerous MET and AI products with information that can be layered on top of each other. Pilots need to be aware that too much information can have a negative effect on their cognitive work load. Pilots need to manage the amount of information to a level that offers the most pertinent information to that specific flight without creating a cockpit distraction. Pilots may need to adjust the amount of information based on numerous factors including, but not limited to, the phase of flight, single pilot operation, autopilot availability, class of airspace, and the weather conditions encountered.
              6. FIS NOTAM products, including Temporary Flight Restriction (TFR) information, are advisory-use information and are intended for situational awareness purposes only. Cockpit displays of this information are not appropriate for tactical navigation - pilots should stay clear of any geographic area displayed as a TFR NOTAM. Pilots should contact FSS s and/or ATC while en route to obtain updated information and to verify the cockpit display of NOTAM information.
              7. FIS supports better pilot decision-making by increasing situational awareness. Better decision-making is based on using information from a variety of sources. In addition to FIS, pilots should take advantage of other weather/ NAS status sources, including, briefings from Flight Service Stations, data from other air traffic control facilities, airline operation control centers, pilot reports, as well as their own observations.

              NOTE- The NOTAM -D and NOTAM -FDC products broadcast via FIS-B are limited to those issued or effective within the past 30 days. Except for TFRs, NOTAMs older than 30 days are not provided. The pilot in command is responsible for reviewing all necessary information prior to flight.

              1. Condition observed;
              2. Date and time of observation;
              3. Altitude and location of observation;
              4. Type and call sign of the aircraft; and
              5. Type and software version of avionics system.
              TBL 7-1-3
              FIS-B Over UAT Product Update and Transmission Intervals
              Product Update Interval 1 Transmission Interval (95%) 2 Basic Product
              AIRMET As Available 5 minutes Yes
              AWW/WW As Available, then at 15 minute intervals for 1 hour 5 minutes No
              Ceiling As Available 10 minutes No
              Convective SIGMET As Available, then at 15 minute intervals for 1 hour 5 minutes Yes
              D-ATIS As Available 1 minute No
              Echo Top 5 minutes 5 minutes No
              METAR/SPECI 1 minute (where available), As Available otherwise 5 minutes Yes
              MRMS NEXRAD (CONUS) 2 minutes 15 minutes Yes
              MRMS NEXRAD (Regional) 2 minutes 2.5 minutes Yes
              NOTAMs-D/FDC As Available 10 minutes Yes
              NOTAMs-TFR As Available 10 minutes Yes
              PIREP As Available 10 minutes Yes
              SIGMET As Available, then at 15 minute intervals for 1 hour 5 minutes Yes
              SUA Status As Available 10 minutes Yes
              TAF/AMEND 6 Hours (±15 minutes) 10 minutes Yes
              Temperature Aloft 12 Hours (±15 minutes) 10 minutes Yes
              TWIP As Available 1 minute No
              Winds aloft 12 Hours (±15 minutes) 10 minutes Yes
              Lightning strikes 3 5 minutes 5 minutes Yes
              Turbulence 3 1 minute 15 minutes Yes
              Icing, Forecast Potential (FIP) 3 60 minutes 15 minutes Yes
              Cloud tops 3 30 minutes 15 minutes Yes
              1 Minute AWOS 3 1 minute 10 minutes No
              Graphical-AIRMET 3 As Available 5 minutes Yes
              Center Weather Advisory (CWA) 3 As Available 10 minutes Yes
              Temporary Restricted Areas (TRA) As Available 10 minutes Yes
              Temporary Military Operations Areas (TMOA) As Available 10 minutes Yes

              1 The Update Interval is the rate at which the product data is available from the source. 2 The Transmission Interval is the amount of time within which a new or updated product transmission must be completed (95%) and the rate or repetition interval at which the product is rebroadcast (95%). 3 The transmission and update intervals for the expanded set of basic meteorological products may be adjusted based on FAA and vendor agreement on the final product formats and performance requirements.

              1. Details concerning the content, format, and symbols of the various data link products provided should be obtained from the specific avionics manufacturer.
              2. NOTAM-D and NOTAM-FDC products broadcast via FIS-B are limited to those issued or effective within the past 30 days.

              TBL 7-1-4
              Product Parameters for Low/Medium/High Altitude Tier Radios

              Product

              Surface Radios

              Low Altitude Tier

              Medium Altitude Tier

              High Altitude Tier

              CONUS NEXRAD not provided

              CONUS NEXRAD imagery

              CONUS NEXRAD imagery

              Winds & Temps Aloft

              500 NM look-ahead range

              500 NM look-ahead range

              750 NM look-ahead range

              1,000 NM look-ahead range

              100 NM look-ahead range

              250 NM look-ahead range

              375 NM look-ahead range

              CONUS: CONUS Class B & C airport METARs and 500 NM look-ahead range

              Outside of CONUS: 500 NM look-ahead
              range

              100 NM look-ahead range

              250 NM look-ahead range

              375 NM look-ahead range

              CONUS: CONUS Class B & C airport TAFs and 500 NM look-ahead range

              Outside of CONUS: 500 NM look-ahead
              range

              AIRMET, SIGMET, PIREP, and SUA/SAA

              100 NM look-ahead range. PIREP/SUA/SAA is N/A.

              250 NM look-ahead range

              375 NM look-ahead range

              500 NM look-ahead range

              150 NM look-ahead range

              150 NM look-ahead range

              200 NM look-ahead range

              250 NM look-ahead range

              NOTAMs D, FDC, and TFR

              100 NM look-ahead range

              100 NM look-ahead range

              100 NM look-ahead range

              100 NM look-ahead range

              NOTE- When the barometric pressure exceeds 31.00 inches Hg., see AIM, Para 7-2-3, Altimeter Errors.
                AWOS-A only reports altimeter setting;
              NOTE- Any other information is advisory only. NOTE- Any other information is advisory only.

              EXAMPLE- “Bremerton National Airport automated weather observation, one four five six zulu;”
              “Ravenswood Jackson County Airport automated weather observation, one four five six zulu.”

              EXAMPLE- “Sault Ste. Marie, Chippewa County International Airport automated weather observation;”
              “Sandusky, Cowley Field automated weather observation.”

              EXAMPLE- “Bremerton National Airport automated weather observation test, one four five six zulu.” EXAMPLE- “Bremerton National Airport automated weather observing system temporarily inoperative.”
              1. The lowest reportable visibility value in AWOS is “less than 1 /4.” It is announced as “VISIBILITY LESS THAN ONE QUARTER.”
              2. A sensor for determining visibility is not included in some AWOS. In these systems, visibility is not announced. “VISIBILITY MISSING” is announced only if the system is configured with a visibility sensor and visibility information is not available.

              EXAMPLE- “Bremerton National Airport automated weather observation, one four five six zulu. Ceiling two thousand overcast;” “Bremerton National Airport automated weather observation, one four five six zulu. Indefinite ceiling two hundred, sky obscured.”

              EXAMPLE- “No clouds below one two thousand.”
              “Clear below one two thousand.”
              1. Automated “Remarks.”
                1. Density Altitude.
                2. Variable Visibility.
                3. Variable Wind Direction.

                EXAMPLE- “Remarks . density altitude, two thousand five hundred . visibility variable between one and two . wind direction variable between two four zero and three one zero . observed weather . thunderstorm moderate rain showers and fog . thunderstorm overhead.”

                EXAMPLE- “Ceiling one thousand overcast . visibility three . precipitation . temperature three zero, dew point missing . wind calm . altimeter three zero zero one.”

                1. Automated “REMARKS.”
                  1. Density Altitude.
                  2. Variable Visibility.
                  3. Variable Wind Direction.

                  EXAMPLE- “Remarks . density altitude, two thousand five hundred . visibility variable between one and two . wind direction variable between two four zero and three one zero . observer ceiling estimated two thousand broken . observer temperature two, dew point minus five.”

                  1. System Description.
                    1. The ASOS/AWOS at each airport location consists of these main components:
                      1. Individual weather sensors.
                      2. Data collection and processing units.
                      3. Peripherals and displays.
                      1. Cloud height indicator (one or possibly three).
                      2. Visibility sensor (one or possibly three).
                      3. Precipitation identification sensor.
                      4. Freezing rain sensor (at select sites).
                      5. Pressure sensors (two sensors at small airports; three sensors at large airports).
                      6. Ambient temperature/Dew point temperature sensor.
                      7. Anemometer (wind direction and speed sensor).
                      8. Rainfall accumulation sensor.
                      9. Automated Lightning Detection and Reporting System (ALDARS) (excluding Alaska and Pacific Island sites).

                      NOTE- Wind direction is reported relative to magnetic north in ATIS as well as ASOS and AWOS radio (voice) broadcasts.

                      NOTE- To decode an ASOS/AWOS report, refer to FIG 7-1-8 and FIG 7-1-9.

                      REFERENCE- A complete explanation of METAR terminology is located in AIM, Para 7-1-28, Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR).

                      FIG 7-1-8
                      Key to Decode an ASOS/AWOS (METAR) Observation (Front)

                      A graphic depicting the front side of the key to decode an ASOS/AWSS (METAR) Observation.

                      FIG 7-1-9
                      Key to Decode an ASOS/AWOS (METAR) Observation (Back)

                      A graphic depicting the back side of the key to decode an ASOS/AWSS (METAR) Observation.

                  2. TBL 7-1-5 contains a comparison of weather observing programs and the elements reported.
                  3. Service Standards. During 1995, a government/industry team worked to comprehensively reassess the requirements for surface observations at the nation's airports. That work resulted in agreement on a set of service standards, and the FAA and NWS ASOS sites to which the standards would apply. The term “Service Standards” refers to the level of detail in weather observation. The service standards consist of four different levels of service (A, B, C, and D) as described below. Specific observational elements included in each service level are listed in TBL 7-1-6.
                    1. Service Level D defines the minimum acceptable level of service. It is a completely automated service in which the ASOS/AWOS observation will constitute the entire observation, i.e., no additional weather information is added by a human observer. This service is referred to as a stand alone D site.
                    2. Service Level C is a service in which the human observer, usually an air traffic controller, augments or adds information to the automated observation. Service Level C also includes backup of ASOS/AWOS elements in the event of an ASOS/AWOS malfunction or an unrepresentative ASOS/AWOS report. In backup, the human observer inserts the correct or missing value for the automated ASOS/AWOS elements. This service is provided by air traffic controllers under the Limited Aviation Weather Reporting Station (LAWRS) process, FSS and NWS observers, and, at selected sites, Non-Federal Observation Program observers.
                      Two categories of airports require detail beyond Service Level C in order to enhance air traffic control efficiency and increase system capacity. Services at these airports are typically provided by contract weather observers, NWS observers, and, at some locations, FSS observers.
                    3. Service Level B is a service in which weather observations consist of all elements provided under Service Level C, plus augmentation of additional data beyond the capability of the ASOS/AWOS. This category of airports includes smaller hubs or special airports in other ways that have worse than average bad weather operations for thunderstorms and/or freezing/frozen precipitation, and/or that are remote airports.
                    4. Service Level A, the highest and most demanding category, includes all the data reported in Service Standard B, plus additional requirements as specified. Service Level A covers major aviation hubs and/or high volume traffic airports with average or worse weather.

                      TBL 7-1-5
                      Weather Observing Programs
                      Type
                      ASOS X X X X X X X X X X
                      AWOS-A X
                      AWOS-A/V X X
                      AWOS-1 X X X X
                      AWOS-2 X X X X X
                      AWOS-3 X X X X X X
                      AWOS-3P X X X X X X X
                      AWOS-3T X X X X X X X
                      AWOS-3P/T X X X X X X X X
                      AWOS-4 X X X X X X X X X X X X
                      Manual X X X X X X X
                      REFERENCE- FAA Order JO 7900.5, Surface Weather Observing, for element reporting.
                      TBL 7-1-6
                      SERVICE LEVEL A
                      Service Level A consists of all the elements of Service Levels B, C and D plus the elements listed to the right, if observed. 10 minute longline RVR at precedented sites or
                      additional visibility increments of 1/8, 1/16 and 0 Sector visibility
                      Variable sky condition
                      Cloud layers above 12,000 feet and cloud types
                      Widespread dust, sand and other obscurations
                      Volcanic eruptions
                      SERVICE LEVEL B
                      Service Level B consists of all the elements of Service Levels C and D plus the elements listed to the right, if observed. Longline RVR at precedented sites
                      (may be instantaneous readout)
                      Freezing drizzle versus freezing rain
                      Ice pellets
                      Snow depth & snow increasing rapidly remarks
                      Thunderstorm and lightning location remarks
                      Observed significant weather not at the station
                      remarks
                      SERVICE LEVEL C
                      Service Level C consists of all the elements of Service Level D plus augmentation and backup by a human observer or an air traffic control specialist on location nearby. Backup consists of inserting the correct value if the system malfunctions or is unrepresentative. Augmentation consists of adding the elements listed to the right, if observed. During hours that the observing facility is closed, the site reverts to Service Level D. Thunderstorms
                      Tornadoes
                      Hail
                      Virga
                      Volcanic ash
                      Tower visibility
                      Operationally significant remarks as deemed
                      appropriate by the observer
                      SERVICE LEVEL D
                      This level of service consists of an ASOS or AWOS continually measuring the atmosphere at a point near the runway. The ASOS or AWOS senses and measures the weather parameters listed to the right. Wind
                      Visibility
                      Precipitation/Obstruction to vision
                      Cloud height
                      Sky cover
                      Temperature
                      Dew point
                      Altimeter
                      FIG 7-1-10
                      NEXRAD Coverage

                      A graphic depicting the NEXRAD Coverage in the conterminous United States.

                      FIG 7-1-11
                      NEXRAD Coverage

                      A graphic depicting the NEXRAD coverage in Alaska as of August 20, 1996.

                      FIG 7-1-12
                      NEXRAD Coverage

                      A graphic depicting the NEXRAD coverage in Hawaii and Puerto Rico as of August 20, 1996.

                    5. All En Route Flight Advisory Service facilities and FSS s have equipment to directly access the radar displays from the individual weather radar sites. Specialists at these locations are trained to interpret the display for pilot briefing and inflight advisory services. The Center Weather Service Units located in ARTCC s also have access to weather radar displays and provide support to all air traffic facilities within their center's area.
                    6. For more detailed information on PIREPS, users can refer to the current version of the Aviation Weather Handbook, FAA-H-8083-28.

                      REFERENCE- P/CG Term - PRECIPITATION RADAR WEATHER DESCRIPTIONS.
                      AIM, Para 7-1-26, Thunderstorms.
                      Chart Supplement, Charts, NWS Upper Air Observing Stations and Weather Network for the location of specific radar sites.

                      NOTE- En route ATC radar's Weather and Radar Processor (WARP) does not display light precipitation intensity.

                      1. It is often necessary for ATC to restrict the amount of lateral deviation (“twenty degrees right,” “up to fifteen degrees left,” “up to ten degrees left or right of course”).
                      2. The term “when able, proceed direct,” in an ATC weather deviation clearance, refers to the pilot's ability to remain clear of the weather when returning to course/route.
                      1. Proposed point where detour will commence.
                      2. Proposed route and extent of detour (direction and distance).
                      3. Point where original route will be resumed.
                      4. Flight conditions (IFR or VFR).
                      5. Any further deviation that may become necessary as the flight progresses.
                      6. Advise if the aircraft is equipped with functioning airborne radar.
                      1. RVR values are measured by transmissometers mounted on 14-foot towers along the runway. A full RVR system consists of:
                        1. Transmissometer projector and related items.
                        2. Transmissometer receiver (detector) and related items.
                        3. Analog recorder.
                        4. Signal data converter and related items.
                        5. Remote digital or remote display programmer.
                        TBL 7-1-7
                        Approach Category/Minimum RVR Table
                        Category Visibility (RVR)
                        Nonprecision 2,400 feet
                        Category I 1,800 feet*
                        Category II 1,000 feet
                        Category IIIa 700 feet
                        Category IIIb 150 feet
                        Category IIIc 0 feet
                        1. Forward scatter meter with a transmitter, receiver and associated items.
                        2. A runway light intensity monitor (RLIM).
                        3. An ambient light sensor (ALS).
                        4. A data processor unit (DPU).
                        5. Controller display (CD).
                        1. 100-feet increments for products below 800 feet.
                        2. 200-feet increments for products between 800 feet and 3,000 feet.
                        3. 500-feet increments for products between 3,000 feet and 6,500 feet.
                        4. 25-meter increments for products below 150 meters.
                        5. 50-meter increments for products between 150 meters and 800 meters.
                        6. 100-meter increments for products between 800 meters and 1,200 meters.
                        7. 200-meter increments for products between 1,200 meters and 2,000 meters.

                        REFERENCE- AIM, Para 7-1-28, Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR), defines “broken,” “overcast,” and “obscuration.”

                        1. Surface (horizontal) visibility is reported in METAR reports in terms of statute miles and increments thereof; e.g., 1 /16, 1 /8, 3/ 16, 1 /4, 5/ 16, 3/ 8, 1/ 2, 5/ 8, 3 /4, 7 /8, 1, 1 1 /8, etc. (Visibility reported by an unaugmented automated site is reported differently than in a manual report, i.e., ASOS/AWOS: 0, 1 /16, 1/ 8, 1 /4, 1/ 2, 3 /4, 1, 1 1 /4, 1 1/ 2, 1 3/ 4, 2, 2 1/ 2, 3, 4, 5, etc., AWOS: M 1 /4, 1 /4, 1/ 2, 3 /4, 1, 1 1 /4, 1 1/ 2, 1 3/ 4, 2, 2 1/ 2, 3, 4, 5, etc.) Visibility is determined through the ability to see and identify preselected and prominent objects at a known distance from the usual point of observation. Visibilities which are determined to be less than 7 miles, identify the obscuring atmospheric condition; e.g., fog, haze, smoke, etc., or combinations thereof.
                        2. Prevailing visibility is the greatest visibility equaled or exceeded throughout at least one half of the horizon circle, not necessarily contiguous. Segments of the horizon circle which may have a significantly different visibility may be reported in the remarks section of the weather report; i.e., the southeastern quadrant of the horizon circle may be determined to be 2 miles in mist while the remaining quadrants are determined to be 3 miles in mist.
                        3. When the prevailing visibility at the usual point of observation, or at the tower level, is less than 4 miles, certificated tower personnel will take visibility observations in addition to those taken at the usual point of observation. The lower of these two values will be used as the prevailing visibility for aircraft operations.
                        1. Rain
                          1. Light. From scattered drops that, regardless of duration, do not completely wet an exposed surface up to a condition where individual drops are easily seen.
                          2. Moderate. Individual drops are not clearly identifiable; spray is observable just above pavements and other hard surfaces.
                          3. Heavy. Rain seemingly falls in sheets; individual drops are not identifiable; heavy spray to height of several inches is observed over hard surfaces.
                          1. Light. Scattered pellets that do not completely cover an exposed surface regardless of duration. Visibility is not affected.
                          2. Moderate. Slow accumulation on ground. Visibility reduced by ice pellets to less than 7 statute miles.
                          3. Heavy. Rapid accumulation on ground. Visibility reduced by ice pellets to less than 3 statute miles.
                          1. Light. Visibility more than 1 /2 statute mile.
                          2. Moderate. Visibility from more than 1 /4 statute mile to 1 /2 statute mile.
                          3. Heavy. Visibility 1 /4 statute mile or less.
                          1. FAA air traffic facilities are required to solicit PIREP s when the following conditions are reported or forecast: ceilings at or below 5,000 feet; visibility at or below 5 miles (surface or aloft); thunderstorms and related phenomena; icing of light degree or greater; turbulence of moderate degree or greater; wind shear and reported or forecast volcanic ash clouds.
                          2. Pilots are urged to cooperate and promptly volunteer reports of these conditions and other atmospheric data such as: cloud bases, tops and layers; flight visibility; precipitation; visibility restrictions such as haze, smoke and dust; wind at altitude; and temperature aloft.
                          3. PIREP s should be given to the ground facility with which communications are established; i.e., FSS , ARTCC , or terminal ATC. One of the primary duties of the Inflight position is to serve as a collection point for the exchange of PIREP s with en route aircraft.
                          4. If pilots are not able to make PIREP s by radio, reporting upon landing of the inflight conditions encountered to the nearest FSS or Weather Forecast Office will be helpful. Some of the uses made of the reports are:
                            1. The ATCT uses the reports to expedite the flow of air traffic in the vicinity of the field and for hazardous weather avoidance procedures.
                            2. The FSS uses the reports to brief other pilots, to provide inflight advisories, and weather avoidance information to en route aircraft.
                            3. The ARTCC uses the reports to expedite the flow of en route traffic, to determine most favorable altitudes, and to issue hazardous weather information within the center's area.
                            4. The NWS uses the reports to verify or amend conditions contained in aviation forecast and advisories. In some cases, pilot reports of hazardous conditions are the triggering mechanism for the issuance of advisories. They also use the reports for pilot weather briefings.
                            5. The NWS, other government organizations, the military, and private industry groups use PIREP s for research activities in the study of meteorological phenomena.
                            6. All air traffic facilities and the NWS forward the reports received from pilots into the weather distribution system to assure the information is made available to all pilots and other interested parties.
                            1. KCMH UA /OV APE 230010/TM 1516/FL085/TP BE20/SK BKN065/WX FV03SM HZ FU/TA 20/TB LGT
                            1. One zero miles southwest of Appleton VOR; time 1516 UTC; altitude eight thousand five hundred; aircraft type BE200; bases of the broken cloud layer is six thousand five hundred; flight visibility 3 miles with haze and smoke; air temperature 20 degrees Celsius; light turbulence.

                            EXAMPLE-

                            1. KCRW UV /OV KBKW 360015-KCRW/TM 1815/FL120//TP BE99/SK IMC/WX RA/TA M08 /WV 290030/TB LGT-MDT/IC LGT RIME/RM MDT MXD ICG DURC KROA NWBND FL080-100 1750Z
                            1. From 15 miles north of Beckley VOR to Charleston VOR; time 1815 UTC; altitude 12,000 feet; type aircraft, BE-99; in clouds; rain; temperature minus 8 Celsius; wind 290 degrees magnetic at 30 knots; light to moderate turbulence; light rime icing during climb northwestbound from Roanoke, VA, between 8,000 and 10,000 feet at 1750 UTC.
                            TBL 7-1-8
                            PIREP Element Code Chart
                            PIREP ELEMENT PIREP CODE CONTENTS
                            1. 3-letter station identifier XXX Nearest weather reporting location to the reported phenomenon
                            2. Report type UA or UUA Routine or Urgent PIREP
                            3. Location /OV In relation to a VOR
                            4. Time /TM Coordinated Universal Time
                            5. Altitude /FL Essential for turbulence and icing reports
                            6. Type Aircraft /TP Essential for turbulence and icing reports
                            7. Sky cover /SK Cloud height and coverage (sky clear, few, scattered, broken, or overcast)
                            8. Weather /WX Flight visibility, precipitation, restrictions to visibility, etc.
                            9. Temperature /TA Degrees Celsius
                            10. Wind /WV Direction in degrees magnetic north and speed in knots
                            11. Turbulence /TB See AIM paragraph 7-1-21
                            12. Icing /IC See AIM paragraph 7-1-19
                            13. Remarks /RM For reporting elements not included or to clarify previously reported items

                            NOTE- Severe icing is aircraft dependent, as are the other categories of icing intensity. Severe icing may occur at any ice accumulation rate when the icing rate or ice accumulations exceed the tolerance of the aircraft.

                            EXAMPLE- Pilot report: give aircraft identification, location, time (UTC), intensity of type, altitude/FL, aircraft type, indicated air speed (IAS), and outside air temperature (OAT).

                            1. Rime ice. Rough, milky, opaque ice formed by the instantaneous freezing of small supercooled water droplets.
                            2. Clear ice. A glossy, clear, or translucent ice formed by the relatively slow freezing of large supercooled water droplets.
                            3. The OAT should be requested by the FSS or ATC if not included in the PIREP .
                            TBL 7-1-9
                            Icing Types
                            Clear Ice See Glaze Ice.
                            Glaze Ice Ice, sometimes clear and smooth, but usually containing some air pockets, which results in a lumpy translucent appearance. Glaze ice results from supercooled drops/droplets striking a surface but not freezing rapidly on contact. Glaze ice is denser, harder, and sometimes more transparent than rime ice. Factors, which favor glaze formation, are those that favor slow dissipation of the heat of fusion (i.e., slight supercooling and rapid accretion). With larger accretions, the ice shape typically includes “horns” protruding from unprotected leading edge surfaces. It is the ice shape, rather than the clarity or color of the ice, which is most likely to be accurately assessed from the cockpit. The terms “clear” and “glaze” have been used for essentially the same type of ice accretion, although some reserve “clear” for thinner accretions which lack horns and conform to the airfoil.
                            Intercycle Ice Ice which accumulates on a protected surface between actuation cycles of a deicing system.
                            Known or Observed or Detected Ice Accretion Actual ice observed visually to be on the aircraft by the flight crew or identified by on-board sensors.
                            Mixed Ice Simultaneous appearance or a combination of rime and glaze ice characteristics. Since the clarity, color, and shape of the ice will be a mixture of rime and glaze characteristics, accurate identification of mixed ice from the cockpit may be difficult.
                            Residual Ice Ice which remains on a protected surface immediately after the actuation of a deicing system.
                            Rime Ice A rough, milky, opaque ice formed by the rapid freezing of supercooled drops/droplets after they strike the aircraft. The rapid freezing results in air being trapped, giving the ice its opaque appearance and making it porous and brittle. Rime ice typically accretes along the stagnation line of an airfoil and is more regular in shape and conformal to the airfoil than glaze ice. It is the ice shape, rather than the clarity or color of the ice, which is most likely to be accurately assessed from the cockpit.
                            Runback Ice Ice which forms from the freezing or refreezing of water leaving protected surfaces and running back to unprotected surfaces.
                            Note-
                            Ice types are difficult for the pilot to discern and have uncertain effects on an airplane in flight. Ice type definitions will be included in the AIM for use in the “Remarks” section of the PIREP and for use in forecasting.
                            TBL 7-1-10
                            Icing Conditions
                            1. Over Omaha, 1232Z, moderate turbulence in clouds at Flight Level three one zero, Boeing 707.
                            2. From five zero miles south of Albuquerque to three zero miles north of Phoenix, 1250Z, occasional moderate chop at Flight Level three three zero, DC8.
                            TBL 7-1-11
                            Turbulence Reporting Criteria Table
                            Intensity Aircraft Reaction Reaction Inside Aircraft Reporting Term-Definition
                            Light Turbulence that momentarily causes slight, erratic changes in altitude and/or attitude (pitch, roll, yaw). Report as Light Turbulence; 1 or Turbulence that causes slight, rapid and somewhat rhythmic bumpiness without appreciable changes in altitude or attitude. Report as Light Chop. Occupants may feel a slight strain against seat belts or shoulder straps. Unsecured objects may be displaced slightly. Food service may be conducted and little or no difficulty is encountered in walking. Occasional-Less than 1 /3 of the time. Intermittent- 1 /3 to 2 /3. Continuous-More than 2 /3.
                            Moderate Turbulence that is similar to Light Turbulence but of greater intensity. Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times. It usually causes variations in indicated airspeed. Report as Moderate Turbulence; 1
                            or
                            Turbulence that is similar to Light Chop but of greater intensity. It causes rapid bumps or jolts without appreciable changes in aircraft altitude or attitude. Report as Moderate Chop. 1                            		 Occupants feel definite strains against seat belts or shoulder straps. Unsecured objects are dislodged. Food service and walking are difficult. NOTE 1. Pilots should report location(s), time (UTC), intensity, whether in or near clouds, altitude, type of aircraft and, when applicable, duration of turbulence. 2. Duration may be based on time between two locations or over a single location. All locations should be readily identifiable.
                            Severe Turbulence that causes large, abrupt changes in altitude and/or attitude. It usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control. Report as Severe Turbulence. 1 Occupants are forced violently against seat belts or shoulder straps. Unsecured objects are tossed about. Food Service and walking are impossible. EXAMPLES: a. Over Omaha. 1232Z, Moderate Turbulence, in cloud, Flight Level 310, B707.
                            Extreme Turbulence in which the aircraft is violently tossed about and is practically impossible to control. It may cause structural damage. Report as Extreme Turbulence. 1 b. From 50 miles south of Albuquerque to 30 miles north of Phoenix, 1210Z to 1250Z, occasional Moderate Chop, Flight Level 330, DC8.
                            1 High level turbulence (normally above 15,000 feet ASL) not associated with cumuliform cloudiness, including thunderstorms, should be reported as CAT (clear air turbulence) preceded by the appropriate intensity, or light or moderate chop.
                            1. Denver Tower, Cessna 1234 encountered wind shear, loss of 20 knots at 400.
                            2. Tulsa Tower, American 721 encountered wind shear on final, gained 25 knots between 600 and 400 feet followed by loss of 40 knots between 400 feet and surface.
                            1. Pilots who are not able to report wind shear in these specific terms are encouraged to make reports in terms of the effect upon their aircraft.

                            EXAMPLE- Miami Tower, Gulfstream 403 Charlie encountered an abrupt wind shear at 800 feet on final, max thrust required.

                            EXAMPLE- “Denver Tower, United 1154, wind shear escape."

                            EXAMPLE- “Denver Tower, United ll54, wind shear escape complete, resuming last assigned heading/(name) DP /clearance."
                            or
                            “Denver Tower, United ll54, wind shear escape complete, request further instructions."

                            REFERENCE- AIM, Para 7-1-21, PIREP s Relating to Turbulence.
                            1. Relatively recent meteorological studies have confirmed the existence of microburst phenomenon. Microbursts are small scale intense downdrafts which, on reaching the surface, spread outward in all directions from the downdraft center. This causes the presence of both vertical and horizontal wind shears that can be extremely hazardous to all types and categories of aircraft, especially at low altitudes. Due to their small size, short life span, and the fact that they can occur over areas without surface precipitation, microbursts are not easily detectable using conventional weather radar or wind shear alert systems.
                            2. Parent clouds producing microburst activity can be any of the low or middle layer convective cloud types. Note, however, that microbursts commonly occur within the heavy rain portion of thunderstorms, and in much weaker, benign appearing convective cells that have little or no precipitation reaching the ground.
                            FIG 7-1-13
                            Evolution of a Microburst

                            A graphic depicting the different stages of a microburst.

                          5. The life cycle of a microburst as it descends in a convective rain shaft is seen in FIG 7-1-13. An important consideration for pilots is the fact that the microburst intensifies for about 5 minutes after it strikes the ground.
                          6. Characteristics of microbursts include:
                            1. Size. The microburst downdraft is typically less than 1 mile in diameter as it descends from the cloud base to about 1,000-3,000 feet above the ground. In the transition zone near the ground, the downdraft changes to a horizontal outflow that can extend to approximately 2 1 /2 miles in diameter.
                            2. Intensity. The downdrafts can be as strong as 6,000 feet per minute. Horizontal winds near the surface can be as strong as 45 knots resulting in a 90 knot shear (headwind to tailwind change for a traversing aircraft) across the microburst. These strong horizontal winds occur within a few hundred feet of the ground.
                            3. Visual Signs. Microbursts can be found almost anywhere that there is convective activity. They may be embedded in heavy rain associated with a thunderstorm or in light rain in benign appearing virga. When there is little or no precipitation at the surface accompanying the microburst, a ring of blowing dust may be the only visual clue of its existence.
                            4. Duration. An individual microburst will seldom last longer than 15 minutes from the time it strikes the ground until dissipation. The horizontal winds continue to increase during the first 5 minutes with the maximum intensity winds lasting approximately 2-4 minutes. Sometimes microbursts are concentrated into a line structure, and under these conditions, activity may continue for as long as an hour. Once microburst activity starts, multiple microbursts in the same general area are not uncommon and should be expected.

                            FIG 7-1-14
                            Microburst Encounter During Takeoff

                            A graphic depicting a microburst encounter during takeoff.

                          Microburst wind shear may create a severe hazard for aircraft within 1,000 feet of the ground, particularly during the approach to landing and landing and take‐off phases. The impact of a microburst on aircraft which have the unfortunate experience of penetrating one is characterized in FIG 7-1-14. The aircraft may encounter a headwind (performance increasing) followed by a downdraft and tailwind (both performance decreasing), possibly resulting in terrain impact.

                          FIG 7-1-15
                          NAS Wind Shear Product Systems
                          1. FAA's Integrated Wind Shear Detection Plan.
                            1. The FAA currently employs an integrated plan for wind shear detection that will significantly improve both the safety and capacity of the majority of the airports currently served by the air carriers. This plan integrates several programs, such as the Integrated Terminal Weather System (ITWS), Terminal Doppler Weather Radar (TDWR), Weather Systems Processor (WSP), and Low Level Wind Shear Alert Systems (LLWAS) into a single strategic concept that significantly improves the aviation weather information in the terminal area. (See FIG 7-1-15.)
                            2. The wind shear/microburst information and warnings are displayed on the ribbon display terminals (RBDT) located in the tower cabs. They are identical (and standardized) in the LLWAS, TDWR and WSP systems, and so designed that the controller does not need to interpret the data, but simply read the displayed information to the pilot. The RBDTs are constantly monitored by the controller to ensure the rapid and timely dissemination of any hazardous event(s) to the pilot.
                            FIG 7-1-16
                            LLWAS Siting Criteria

                            A graphic depicting the siting criteria for the Low Level Wind Shear Alert System.

                          2. The early detection of a wind shear/micro-burst event, and the subsequent warning(s) issued to an aircraft on approach or departure, will alert the pilot/crew to the potential of, and to be prepared for, a situation that could become very dangerous! Without these warnings, the aircraft may NOT be able to climb out of, or safely transition, the event, resulting in a catastrophe. The air carriers, working with the FAA, have developed specialized training programs using their simulators to train and prepare their pilots on the demanding aircraft procedures required to escape these very dangerous wind shear and/or microburst encounters.
                        2. Low Level Wind Shear Alert System (LLWAS).
                          1. The LLWAS provides wind data and software processes to detect the presence of hazardous wind shear and microbursts in the vicinity of an airport. Wind sensors, mounted on poles sometimes as high as 150 feet, are (ideally) located 2,000 - 3,500 feet, but not more than 5,000 feet, from the centerline of the runway. (See FIG 7-1-16.)

                            FIG 7-1-17
                            Warning Boxes

                            A graphic of the theoretical view of the runway and the warning boxes that the software uses to determine the location(s) of wind shear or microbursts.

                          2. LLWAS was fielded in 1988 at 110 airports across the nation. Many of these systems have been replaced by new TDWR and WSP technology. While all legacy LLWAS systems will eventually be phased out, 39 airports will be upgraded to LLWAS-NE (Network Expansion) system. The new LLWAS-NE systems not only provide the controller with wind shear warnings and alerts, including wind shear/microburst detection at the airport wind sensor location, but also provide the location of the hazards relative to the airport runway(s). It also has the flexibility and capability to grow with the airport as new runways are built. As many as 32 sensors, strategically located around the airport and in relationship to its runway configuration, can be accommodated by the LLWAS-NE network.
                        3. Terminal Doppler Weather Radar (TDWR).
                          1. TDWRs have been deployed at 45 locations across the U.S. Optimum locations for TDWRs are 8 to 12 miles off of the airport proper, and designed to look at the airspace around and over the airport to detect microbursts, gust fronts, wind shifts, and precipitation intensities. TDWR products advise the controller of wind shear and microburst events impacting all runways and the areas 1 /2 mile on either side of the extended centerline of the runways out to 3 miles on final approach and 2 miles out on departure. (FIG 7-1-17 is a theoretical view of the warning boxes, including the runway, that the software uses in determining the location(s) of wind shear or microbursts). These warnings are displayed (as depicted in the examples in subparagraph 5) on the RBDT.
                          2. It is very important to understand what TDWR does NOT DO:
                            1. It DOES NOT warn of wind shear outside of the alert boxes (on the arrival and departure ends of the runways);
                            2. It DOES NOT detect wind shear that is NOT a microburst or a gust front;
                            3. It DOES NOT detect gusty or cross wind conditions; and
                            4. It DOES NOT detect turbulence.
                              However, research and development is continuing on these systems. Future improvements may include such areas as storm motion (movement), improved gust front detection, storm growth and decay, microburst prediction, and turbulence detection.
                          3. TDWR also provides a geographical situation display (GSD) for supervisors and traffic management specialists for planning purposes. The GSD displays (in color) 6 levels of weather (precipitation), gust fronts and predicted storm movement(s). This data is used by the tower supervisor(s), traffic management specialists and controllers to plan for runway changes and arrival/departure route changes in order to both reduce aircraft delays and increase airport capacity.
                        4. Weather Systems Processor (WSP).
                          1. The WSP provides the controller, supervisor, traffic management specialist, and ultimately the pilot, with the same products as the terminal doppler weather radar (TDWR) at a fraction of the cost of a TDWR. This is accomplished by utilizing new technologies to access the weather channel capabilities of the existing ASR -9 radar located on or near the airport, thus eliminating the requirements for a separate radar location, land acquisition, support facilities and the associated communication landlines and expenses.
                          2. The WSP utilizes the same RBDT display as the TDWR and LLWAS, and, just like TDWR, also has a GSD for planning purposes by supervisors, traffic management specialists and controllers. The WSP GSD emulates the TDWR display, i.e., it also depicts 6 levels of precipitation, gust fronts and predicted storm movement, and like the TDWR GSD, is used to plan for runway changes and arrival/departure route changes in order to reduce aircraft delays and to increase airport capacity.
                          3. This system is installed at 34 airports across the nation, substantially increasing the safety of flying.
                        5. Operational aspects of LLWAS, TDWR and WSP.
                          To demonstrate how this data is used by both the controller and the pilot, 3 ribbon display examples and their explanations are presented:
                          1. MICROBURST ALERTS

                            EXAMPLE- This is what the controller sees on his/her ribbon display in the tower cab.
                            27A MBA 35K- 2MF 250 20
                            NOTE- (See FIG 7-1-18 to see how the TDWR/WSP determines the microburst location). This is what the controller will say when issuing the alert. PHRASEOLOGY- RUNWAY 27 ARRIVAL, MICROBURST ALERT, 35 KT LOSS 2 MILE FINAL, THRESHOLD WIND 250 AT 20.

                            In plain language, the controller is telling the pilot that on approach to runway 27, there is a microburst alert on the approach lane to the runway, and to anticipate or expect a 35 knot loss of airspeed at approximately 2 miles out on final approach (where it will first encounter the phenomena). With that information, the aircrew is forewarned, and should be prepared to apply wind shear/microburst escape procedures should they decide to continue the approach. Additionally, the surface winds at the airport for landing runway 27 are reported as 250 degrees at 20 knots.

                            NOTE- Threshold wind is at pilot's request or as deemed appropriate by the controller.

                            REFERENCE- FAA Order JO 7110.65, Para 3-1-8b2(a), Air Traffic Control, Low Level Wind Shear/Microburst Advisories.

                            FIG 7-1-18
                            Microburst Alert

                            A graphic depicting a microburst alert.

                            WIND SHEAR ALERTS

                            EXAMPLE- This is what the controller sees on his/her ribbon display in the tower cab.
                            27A WSA 20K- 3MF 200 15
                            NOTE- (See FIG 7-1-19 to see how the TDWR/WSP determines the wind shear location). This is what the controller will say when issuing the alert. PHRASEOLOGY- RUNWAY 27 ARRIVAL, WIND SHEAR ALERT, 20 KT LOSS 3 MILE FINAL, THRESHOLD WIND 200 AT 15.

                            In plain language, the controller is advising the aircraft arriving on runway 27 that at about 3 miles out they can expect to encounter a wind shear condition that will decrease their airspeed by 20 knots and possibly encounter turbulence. Additionally, the airport surface winds for landing runway 27 are reported as 200 degrees at 15 knots.

                            NOTE- Threshold wind is at pilot's request or as deemed appropriate by the controller.

                            REFERENCE- FAA Order JO 7110.65, Para 3-1-8, Low Level Wind Shear/Microburst Advisories, Subpara b2(a).

                            FIG 7-1-19
                            Weak Microburst Alert

                            A graphic depicting a weak microburst alert.

                            FIG 7-1-20
                            Gust Front Alert

                            A graphic depicting a gust front alert.

                            MULTIPLE WIND SHEAR ALERTS

                            EXAMPLE- This is what the controller sees on his/her ribbon display in the tower cab.
                            27A WSA 20K+ RWY 250 20
                            27D WSA 20K+ RWY 250 20
                            NOTE- (See FIG 7-1-20 to see how the TDWR/WSP determines the gust front/wind shear location.) This is what the controller will say when issuing the alert.

                            PHRASEOLOGY- MULTIPLE WIND SHEAR ALERTS. RUNWAY 27 ARRIVAL, WIND SHEAR ALERT, 20 KT GAIN ON RUNWAY; RUNWAY 27 DEPARTURE, WIND SHEAR ALERT, 20 KT GAIN ON RUNWAY, WIND 250 AT 20.

                            EXAMPLE- In this example, the controller is advising arriving and departing aircraft that they could encounter a wind shear condition right on the runway due to a gust front (significant change of wind direction) with the possibility of a 20 knot gain in airspeed associated with the gust front. Additionally, the airport surface winds (for the runway in use) are reported as 250 degrees at 20 knots.

                            REFERENCE- FAA Order 7110.65, Para 3-1-8, Low Level Wind Shear/Microburst Advisories, Subpara b2(d). FIG 7-1-21
                            TWIP Image of Convective Weather at MCO International

                            A graphic depicting the TWIP capability.

                          2. TWIP products are generated using weather data from the TDWR or the Integrated Terminal Weather System (ITWS). These products can then be accessed by pilots using the Aircraft Communications Addressing and Reporting System (ACARS) data link services. Airline dispatchers can also access this database and send messages to specific aircraft whenever wind shear activity begins or ends at an airport.
                          3. TWIP products include descriptions and character graphics of microburst alerts, wind shear alerts, significant precipitation, convective activity within 30 NM surrounding the terminal area, and expected weather that will impact airport operations. During inclement weather, i.e., whenever a predetermined level of precipitation or wind shear is detected within 15 miles of the terminal area, TWIP products are updated once each minute for text messages and once every five minutes for character graphic messages. During good weather (below the predetermined precipitation or wind shear parameters) each message is updated every 10 minutes. These products are intended to improve the situational awareness of the pilot/flight crew, and to aid in flight planning prior to arriving or departing the terminal area. It is important to understand that, in the context of TWIP, the predetermined levels for inclement versus good weather has nothing to do with the criteria for VFR/MVFR/IFR/LIFR; it only deals with precipitation, wind shears and microbursts.

                            TBL 7-1-12
                            TWIP-Equipped Airports
                            Airport Identifier
                            Andrews AFB, MD KADW
                            Hartsfield-Jackson Atlanta Intl Airport KATL
                            Nashville Intl Airport KBNA
                            Logan Intl Airport KBOS
                            Baltimore/Washington Intl Airport KBWI
                            Hopkins Intl Airport KCLE
                            Charlotte/Douglas Intl Airport KCLT
                            Port Columbus Intl Airport KCMH
                            Cincinnati/Northern Kentucky Intl Airport KCVG
                            Dallas Love Field Airport KDAL
                            James M. Cox Intl Airport KDAY
                            Ronald Reagan Washington National Airport KDCA
                            Denver Intl Airport KDEN
                            Dallas-Fort Worth Intl Airport KDFW
                            Detroit Metro Wayne County Airport KDTW
                            Newark Liberty Intl Airport KEWR
                            Fort Lauderdale-Hollywood Intl Airport KFLL
                            William P. Hobby Airport KHOU
                            Washington Dulles Intl Airport KIAD
                            George Bush Intercontinental Airport KIAH
                            Wichita Mid-Continent Airport KICT
                            Indianapolis Intl Airport KIND
                            John F. Kennedy Intl Airport KJFK
                            Harry Reid Intl Airport KLAS
                            LaGuardia Airport KLGA
                            Kansas City Intl Airport KMCI
                            Orlando Intl Airport KMCO
                            Midway Intl Airport KMDW
                            Memphis Intl Airport KMEM
                            Miami Intl Airport KMIA
                            General Mitchell Intl Airport KMKE
                            Minneapolis St. Paul Intl Airport KMSP
                            Louis Armstrong New Orleans Intl Airport KMSY
                            Will Rogers World Airport KOKC
                            O'Hare Intl Airport KORD
                            Palm Beach Intl Airport KPBI
                            Philadelphia Intl Airport KPHL
                            Phoenix Sky Harbor Intl Airport KPHX
                            Pittsburgh Intl Airport KPIT
                            Raleigh-Durham Intl Airport KRDU
                            Louisville Intl Airport KSDF
                            Salt Lake City Intl Airport KSLC
                            Lambert-St. Louis Intl Airport KSTL
                            Tampa Intl Airport KTPA
                            Tulsa Intl Airport KTUL
                            Luis Munoz Marin Intl Airport TJSJ
                            1. Volcanic eruptions which send ash into the upper atmosphere occur somewhere around the world several times each year. Flying into a volcanic ash cloud can be extremely dangerous. At least two B747s have lost all power in all four engines after such an encounter. Regardless of the type aircraft, some damage is almost certain to ensue after an encounter with a volcanic ash cloud. Additionally, studies have shown that volcanic eruptions are the only significant source of large quantities of sulphur dioxide (SO2) gas at jet-cruising altitudes. Therefore, the detection and subsequent reporting of SO2 is of significant importance. Although SO2 is colorless, its presence in the atmosphere should be suspected when a sulphur-like or rotten egg odor is present throughout the cabin.
                            2. While some volcanoes in the U.S. are monitored, many in remote areas are not. These unmonitored volcanoes may erupt without prior warning to the aviation community. A pilot observing a volcanic eruption who has not had previous notification of it may be the only witness to the eruption. Pilots are strongly encouraged to transmit a PIREP regarding volcanic eruptions and any observed volcanic ash clouds or detection of sulphur dioxide (SO2) gas associated with volcanic activity.
                            3. Pilots should submit PIREP s regarding volcanic activity using the Volcanic Activity Reporting (VAR) form as illustrated in Appendix 2. If a VAR form is not immediately available, relay enough information to identify the position and type of volcanic activity.
                            4. Pilots should verbally transmit the data required in items 1 through 8 of the VAR as soon as possible. The data required in items 9 through 16 of the VAR should be relayed after landing if possible.
                            REFERENCE- Pilot/Controller Glossary- Precipitation Radar Weather Descriptions
                            1. Alert provided by an ATC facility to an aircraft:
                              (aircraft identification) EXTREME precipitation between ten o'clock and two o'clock, one five miles. Precipitation area is two five miles in diameter.
                            2. Alert provided by an FSS :
                              (aircraft identification) EXTREME precipitation two zero miles west of Atlanta V-O-R, two five miles wide, moving east at two zero knots, tops flight level three niner zero.
                            1. Thunderstorm Avoidance. Never regard any thunderstorm lightly, even when radar echoes are of light intensity. Avoiding thunderstorms is the best policy. Following are some Do's and Don'ts of thunderstorm avoidance:
                              1. Don't land or takeoff in the face of an approaching thunderstorm. A sudden gust front of low level turbulence could cause loss of control.
                              2. Don't attempt to fly under a thunderstorm even if you can see through to the other side. Turbulence and wind shear under the storm could be hazardous.
                              3. Don't attempt to fly under the anvil of a thunderstorm. There is a potential for severe and extreme clear air turbulence.
                              4. Don't fly without airborne radar into a cloud mass containing scattered embedded thunderstorms. Scattered thunderstorms not embedded usually can be visually circumnavigated.
                              5. Don't trust the visual appearance to be a reliable indicator of the turbulence inside a thunderstorm.
                              6. Don't assume that ATC will offer radar navigation guidance or deviations around thunderstorms.
                              7. Don't use data-linked weather next generation weather radar (NEXRAD) mosaic imagery as the sole means for negotiating a path through a thunderstorm area (tactical maneuvering).
                              8. Do remember that the data-linked NEXRAD mosaic imagery shows where the weather was, not where the weather is. The weather conditions depicted may be 15 to 20 minutes older than indicated on the display.
                              9. Do listen to chatter on the ATC frequency for Pilot Weather Reports ( PIREP ) and other aircraft requesting to deviate or divert.
                              10. Do ask ATC for radar navigation guidance or to approve deviations around thunderstorms, if needed.
                              11. Do use data-linked weather NEXRAD mosaic imagery (for example, Flight Information Service-Broadcast ( FIS-B )) for route selection to avoid thunderstorms entirely (strategic maneuvering).
                              12. Do advise ATC, when switched to another controller, that you are deviating for thunderstorms before accepting to rejoin the original route.
                              13. Do ensure that after an authorized weather deviation, before accepting to rejoin the original route, that the route of flight is clear of thunderstorms.
                              14. Do avoid by at least 20 miles any thunderstorm identified as severe or giving an intense radar echo. This is especially true under the anvil of a large cumulonimbus.
                              15. Do circumnavigate the entire area if the area has 6/10 thunderstorm coverage.
                              16. Do remember that vivid and frequent lightning indicates the probability of a severe thunderstorm.
                              17. Do regard as extremely hazardous any thunderstorm with tops 35,000 feet or higher whether the top is visually sighted or determined by radar.
                              18. Do give a PIREP for the flight conditions.
                              19. Do divert and wait out the thunderstorms on the ground if unable to navigate around an area of thunderstorms.
                              20. Do contact Flight Service for assistance in avoiding thunderstorms. Flight Service specialists have NEXRAD mosaic radar imagery and NEXRAD single site radar with unique features such as base and composite reflectivity, echo tops, and VAD wind profiles.
                              1. Tighten your safety belt, put on your shoulder harness (if installed), if and secure all loose objects.
                              2. Plan and hold the course to take the aircraft through the storm in a minimum time.
                              3. To avoid the most critical icing, establish a penetration altitude below the freezing level or above the level of -15ºC.
                              4. Verify that pitot heat is on and turn on carburetor heat or jet engine anti-ice. Icing can be rapid at any altitude and cause almost instantaneous power failure and/or loss of airspeed indication.
                              5. Establish power settings for turbulence penetration airspeed recommended in the aircraft manual.
                              6. Turn up cockpit lights to highest intensity to lessen temporary blindness from lightning.
                              7. If using automatic pilot, disengage Altitude Hold Mode and Speed Hold Mode. The automatic altitude and speed controls will increase maneuvers of the aircraft thus increasing structural stress.
                              8. If using airborne radar, tilt the antenna up and down occasionally. This will permit the detection of other thunderstorm activity at altitudes other than the one being flown.
                              1. Do keep your eyes on your instruments. Looking outside the cockpit can increase danger of temporary blindness from lightning.
                              2. Don't change power settings; maintain settings for the recommended turbulence penetration airspeed.
                              3. Do maintain constant attitude. Allow the altitude and airspeed to fluctuate.
                              4. Don't turn back once you are in the thunderstorm. A straight course through the storm most likely will get the aircraft out of the hazards most quickly. In addition, turning maneuvers increase stress on the aircraft.
                              FIG 7-1-22
                              Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR) (Front)

                              A graphic depicting the front of the Key to the Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR).

                              FIG 7-1-23
                              Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR) (Back)

                              A graphic depicting the back of the Key to the Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR).

                            2. International Civil Aviation Organization (ICAO) Weather Formats The U.S. uses the ICAO world standard for aviation weather reporting and forecasting. The World Meteorological Organization's (WMO) publication No. 782 “Aerodrome Reports and Forecasts” contains the base METAR and TAF code as adopted by the WMO member countries.
                              1. Although the METAR code is adopted worldwide, each country is allowed to make modifications or exceptions to the code for use in their particular country, e.g., the U.S. will continue to use statute miles for visibility, feet for RVR values, knots for wind speed, and inches of mercury for altimetry. However, temperature and dew point will be reported in degrees Celsius. The U.S reports prevailing visibility rather than lowest sector visibility. The elements in the body of a METAR report are separated with a space. The only exceptions are RVR, temperature, and dew point which are separated with a solidus (/). When an element does not occur, or cannot be observed, the preceding space and that element are omitted from that particular report. A METAR report contains the following sequence of elements in the following order:
                                1. Type of report.
                                2. ICAO Station Identifier.
                                3. Date and time of report.
                                4. Modifier (as required).
                                5. Wind.
                                6. Visibility.
                                7. Runway Visual Range (RVR).
                                8. Weather phenomena.
                                9. Sky conditions.
                                10. Temperature/dew point group.
                                11. Altimeter.
                                12. Remarks (RMK).
                              2. The following paragraphs describe the elements in a METAR report.
                                1. Type of report. There are two types of report:
                                  1. Aviation Routine Weather Report (METAR); and
                                  2. Nonroutine (Special) Aviation Weather Report (SPECI).
                                    The type of report (METAR or SPECI) will always appear as the lead element of the report.
                                2. ICAO Station Identifier. The METAR code uses ICAO 4-letter station identifiers. In the contiguous 48 States, the 3-letter domestic station identifier is prefixed with a “K;” i.e., the domestic identifier for Seattle is SEA while the ICAO identifier is KSEA. Elsewhere, the first two letters of the ICAO identifier indicate what region of the world and country (or state) the station is in. For Alaska, all station identifiers start with “PA;” for Hawaii, all station identifiers start with “PH.” Canadian station identifiers start with “CU,” “CW,” “CY,” and “CZ.” Mexican station identifiers start with “ MM .” The identifier for the western Caribbean is “M” followed by the individual country's letter; i.e., Cuba is “MU;” Dominican Republic “MD;” the Bahamas “MY.” The identifier for the eastern Caribbean is “T” followed by the individual country's letter; i.e., Puerto Rico is “TJ.” For a complete worldwide listing see ICAO Document 7910, Location Indicators.
                                3. Date and Time of Report. The date and time the observation is taken are transmitted as a six-digit date/time group appended with Z to denote Coordinated Universal Time (UTC). The first two digits are the date followed with two digits for hour and two digits for minutes.

                                  EXAMPLE- 172345Z (the 17 th day of the month at 2345Z)

                                  NOTE- There are two types of automated stations, AO1 for automated weather reporting stations without a precipitation discriminator, and AO2 for automated stations with a precipitation discriminator. (A precipitation discriminator can determine the difference between liquid and frozen/freezing precipitation). This information appears in the remarks section of an automated report.

                                  EXAMPLE- 13008KT - wind from 130 degrees at 8 knots
                                  08032G45KT - wind from 080 degrees at 32 knots with gusts to 45 knots
                                  VRB04KT - wind variable in direction at 4 knots
                                  00000KT - wind calm
                                  210103G130KT - wind from 210 degrees at 103 knots with gusts to 130 knots
                                  If the wind direction is variable by 60 degrees or more and the speed is greater than 6 knots, a variable group consisting of the extremes of the wind direction separated by a “v” will follow the prevailing wind group.
                                  32012G22KT 280V350

                                  1. Peak Wind. Whenever the peak wind exceeds 25 knots “PK WND” will be included in Remarks, e.g., PK WND 28045/1955 “Peak wind two eight zero at four five occurred at one niner five five.” If the hour can be inferred from the report time, only the minutes will be appended, e.g., PK WND 34050/38 “Peak wind three four zero at five zero occurred at three eight past the hour.”
                                  2. Wind shift. Whenever a wind shift occurs, “WSHFT” will be included in remarks followed by the time the wind shift began, e.g., WSHFT 30 FROPA “Wind shift at three zero due to frontal passage.”
                                  EXAMPLE- 7SM - seven statute miles
                                  15SM - fifteen statute miles
                                  1 /2SM - one-half statute mile
                                  1. Tower/surface visibility. If either visibility (tower or surface) is below four statute miles, the lesser of the two will be reported in the body of the report; the greater will be reported in remarks.
                                  2. Automated visibility. ASOS/AWOS visibility stations will show visibility 10 or greater than 10 miles as “10SM.” AWOS visibility stations will show visibility less than 1 /4 statute mile as “M 1 /4SM” and visibility 10 or greater than 10 miles as “10SM.”

                                  NOTE- Automated sites that are augmented by human observer to meet service level requirements can report 0, 1/16 SM, and 1/8 SM visibility increments.

                                  EXAMPLE- VIS N2 - visibility north two

                                  EXAMPLE- R32L/1200FT - runway three two left R-V-R one thousand two hundred.
                                  R27R/M1000V4000FT - runway two seven right R-V-R variable from less than one thousand to four thousand.

                                  NOTE- The “/” above and in the following descriptions (except as the separator between the temperature and dew point) are for separation purposes in this publication and do not appear in the actual METARs.

                                  1. Intensity applies only to the first type of precipitation reported. A “-” denotes light, no symbol denotes moderate, and a “+” denotes heavy.
                                  2. Proximity applies to and reported only for weather occurring in the vicinity of the airport (between 5 and 10 miles of the point(s) of observation). It is denoted by the letters “VC.” (Intensity and “VC” will not appear together in the weather group).
                                  3. Descriptor. These eight descriptors apply to the precipitation or obstructions to visibility:
                                  TS thunderstorm
                                  DR low drifting
                                  SH showers
                                  MI shallow
                                  FZ freezing
                                  BC patches
                                  BL blowing
                                  PR partial

                                  NOTE- Although “TS” and “SH” are used with precipitation and may be preceded with an intensity symbol, the intensity still applies to the precipitation, not the descriptor.

                                  RA rain
                                  DZ drizzle
                                  SN snow
                                  GR hail ( 1 /4” or greater)
                                  GS small hail/snow pellets
                                  PL ice pellets
                                  SG snow grains
                                  IC ice crystals (diamond dust)
                                  UP unknown precipitation (automated stations only)
                                  FG fog (vsby less than 5 /8 mile)
                                  HZ haze
                                  FU smoke
                                  PY spray
                                  BR mist (vsby 5 /8 - 6 miles)
                                  SA sand
                                  DU dust
                                  VA volcanic ash

                                  NOTE- Fog (FG) is observed or forecast only when the visibility is less than five-eighths of mile, otherwise mist (BR) is observed or forecast.

                                  SQ squall
                                  SS sandstorm
                                  DS duststorm
                                  PO dust/sand whirls
                                  FC funnel cloud
                                  +FC tornado/waterspout
                                  EXAMPLES-
                                  TSRA thunderstorm with moderate rain
                                  + SN heavy snow
                                  -RA FG light rain and fog
                                  BRHZ mist and haze (visibility 5 /8 mile or greater)
                                  FZDZ freezing drizzle
                                  VCSH rain shower in the vicinity
                                  +SHRASNPL heavy rain showers, snow, ice pellets (intensity indicator refers to the predominant rain)

                                    Amount. The amount of sky cover is reported in eighths of sky cover, using the contractions:

                                  SKC clear (no clouds)
                                  FEW >0 to 2 /8
                                  SCT scattered ( 3 /8s to 4 /8s of clouds)
                                  BKN broken ( 5 /8s to 7 /8s of clouds)
                                  OVC overcast ( 8 /8s clouds)
                                  CB Cumulonimbus when present
                                  TCU Towering cumulus when present
                                  1. “SKC” will be reported at manual stations. “CLR” will be used at automated stations when no clouds below 12,000 feet are reported.
                                  2. A ceiling layer is not designated in the METAR code. For aviation purposes, the ceiling is the lowest broken or overcast layer, or vertical visibility into an obscuration. Also there is no provision for reporting thin layers in the METAR code. When clouds are thin, that layer must be reported as if it were opaque.

                                  EXAMPLE- (Reported as) SCT025TCU BKN080 BKN250 (spoken as) “TWO THOUSAND FIVE HUNDRED SCATTERED TOWERING CUMULUS, CEILING EIGHT THOUSAND BROKEN, TWO FIVE THOUSAND BROKEN.”
                                  (Reported as) SCT008 OVC012CB (spoken as) “EIGHT HUNDRED SCATTERED CEILING ONE THOUSAND TWO HUNDRED OVERCAST CUMULONIMBUS CLOUDS.”

                                  EXAMPLE- 1 /8 SM FG VV006 - visibility one eighth, fog, indefinite ceiling six hundred.

                                  EXAMPLE- BKN000 (in body) - “sky partially obscured”
                                  FU BKN000 (in remarks) - “smoke obscuring five- to seven-eighths of the sky”

                                  EXAMPLE- BKN020 (in body) - “ceiling two thousand broken”
                                  RMK FU BKN020 - “broken layer of smoke aloft, based at two thousand”

                                  EXAMPLE- CIG 005V010 - “ceiling variable between five hundred and one thousand” EXAMPLE- CIG 020 RY11 - “ceiling two thousand at runway one one”

                                  EXAMPLE- SCT V BKN - “scattered layer variable to broken”
                                  BKN025 V OVC - “broken layer at two thousand five hundred variable to overcast”

                                    Cumulonimbus (CB), or Cumulonimbus Mammatus (CBMAM), distance (if known), direction from the station, and direction of movement, if known. If the clouds are beyond 10 miles from the airport, DSNT will indicate distance.

                                  EXAMPLE- CB W MOV E - “cumulonimbus west moving east”
                                  CBMAM DSNT S - “cumulonimbus mammatus distant south”

                                  EXAMPLE- TCU OHD - “towering cumulus overhead”
                                  TCU W - “towering cumulus west”

                                  EXAMPLE- ACC W - “altocumulus castellanus west”
                                  ACSL SW-S - “standing lenticular altocumulus southwest through south”
                                  APRNT ROTOR CLD S - “apparent rotor cloud south”
                                  CCSL OVR MT E - “standing lenticular cirrocumulus over the mountains east”

                                  EXAMPLE- 15/08 - “temperature one five, dew point 8”
                                  00/M02 - “temperature zero, dew point minus 2”
                                  M05/ - “temperature minus five, dew point missing”

                                  EXAMPLE- A2995 - “Altimeter two niner niner five”
                                  1. There are two categories of remarks:
                                    1. Automated, manual, and plain language.
                                    2. Additive and automated maintenance data.
                                    EXAMPLE- LTG DSNT W or LTG DSNT ALQDS

                                    Examples of METAR reports and explanation: METAR KBNA 281250Z 33018KT 290V360 1/2SM R31/2700FT SN BLSN FG VV008 00/M03 A2991 RMK RAE42 SN B42

                                    METAR aviation routine weather report
                                    KBNA Nashville, TN
                                    281250Z date 28 th , time 1250 UTC
                                    (no modifier) This is a manually generated report, due to the absence of “AUTO” and “AO1 or AO2” in remarks
                                    33018KT wind three three zero at one eight
                                    290V360 wind variable between two nine zero and three six zero
                                    1/2SM visibility one half
                                    R31/2700FT Runway three one RVR two thousand seven hundred
                                    SN moderate snow
                                    BLSN FG visibility obscured by blowing snow and fog
                                    VV008 indefinite ceiling eight hundred
                                    00/M03 temperature zero, dew point minus three
                                    A2991 altimeter two niner niner one
                                    RMK remarks
                                    RAE42 rain ended at four two
                                    SNB42 snow began at four two
                                    METAR KSFO 041453Z AUTO VRB02KT 3SM BR CLR 15/12 A3012 RMK AO2
                                    METAR aviation routine weather report
                                    KSFO San Francisco, CA
                                    041453Z date 4 th , time 1453 UTC
                                    AUTO fully automated; no human intervention
                                    VRB02KT wind variable at two
                                    3SM visibility three
                                    BR visibility obscured by mist
                                    CLR no clouds below one two thousand
                                    15/12 temperature one five, dew point one two
                                    A3012 altimeter three zero one two
                                    RMK remarks
                                    AO2 this automated station has a weather discriminator (for precipitation)

                                    NOTE- The “/” above and in the following descriptions are for separation purposes in this publication and do not appear in the actual TAFs.

                                    1. Type of Report. There are two types of TAF issuances, a routine forecast issuance (TAF) and an amended forecast (TAF AMD). An amended TAF is issued when the current TAF no longer adequately describes the on‐going weather or the forecaster feels the TAF is not representative of the current or expected weather. Corrected (COR) or delayed (RTD) TAFs are identified only in the communications header which precedes the actual forecasts.
                                    2. ICAO Station Identifier. The TAF code uses ICAO 4-letter location identifiers as described in the METAR section.
                                    3. Date and Time of Origin. This element is the date and time the forecast is actually prepared. The format is a two-digit date and four-digit time followed, without a space, by the letter “Z.”
                                    4. Valid Period Date and Time. The UTC valid period of the forecast consists of two four-digit sets, separated by a “/”. The first four-digit set is a two-digit date followed by the two-digit beginning hour, and the second four-digit set is a two-digit date followed by the two-digit ending hour. Although most airports have a 24-hour TAF, a select number of airports have a 30-hour TAF. In the case of an amended forecast, or a forecast which is corrected or delayed, the valid period may be for less than 24 hours. Where an airport or terminal operates on a part-time basis (less than 24 hours/day), the TAFs issued for those locations will have the abbreviated statement “AMD NOT SKED” added to the end of the forecasts. The time observations are scheduled to end and/or resume will be indicated by expanding the AMD NOT SKED statement. Expanded statements will include:
                                      1. Observation ending time (AFT DDHHmm; for example, AFT 120200)
                                      2. Scheduled observations resumption time (TIL DDHHmm; for example, TIL 171200Z) or
                                      3. Period of observation unavailability (DDHH/DDHH); for example, 2502/2512).

                                      EXAMPLE- 18010KT - wind one eight zero at one zero (wind is blowing from 180).
                                      35012G20KT - wind three five zero at one two gust two zero.

                                      EXAMPLE- 1 /2SM - visibility one-half
                                      4SM - visibility four
                                      P6SM - visibility more than six

                                      NOTE- It is very important that pilots understand that NSW only refers to weather phenomena, i.e., rain, snow, drizzle, etc. Omitted conditions, such as sky conditions, visibility, winds, etc., are carried over from the previous time group.

                                      NOTE- As in METAR, ceiling layers are not designated in the TAF code. For aviation purposes, the ceiling is the lowest broken or overcast layer or vertical visibility into a complete obscuration.

                                      SKC “sky clear”
                                      SCT005 BKN025CB “five hundred scattered, ceiling two thousand five hundred broken cumulonimbus clouds”
                                      VV008 “indefinite ceiling eight hundred”

                                      NOTE- NWS does not use PROB 40 in the TAF. However U.S. Military generated TAFS may include PROB40. PROB30 will not be shown during the first nine hours of a NWS forecast.

                                      EXAMPLE-
                                      PROB40 2221/2302 1 /2SM +TSRA “chance between 2100Z and 0200Z of visibility one-half statute mile in thunderstorms and heavy rain.”
                                      PROB30 3010/3014 1SM RASN “chance between 1000Z and 1400Z of visibility one statute mile in mixed rain and snow.”
                                        From (FM) group. The FM group is used when a rapid change, usually occurring in less than one hour, in prevailing conditions is expected. Typically, a rapid change of prevailing conditions to more or less a completely new set of prevailing conditions is associated with a synoptic feature passing through the terminal area (cold or warm frontal passage). Appended to the “FM” indicator is the six-digit date, hour, and minute the change is expected to begin and continues until the next change group or until the end of the current forecast. A “FM” group will mark the beginning of a new line in a TAF report (indented 5 spaces). Each “FM” group contains all the required elements-wind, visibility, weather, and sky condition. Weather will be omitted in “FM” groups when it is not significant to aviation. FM groups will not include the contraction NSW.

                                      EXAMPLE- FM210100 14010KT P6SM SKC - “after 0100Z on the 21st, wind one four zero at one zero, visibility more than six, sky clear.”

                                      NOTE- The NWS does not use BECMG in the TAF.

                                      EXAMPLE- OVC012 BECMG 0114/0116 BKN020 - “ceiling one thousand two hundred overcast. Then a gradual change to ceiling two thousand broken between 1400Z on the 1st and 1600Z on the 1st.”

                                      1. SCT030 TEMPO 0519/0523 BKN030 - “three thousand scattered with occasional ceilings three thousand broken between 1900Z on the 5th and 2300Z on the 5th.”
                                      2. 4SM HZ TEMPO 1900/1906 2SM BR HZ - “visibility four in haze with occasional visibility two in mist and haze between 0000Z on the 19th and 0600Z on the 19th.”
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