AIP航行情报汇编

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30 AUG 07 AIP United States of America GEN 3.5-17 15 MAR 07 Federal Aviation Administration Nineteenth Edition c) These SIGMETs are considered “widespread” because they must be either affecting or be forecasted to affect an area of at least 3,000 square miles at any one time. The International SIGMET is issued for 12_hours for volcanic ash events, 6 hours for hurricanes and tropical storms, and 4 hours for all other events. Like the domestic SIGMETs, Interna- tional SIGMETs are also identified by an alphabetic designator from Alpha through Mike and are numbered sequentially until that weather phenome- non ends. The criteria for an International SIGMET are: 1) Thunderstorms occurring in lines, embedded in clouds, or in large areas producing tornadoes or large hail. 2) Tropical cyclones. 3) Severe icing. 4) Severe or extreme turbulence. 5) Dust storms and sandstorms lowering visibilities to less than 3 miles. 6) Volcanic ash. EXAMPLE- Example of an International SIGMET: WSNT06 KKCI 022014 SIGA0F KZMA KZNY TJZS SIGMET FOXTROT 3 VALID 022015/030015 KKCI- MIAMI OCEANIC FIR NEW YORK OCEANIC FIR SAN JUAN FIR FRQ TS WI AREA BOUNDED BY 2711N6807W 2156N6654W 2220N7040W 2602N7208W 2711N6807W. TOPS TO FL470. MOV NE 15KT. WKN. BASED ON SAT AND LTG OBS. MOSHER 3.9.3.6 AIRMET (WA) a) AIRMETs (WAs) are advisories of significant weather phenomena but describe conditions at intensities lower than those which require the issuance of SIGMETs. AIRMETs are intended for dissemination to all pilots in the preflight and en route phase of flight to enhance safety. AIRMET Bulletins are issued on a scheduled basis every 6 hours beginning at 0145 UTC during Central Daylight Time and at 0245 UTC during Central Standard Time. Unscheduled updates and corrections are issued as necessary. Each AIRMET Bulletin contains any current AIRMETs in effect and an outlook for conditions expected after the AIRMET valid period. AIRMETs contain details about IFR, extensive mountain obscuration, turbulence, strong surface winds, icing, and freezing levels. b) There are three AIRMETs: Sierra, Tango, and Zulu. After the first issuance each day, scheduled or unscheduled bulletins are numbered sequentially for easier identification. 1) AIRMET Sierra describes IFR conditions and/or extensive mountain obscurations. 2) AIRMET Tango describes moderate turbu- lence, sustained surface winds of 30 knots or greater, and/or nonconvective low-level wind shear. 3) AIRMET Zulu describes moderate icing and provides freezing level heights.

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EXAMPLE- Example of AIRMET Sierra issued for the Chicago FA area: CHIS WA 121345 AIRMET SIERRA UPDT 3 FOR IFR AND MTN OBSCN VALID UNTIL 122000. AIRMET IFR...SD NE MN IA MO WI LM MI IL IN KY FROM 70NW RAP TO 50W RWF TO 50W MSN TO GRB TO MBS TO FWA TO CVG TO HNN TO TRI TO ARG TO 40SSW BRL TO OMA TO BFF TO 70NW RAP OCNL CIG BLW 010/VIS BLW 3SM FG/BR. CONDS ENDG 15Z-17Z. AIRMET MTN OBSCN...KY TN FROM HNN TO TRI TO CHA TO LOZ TO HNN MTNS OCNL OBSC CLDS/PCPN/BR. CONDS ENDG TN PTN AREA 18Z- 20Z..CONTG KY BYD 20Z..ENDG 02Z. EXAMPLE- Example of AIRMET Tango issued for the Salt Lake City FA area: SLCT WA 121345 AIRMET TANGO UPDT 2 FOR TURB VALID UNTIL 122000. AIRMET TURB...NV UT CO AZ NM FROM LKV TO CHE TO ELP TO 60S TUS TO YUM TO EED TO RNO TO LKV OCNL MOD TURB BLW FL180 DUE TO MOD SWLY/WLY WNDS. CONDS CONTG BYD 20Z THRU 02Z. AIRMET TURB...NV WA OR CA CSTL WTRS FROM BLI TO REO TO BTY TO DAG TO SBA TO 120W FOT TO 120W TOU TO BLI OCNL MOD TURB BTWN FL180 AND FL400 DUE TO WNDSHR ASSOCD WITH JTSTR. CONDS CONTG BYD 20Z THRU 02Z. 30 AUG 07 AIP United States of America GEN 3.5-18 15 MAR 07 Federal Aviation Administration Nineteenth Edition EXAMPLE- Example of AIRMET Zulu issued for the San Francisco FA area: SFOZ WA 121345 AIRMET ZULU UPDT 2 FOR ICE AND FRZLVL VALID UNTIL 122000. AIRMET ICE...WA OR ID MT NV UT FROM YQL TO SLC TO WMC TO LKV TO PDT TO YDC TO YQL LGT OCNL MOD RIME/MXD ICGICIP BTWN FRZLVL AND FL220. FRZLVL 080-120. CONDS CONTG BYD 20Z THRU 02Z. AIRMET ICE...WA OR FROM YDC TO PDT TO LKV TO 80W MFR TO ONP TO TOU TO YDC LGT OCNL MOD RIME/MXD ICGICIP BTWN FRZLVL AND FL180. FRZLVL 060-080. CONDS CONTG BYD 20Z THRU 02Z. FRZLVL...WA...060 CSTLN SLPG 100 XTRM E. OR...060-070 CASCDS WWD. 070-095 RMNDR. NRN CA...060-100 N OF A 30N FOT-40N RNO LN SLPG 100-110 RMNDR. 3.9.3.7 Severe Weather Watch Bulletins (WWs) and Alert Messages (AWWs) a) WWs define areas of possible severe thunder- storms or tornado activity. The bulletins are issued by the Storm Prediction Center (SPC) in Norman, OK. WWs are unscheduled and are issued as required. b) A severe thunderstorm watch describes areas of expected severe thunderstorms. (Severe thunder- storm criteria are 3 /4-inch hail or larger and/or wind gusts of 50 knots [58 mph] or greater.) c) A tornado watch describes areas where the threat of tornadoes exists. d) In order to alert the WFOs, CWSUs, FSSs, and other users, a preliminary notification of a watch called the Alert Severe Weather Watch bulletin (AWW) is sent before the WW. (WFOs know this product as a SAW).

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EXAMPLE- Example of an AWW: MKC AWW 011734 WW 75 TORNADO TX OK AR 011800Z-020000Z AXIS..80 STATUTE MILES EAST AND WEST OF A LINE..60ESE DAL/DALLAS TX/ - 30 NW ARG/ WALNUT RIDGE AR/ ..AVIATION COORDS.. 70NM E/W /58W GGG - 25NW ARG/ HAIL SURFACE AND ALOFT..1 3 /4 INCHES. WIND GUSTS..70 KNOTS. MAX TOPS TO 450. MEAN WIND VECTOR 24045. e) Soon after the AWW goes out, the actual watch bulletin itself is issued. A WW is in the following format: 1) Type of severe weather watch, watch area, valid time period, type of severe weather possible, watch axis, meaning of a watch, and a statement that persons should be on the lookout for severe weather. 2) Other watch information; i.e., references to previous watches. 3) Phenomena, intensities, hail size, wind speed (knots), maximum cumulonimbus (CB) tops, and estimated cell movement (mean wind vector). 4) Cause of severe weather. 5) Information on updating Convective Outlook (AC) products. EXAMPLE- Example of a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nited States of America GEN 3.5-19 15 MAR 07 Federal Aviation Administration Nineteenth Edition MID LVL FLOW INDICATE A THREAT FOR SUPER- CELLS. AVIATION...TORNADOES AND A FEW SEVERE THUN- DERSTORMS WITH HAIL SURFACE AND ALOFT TO 2_3 /4 INCHES. EXTREME TURBULENCE AND SUR- FACE WIND GUSTS TO 70 KNOTS. A FEW CUMULO- NIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM MOTION VECTOR 28025. f) Status reports are issued as needed to show progress of storms and to delineate areas no longer under the threat of severe storm activity. Cancellation bulletins are issued when it becomes evident that no severe weather will develop or that storms have subsided and are no longer severe. g) When tornadoes or severe thunderstorms have developed, the local WFO office will issue the warnings covering those areas. 3.9.3.8 Center Weather Advisories (CWAs) a) CWAs 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. CWAs 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 condi- tions. 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. b) The following example is a CWA issued from the Kansas City, Missouri, ARTCC. The “3” after ZKC in the first line denotes this CWA has been issued for the third weather phenomena to occur for the day. The “301” in the second line denotes the phenomena number again (3) and the issuance number (01) for this phenomena. The CWA was issued at 2140Z and is valid until 2340Z. EXAMPLE- ZKC3 CWA 032140 ZKC CWA 301 VALID UNTIL 032340 ISOLD SVR TSTM over KCOU MOVG SWWD 10 KTS ETC. 4. Categorical Outlooks 4.1 Categorical outlook terms describing general ceiling and visibility conditions for advance planning purposes are used only in area forecasts. They are defined as follows: 4.1.1 LIFR (Low IFR)_-_Ceiling less than 500 feet and/or visibility less than 1 mile. 4.1.2 IFR_-_Ceiling 500 to less than 1,000 feet and/or visibility 1 to less than 3 miles. 4.1.3 MVFR (Marginal VFR)_-_Ceiling 1,000 or 3,000 feet and/or visibility 3 to 5 miles inclusive. 4.1.4 VFR_-_Ceiling greater than 3,000 feet and visibility greater than 5 miles; includes sky clear. 4.2 The cause of LIFR, IFR, or MVFR is indicated by either ceiling or visibility restrictions or both. The contraction “CIG” and/or weather and obstruction to vision symbols are used. If winds or gusts of 25 knots or greater are forecast for the outlook period, the word “WIND” is also included for all categories, including VFR. EXAMPLE- LIFR CIG-low IFR due to low ceiling. IFR FG-IFR due to visibility restricted by fog. MVFR CIG HZ FU-marginal VFR due both to ceiling and to visibility restricted by haze and smoke. IFR CIG RA WIND-IFR due both to low ceiling and to visibility restricted by rain; wind expected to be 25 knots or greater. 30 AUG 07 AIP United States of America GEN 3.5-20 15 MAR 07 Federal Aviation Administration Nineteenth Edition 5. Telephone Information Briefing Service (TIBS)_ 5.1 TIBS, provided by automated flight service stations (AFSSs), is a continuous recording of meteorological and aeronautical information, avail- able by telephone. Each AFSS provides at least four route and/or area briefings. In addition, airspace procedures and special announcements (if applica- ble) concerning aviation interests are also available. Depending upon user demand, other items may be provided; i.e., METAR observations, terminal airport forecasts, winds aloft, and temperatures aloft forecasts. 6. Inflight Weather Broadcasts 6.1 Weather Advisory Broadcasts. ARTCCs' broadcast a Severe Weather Forecast Alert (AWW), Convective SIGMET, or CWA alert once on all frequencies, except emergency, when any part of the area described is within 150 miles of the airspace under their jurisdiction. These broadcasts contain SIGMET or CWA identification and a brief description of the weather activity and general area affected. EXAMPLE- 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. EXAMPLE- 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. EXAMPLE- 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. NOTE- Terminal control facilities have the option to limit the AWW, Convective SIGMET, SIGMET, or CWA broadcast as follows: local control and approach control positions may opt to broadcast SIGMET or CWA alerts only when any part of the area described is within 50 miles of the airspace under their jurisdiction. 6.2 Hazardous Inflight Weather Advisory Ser- vice (HIWAS). This is a continuous broadcast of inflight weather advisories including summarized AWWs, SIGMETs, Convective SIGMETs, CWAs, AIRMETs, and urgent PIREPs. HIWAS has been adopted as a national program and will be implemented throughout the conterminous U.S. as resources permit. In those areas where HIWAS is commissioned, ARTCC, Terminal ATC, and AFSS/ FSS facilities have discontinued the broadcast of inflight advisories. HIWAS is an additional source of hazardous weather information which makes these data available on a continuous basis. It is not, however, a replacement for preflight or inflight briefings or real-time weather updates from Flight Watch (EFAS). As HIWAS is implemented in individual center areas, the commissioning will be advertised in the Notices to Airmen publication. 6.2.1 Where HIWAS has been implemented, a HIWAS alert will be broadcast on all except emergency frequencies once upon receipt by ARTCC and terminal facilities which will include an alert announcement, frequency instruction, number, and type of advisory updated; e.g., AWW, SIGMET, Convective SIGMET, or CWA. EXAMPLE- Attention all aircraft. Hazardous weather information (SIGMET, Convective SIGMET, AIRMET, urgent pilot weather report (UUA), or Center Weather Advisory (CWA)), (number or numbers) for (geographical area) available on HIWAS, flight watch, or flight service frequencies. 6.2.2 In HIWAS ARTCC areas, AFSSs/FSSs will broadcast a HIWAS update announcement once on all except emergency frequencies upon completion of recording an update to the HIWAS broadcast. Included in the broadcast will be the type of advisory update; e.g., AWW, SIGMET, Convective SIGMET, or CWA. EXAMPLE- Attention all aircraft. Hazardous weather information for (geographical area) available from flight watch or flight service. 6.2.3 HIWAS availability is shown on IFR En Route Low Altitude Charts and VFR Sectional Charts. The symbol depiction is identified in the chart legend. 30 AUG 07 AIP United States of America GEN 3.5-21 15 MAR 07 Federal Aviation Administration Nineteenth Edition 7. Flight Information Services (FIS) 7.1 FIS. Aviation weather and other operational information may be displayed in the cockpit through the use of FIS. FIS systems are of two basic types: Broadcast only systems (called FIS-B) and two-way request/reply systems. Broadcast system components include a ground- or space-based transmitter, an aircraft receiver, and a portable or installed cockpit display device. Two-way systems utilize transmitter/ receivers at both the ground- or space-based site and the aircraft. 7.1.1 Broadcast FIS (i.e., FIS-B) allows the pilot to passively collect weather and other operational data and to display that data at the appropriate time. In addition to textual weather products such as Aviation Routine Weather Reports (METARs)/Aviation Se- lected Special Weather Reports (SPECIs) and Terminal Area Forecasts (TAFs), graphical weather products such as radar composite/mosaic images, temporary flight restricted airspace and other NOTAMs may be provided to the cockpit. Two-way FIS services permit the pilot to make specific weather and other operational information requests for cockpit display. A FIS service provider will then prepare a reply in response to that specific request and transmit the product to that specific aircraft. 7.1.2 FIS services are available from four types of service providers: 7.1.2.1 A private sector FIS provider operating under service agreement with the FAA using broadcast data link over VHF aeronautical spectrum and whose products have been reviewed and accepted by the FAA prior to transmission. (Products and services are defined under subparagraph 7.3.) 7.1.2.2 Through an FAA operated service using a broadcast data link on the ADS-B UAT network. (Products and services are defined under subpara- graph 7.4.) 7.1.2.3 Private sector FIS providers operating under customer contracts using aeronautical spectrum. 7.1.2.4 Private sector FIS providers operating under customer contract using methods other than aeronautical spectrum, including Internet data-tothe-cockpit service providers. 7.1.3 FIS is a method of receiving aviation weather and other operational data in the cockpit that augments traditional pilot voice communication with FAA's Flight Service Stations (FSSs), ATC facilities, or Airline Operations Control Centers (AOCCs). FIS is not intended to replace traditional pilot and controller/flight service specialist/aircraft dispatcher pre-flight briefings or inflight voice communica- tions. FIS; however, can provide textual and graphical background information that can help abbreviate and improve the usefulness of such communications. FIS enhances pilot situational awareness and improves safety. 7.1.4 To ensure airman compliance with Federal Aviation Regulations, manufacturer's operating manuals should remind airmen to contact ATC controllers, FSS specialists, operator dispatchers, or airline operations control centers for general and mission critical aviation weather information and/or NAS status conditions (such as NOTAMs, Special Use Airspace status, and other government flight information). If FIS products are systemically modified (for example, are displayed as abbreviated plain text and/or graphical depictions), the modifica- tion process and limitations of the resultant product should be clearly described in the vendor's user guidance. 7.2 Operational Use of FIS. Regardless of the type of FIS system being used, several factors must be considered when using FIS: 7.2.1 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. 7.2.2 FIS should not serve as the sole source of aviation weather and other operational information. ATC, AFSSs and, if applicable, AOCC VHF/HF voice remain as a redundant method of communicat- ing aviation weather, NOTAMs, and other operation- al 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 30 AUG 07 AIP United States of America GEN 3.5-22 15 MAR 07 Federal Aviation Administration Nineteenth Edition 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. 7.2.3 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. 7.2.4 FIS aviation weather products (e.g., graphical ground-based radar precipitation depictions) are not appropriate for tactical avoidance of severe weather such as negotiating a path through a weather hazard area. FIS supports strategic 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 pre-flight weather and flight planning briefing. 7.2.5 FIS NOTAM products, including Temporary Flight Restriction (TFR) information, are advisoryuse information and are intended for situational awareness purposes only. Cockpit displays of this information are not appropriate for tactical naviga- tion - pilots should stay clear of any geographic area displayed as a TFR NOTAM. Pilots should contact FSSs and/or ATC while en route to obtain updated information and to verify the cockpit display of NOTAM information. 7.2.6 FIS supports better pilot decision making by increasing situational awareness. Better decisionmaking 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, FAA's en route “Flight Watch” service, data from other air traffic control facilities, airline operation control centers, pilot reports, as well as their own observations. 7.3 FAA FISDL (VHF) Service. The FAA's FISDL (VHF datalink) system is a VHF Data Link (VDL) Mode 2 implementation that provides pilots and flight crews of properly equipped aircraft with a cockpit display of certain aviation weather and flight operational information. This information may be displayed in both textual and graphical formats. The system is operated under a service agreement with the FAA, using broadcast data link on VHF aeronautical spectrum on two 25 KHz spaced frequencies (136.450 and 136.475 MHz). The FAA FISDL (VHF) service is designed to provide coverage throughout the continental U.S. from 5,000 feet AGL to 17,500 feet MSL, except in areas where this is not feasible due to mountainous terrain. Aircraft operating near transmitter sites may receive useable FISDL signals at altitudes lower than 5,000 feet AGL, including on the surface in some locations, depending on transmitter/aircraft line of sight geometry. Aircraft operating above 17,500 feet MSL may also receive useable FISDL signals under certain circumstances. 7.3.1 FAA FISDL (VHF) service provides, free of charge, the following basic text products: 7.3.1.1 Aviation Routine Weather Reports (METARs). 7.3.1.2 Aviation Selected Special Weather Reports (SPECIs). 7.3.1.3 Terminal Area Forecasts (TAFs), and their amendments. 7.3.1.4 Significant Meteorological Information (SIGMETs). 7.3.1.5 Convective SIGMETs. 7.3.1.6 Airman's Meteorological Information (AIRMETs). 7.3.1.7 Pilot Reports (both urgent and routine) (PIREPs); and, 7.3.1.8 Severe Weather Forecast Alerts and Warn- ings (AWWs/WW) issued by the NOAA Storm Prediction Center (SPC). 7.3.2 The format and coding of these text products are described in Advisory Circular AC-00-45, Aviation Weather Services, and FIG GEN 3.5-23 and FIG GEN 3.5-24, Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR). 7.3.3 Additional products, called “Value-Added Products,” are also available from the vendor on a paid subscription basis. Details concerning the 30 AUG 07 AIP United States of America GEN 3.5-23 15 MAR 07 Federal Aviation Administration Nineteenth Edition content, format, symbology and cost of these products may be obtained from the vendor. 7.4 FAA's Flight Information Service-Broadcast (FIS-B) Service. FIS-B is a ground broadcast service provided through the FAA's Universal Access Transceiver (UAT) “ADS-B Broadcast Services” network. The UAT network is an ADS-B data link that operates on 978 MHz. The FAA FIS-B system provides pilots and flight crews of properly equipped aircraft with a cockpit display of certain aviation weather and flight operational information. The FAA's FIS-B service is being introduced in certain regional implementations within the NAS (e.g., in Alaska and in other areas of implementation). 7.4.1 FAA's UAT FIS-B provides the initial products listed below with additional products planned for future implementation. FIS-B reception is line of sight and can be expected within 200 NM (nominal range) of each ground transmitting site. The following services are provided free of charge. 7.4.1.1 Text: Aviation Routine Weather Reports (METARs). 7.4.1.2 Text: Special Aviation Reports (SPECIs). 7.4.1.3 Text: Terminal Area Forecasts (TAFs), and their amendments. 7.4.1.4 Graphic: NEXRAD precipitation maps. 7.4.2 The format and coding of the above text weather-related products are described in Advisory Circular AC-00-45, Aviation Weather Services, and FIG GEN 3.5-23 and FIG GEN 3.5-24, Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR). 7.4.3 Details concerning the content, format, and symbology of the various data link products provided may be obtained from the specific avionics manufacturer. 7.5 Non-FAA FISDL Systems. Several commer- cial vendors also provide customers with FIS data over both the aeronautical spectrum and on other frequencies using a variety of data link protocols. In some cases, the vendors provide only the commu- nications system that carries customer messages, such as the Aircraft Communications Addressing and Reporting System (ACARS) used by many air carrier and other operators. 7.5.1 Operators using non-FAA FIS data for inflight weather and other operational information should ensure that the products used conform to FAA/NWS standards. Specifically, aviation weather and NAS status information should meet the following criteria: 7.5.1.1 The products should be either FAA/NWS “accepted” aviation weather reports or products, or based on FAA/NWS accepted aviation weather reports or products. If products are used which do not meet this criteria, they should be so identified. The operator must determine the applicability of such products to their particular flight operations. 7.5.1.2 In the case of a weather product which is the result of the application of a process which alters the form, function or content of the base FAA/NWS accepted weather product(s), that process, and any limitations to the application of the resultant product, should be described in the vendor's user guidance material. 7.5.2 An example would be a NEXRAD radar composite/mosaic map, which has been modified by changing the scaling resolution. The methodology of assigning reflectivity values to the resultant image components should be described in the vendor's guidance material to ensure that the user can accurately interpret the displayed data. 8. Weather Observing Programs 8.1 Manual Observations. Aviation Routine Weather Reports (METAR) are taken at more than 600 locations in the U.S. With only a few exceptions, these stations are located at airport sites and most are staffed by FAA or NWS personnel who manually observe, perform calculations, and enter the observation into the distribution system. The format and coding of these observations are contained in FIG GEN 3.5-23. 8.2 Automated Weather Observing System (AWOS) 8.2.1 Automated weather reporting systems are increasingly being installed at airports. These systems consist of various sensors, a processor, a computer-generated voice subsystem, and a trans- mitter to broadcast local, minute-by-minute weather data directly to the pilot. NOTE- When the barometric pressure exceeds 31.00 inches Hg., see Section ENR 1.7, Altimeter Setting Procedures. 8.2.2 The AWOS observations will include the prefix “AUTO” to indicate that the data are derived 30 AUG 07 AIP United States of America GEN 3.5-24 15 MAR 07 Federal Aviation Administration Nineteenth Edition from an automated system. Some AWOS locations will be augmented by certified observers who will provide weather and obstruction to vision informa- tion in the remarks of the report when the reported visibility is less than 3 miles. These sites, along with the hours of augmentation, are published in the Airport/Facility Directory. Augmentation is identi- fied in the observation as “OBSERVER WEATH- ER.” The AWOS wind speed, direction and gusts, temperature, dew point, and altimeter setting are exactly the same as for manual observations. The AWOS will also report density altitude when it exceeds the field elevation by more than 1,000 feet. The reported visibility is derived from a sensor near the touchdown of the primary instrument runway. The visibility sensor output is converted to a visibility value using a 10-minute harmonic average. The reported sky condition/ceiling is derived from the ceilometer located next to the visibility sensor. The AWOS algorithm integrates the last 30 minutes of ceilometer data to derive cloud layers and heights. This output may also differ from the observer sky condition in that the AWOS is totally dependent upon the cloud advection over the sensor site. 8.2.3 Referred to as AWOS, these real-time systems are operationally classified into four basic levels: 8.2.3.1 AWOS-A: only reports altimeter setting. NOTE- Any other information is advisory only. 8.2.3.2 AWOS-l: usually reports altimeter setting, wind data, temperature, dew point, and density altitude. 8.2.3.3 AWOS-2 provides the information provided by AWOS-l, plus visibility. 8.2.3.4 AWOS-3 provides the information provided by AWOS-2, plus cloud/ceiling data. 8.2.4 The information is transmitted over a discrete VHF radio frequency or the voice portion of a local NAVAID. AWOS transmissions on a discrete VHF radio frequency are engineered to be receivable to a maximum of 25 NM from the AWOS site and a maximum altitude of 10,000 feet AGL. At many locations, AWOS signals may be received on the surface of the airport, but local conditions may limit the maximum AWOS reception distance and/or altitude. The system transmits a 20- to 30-second weather message updated each minute. Pilots should monitor the designated frequency for the automated weather broadcast. A description of the broadcast is contained in paragraph 8.3, Automated Weather Observing System (AWOS) Broadcasts. There is no two-way communication capability. Most AWOS sites also have a dial-up capability so that the minute-by-minute weather messages can be ac- cessed via telephone. 8.2.5 AWOS information (system level, frequency, phone number) concerning specific locations is published, as the systems become operational, in the Airport/Facility Directory and, where applicable, on published Instrument Approach Procedure (IAP) charts. Selected individual systems may be incorpo- rated into nationwide data collection and dissemina- tion networks in the future. 8.3 Automated Weather Observing System (AWOS) Broadcasts. Computer-generated voice is used in AWOS to automate the broadcast of the minute-by-minute weather observations. In addi- tion, some systems are configured to permit the addition of an operator-generated voice message; e.g., weather remarks, following the automated parameters. The phraseology used generally follows that used for other weather broadcasts. Following are explanations and examples of the exceptions. 8.3.1 Location and Time. The location/name and the phrase “AUTOMATED WEATHER OBSERVA- TION” followed by the time are announced. 8.3.1.1 If the airport's specific location is included in the airport's name, the airport's name is announced. EXAMPLE- “Bremerton National Airport automated weather observation one four five six zulu.” “Ravenswood Jackson County Airport automated weather observation one four five six zulu.” 8.3.1.2 If the airport's specific location is not included in the airport's name, the location is announced followed by the airport's name. EXAMPLE- “Sault Ste. Marie, Chippewa County International Airport automated weather observation.” “Sandusky, Cowley Field automated weather observation.”

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8.3.1.3 The word “TEST” is added following “OBSERVATION” when the system is not in commissioned status. 30 AUG 07 AIP United States of America GEN 3.5-25 15 MAR 07 Federal Aviation Administration Nineteenth Edition EXAMPLE- “Bremerton National Airport automated weather observation test one four five six zulu.” 8.3.1.4 The phrase “TEMPORARILY INOPERA- TIVE” is added when the system is inoperative. EXAMPLE- “Bremerton National Airport automated weather observing system temporarily inoperative.” 8.3.2 Ceiling and Sky Cover 8.3.2.1 Ceiling is announced as either “CEILING” or “INDEFINITE CEILING.” The phrases “MEA- SURED CEILING” and “ESTIMATED CEILING” are not used. With the exception of indefinite ceilings, all automated ceiling heights are measured. 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.” 8.3.2.2 The word “CLEAR” is not used in AWOS due to limitations in the height ranges of the sensors. No clouds detected is announced as, “No clouds below XXX” or, in newer systems as, “Clear below XXX” (where XXX is the range limit of the sensor). EXAMPLE- “No clouds below one two thousand.” “Clear below one two thousand.” 8.3.2.3 A sensor for determining ceiling and sky cover is not included in some AWOS. In these systems, ceiling and sky cover are not announced. “SKY CONDITION MISSING” is announced only if the system is configured with a ceilometer, and the ceiling and sky cover information is not available. 8.3.3 Visibility 8.3.3.1 The lowest reportable visibility value in AWOS is “less than 1 /4.” It is announced as “VISIBILITY LESS THAN ONE QUARTER.” 8.3.3.2 A sensor for determining visibility is not included in some AWOSs. 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. 8.3.4 Weather. In the future, some AWOSs are to be configured to determine the occurrence of precipitation. However, the type and intensity may not always be determined. In these systems, the word “PRECIPITATION” will be announced if precipita- tion is occurring, but the type and intensity are not determined. 8.3.5 Remarks. If remarks are included in the observation, the word “REMARKS” is announced following the altimeter setting. Remarks are announced in the following order of priority: 8.3.5.1 Automated “remarks.” a) Variable visibility. b) Density altitude. 8.3.5.2 Manual input remarks. Manual input remarks are prefaced with the phrase “OBSERVER WEATHER.” As a general rule the manual remarks are limited to: a) Type and intensity of precipitation. b) __Thunderstorms, intensity (if applicable), and direction. c) Obstructions to vision when the visibility is less than 7 miles. 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 mist...thunderstorm overhead.” 8.3.5.3 If an automated parameter is “missing” and no manual input for that parameter is available, the parameter is announced as “MISSING.” For example, a report with the dew point “missing,” and no manual input available, would be announced as follows: EXAMPLE- “Ceiling one thousand overcast, visibility three, precipita- tion, temperature three zero, dew point missing, wind calm, altimeter three zero zero one.” 8.3.5.4 “REMARKS” are announced in the follow- ing order of priority: a) Automated “REMARKS”: 1) Variable visibility. 2) Density altitude. b) Manual Input “REMARKS.” As a general rule, the remarks are announced in the same order as the parameters appear in the basic text of the observation. 30 AUG 07 AIP United States of America GEN 3.5-26 15 MAR 07 Federal Aviation Administration Nineteenth Edition 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.” 8.4 Automated Surface Observing System (ASOS)/Automated Weather Sensor System (AWSS) 8.4.1 The ASOS/AWSS is the primary surface weather observing system of the U.S. The program to install and operate these systems throughout the U.S. is a joint effort of the NWS, the FAA and the Department of Defense. AWSS is a follow-on program that provides identical data as ASOS. ASOS/AWSS is designed to support aviation operations and weather forecast activities. The ASOS/AWSS will provide continuous minute-by- minute observations and perform the basic observing functions necessary to generate an aviation routine weather report (METAR) and other aviation weather information. The information may be transmitted over a discrete VHF radio frequency or the voice portion of a local NAVAID. ASOS/AWSS transmis- sions on a discrete VHF radio frequency are engineered to be receivable to a maximum of 25 NM from the ASOS/AWSS site and a maximum altitude of 10,000 feet AGL. At many locations, ASOS/ AWSS signals may be received on the surface of the airport, but local conditions may limit the maximum reception distance and/or altitude. While the automated system and the human may differ in their methods of data collection and interpretation, both produce an observation quite similar in form and content. For the “objective” elements such as pressure, ambient temperature, dew point tempera- ture, wind, and precipitation accumulation, both the automated system and the observer use a fixed location and time-averaging technique. The quantita- tive differences between the observer and the automated observation of these elements are negligible. For the “subjective” elements, however, observers use a fixed time, spatial averaging technique to describe the visual elements (sky condition, visibility and present weather), while the automated systems use a fixed location, time averaging technique. Although this is a fundamental change, the manual and automated techniques yield remarkably similar results within the limits of their respective capabilities. (See FIG GEN 3.5-25 and FIG GEN 3.5-26, Key to Decode an ASOS/AWSS (METAR) Observation. 8.4.2 System Description 8.4.2.1 The ASOS/AWSS at each airport location consists of four main components: a) Individual weather sensors. b) Data collection and processing units. c) Peripherals and displays. 8.4.2.2 The ASOS/AWSS sensors perform the basic function of data acquisition. They continuously sample and measure the ambient environment, derive raw sensor data and make them available to the collection and processing units. 8.4.3 Every ASOS/AWSS will contain the follow- ing basic set of sensors. 8.4.3.1 Cloud height indicator (one or possibly three). 8.4.3.2 Visibility sensor (one or possibly three). 8.4.3.3 Precipitation identification sensor. 8.4.3.4 Freezing rain sensor. 8.4.3.5 Pressure sensors (two sensors at small airports; three sensors at large airports). 8.4.3.6 Ambient temperature/dew point temperature sensor. 8.4.3.7 Anemometer (wind direction and speed sensor). 8.4.3.8 Rainfall accumulation sensor. 8.4.4 The ASOS/AWSS data outlets include: 8.4.4.1 Those necessary for on-site airport users. 8.4.4.2 National communications networks. 8.4.4.3 Computer-generated voice (available through FAA radio broadcast to pilots and dial-in telephone line). NOTE- Wind direction broadcast over FAA radios is in reference to magnetic north. 8.5 A comparison of weather observing programs and the elements observed by each are in TBL GEN 3.5-2, Weather Observing Programs. 8.6 Service Standards. During 1995, a govern- ment/industry team worked to comprehensively reassess the requirements for surface observations at 30 AUG 07 AIP United States of America GEN 3.5-27 15 MAR 07 Federal Aviation Administration Nineteenth Edition 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 the 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 GEN 3.5-3, Weather Observation Service Standards. 8.6.1 Service Level D defines the minimum acceptable level of service. It is a completely automated service in which the ASOS 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. 8.6.2 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 elements in the event of an ASOS malfunction or an unrepresentative ASOS report. 8.6.3 In backup, the human observer inserts the correct or missing value for the automated ASOS 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. 8.6.4 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. This category of airports includes smaller hubs or airports special in other ways that have worse than average bad weather operations for thunderstorms and/or freezing/frozen precipitation, and/or that are remote airports. 8.6.5 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. 30 AUG 07 AIP United States of America GEN 3.5-28 15 MAR 07 Federal Aviation Administration Nineteenth Edition TBL GEN 3.5-2 Weather Observing Programs Element Reported AWOS-A AWOS-1 AWOS-2 AWOS-3 ASOS MANUAL Altimeter X X X X X X Wind X X X X X Temperature/Dew point X X X X X Density altitude X X X X Visibility X X X X Clouds/Ceiling X X X Precipitation X X Remarks X X TBL GEN 3.5-3 Weather Observation Service Standards 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 continually measuring the atmosphere at a point near the runway. The ASOS senses and measures the weather parameters listed to the right. Wind Visibility Precipitation/Obstruction to vision Cloud height Sky cover Temperature Dew point Altimeter 30 AUG 07 AIP United States of America GEN 3.5-29 15 MAR 07 Federal Aviation Administration Nineteenth Edition 9. Weather Radar Services 9.1 The National Weather Service operates a network of radar sites for detecting coverage, intensity, and movement of precipitation. The network is supplemented by FAA and DOD radar sites in the western sections of the country. Local warning radars augment the network by operating on an as needed basis to support warning and forecast programs. 9.2 Scheduled radar observations are taken hourly and transmitted in alpha-numeric format on weather telecommunications circuits for flight planning purposes. Under certain conditions special radar reports are issued in addition to the hourly transmittals. Data contained in the reports is also collected by the National Meteorological Center and used to prepare hourly national radar summary charts for dissemination on facsimile circuits. 9.3 All En route Flight Advisory Service facilities and many Automated Flight Service Stations 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 the ARTCCs also have access to weather radar displays and provide support to all air traffic facilities within their center's area. 9.4 A clear radar display (no echoes) does not mean that there is no significant weather within the coverage of the radar site. Clouds and fog are not detected by the radar. However, when echoes are present, turbulence can be implied by the intensity of the precipitation, and icing is implied by the presence of the precipitation at temperatures at or below zero degrees Celsius. Used in conjunction with other weather products, radar provides invaluable informa- tion for weather avoidance and flight planning. 9.5 Additional information on weather radar prod- ucts and services can be found in FAA Advisory Circular 00-45, “Aviation Weather Services.” REFERENCE- Pilot/Controller Glossary Term- Precipitation Radar Weather Descriptions. AIP, Thunderstorms, GEN 3.5, Paragraph 27. Airport/Facility Directory, Charts, NWS Upper Air Observing Stations and Weather Network for the location of specific radar sites. 10. ATC Inflight Weather Avoidance Assistance 10.1 ATC Radar Weather Display 10.1.1 ATC radars are able to display areas of precipitation by sending out a beam of radio energy that is reflected back to the radar antenna when it strikes an object or moisture which may be in the form of rain drops, hail, or snow. The larger the object is, or the more dense its reflective surface, the stronger the return will be presented. Radar weather processors indicate the intensity of reflective returns in terms of decibels (dBZ). ATC systems cannot detect the presence or absence of clouds. The ATC systems can often determine the intensity of a precipitation area, but the specific character of that area (snow, rain, hail, VIRGA, etc.) cannot be determined. For this reason, ATC refers to all weather areas displayed on ATC radar scopes as “precipita- tion.” 10.1.2 All ATC facilities using radar weather processors with the ability to determine precipitation intensity, will describe the intensity to pilots as: 10.1.2.1 “LIGHT” (< 30 dBZ) 10.1.2.2 “MODERATE” (30 to 40 dBZ) 10.1.2.3 “HEAVY” (> 40 to 50 dBZ) 10.1.2.4 “EXTREME” (> 50 dBZ) 10.1.3 ATC facilities that, due to equipment limitations, cannot display the intensity levels of precipitation, will describe the location of the precipitation area by geographic position, or position relative to the aircraft. Since the intensity level is not available, the controller will state “INTENSITY UNKNOWN.” 10.1.4 ARTCC facilities normally use a Weather and Radar Processor (WARP) to display a mosaic of data obtained from multiple NEXRAD sites. There is a time delay between actual conditions and those displayed to the controller. For example, the precipitation data on the ARTCC controller's display could be up to 6 minutes old. When the WARP is not available, a second system, the narrowband Air Route Surveillance Radar (ARSR) can display two distinct levels of precipitation intensity that will be described to pilots as “MODERATE” (30 to 40 dBZ) and “HEAVY TO EXTREME” ( > 40 dBZ ). The WARP processor is only used in ARTCC facilities. 10.1.5 ATC radar is not able to detect turbulence. Generally, turbulence can be expected to occur as the 30 AUG 07 AIP United States of America GEN 3.5-30 15 MAR 07 Federal Aviation Administration Nineteenth Edition rate of rainfall or intensity of precipitation increases. Turbulence associated with greater rates of rainfall/ precipitation will normally be more severe than any associated with lesser rates of rainfall/precipitation. Turbulence should be expected to occur near convective activity, even in clear air. Thunderstorms are a form of convective activity that imply severe or greater turbulence. Operation within 20 miles of thunderstorms should be approached with great caution, as the severity of turbulence can be markedly greater than the precipitation intensity might indicate. 10.2 Weather Avoidance Assistance 10.2.1 To the extent possible, controllers will issue pertinent information of weather or chaff areas and assist pilots in avoiding such areas if requested. Pilots should respond to a weather advisory by either acknowledging the advisory or by acknowledging the advisory and requesting an alternative course of action as follows: 10.2.1.1 Request to deviate off course by stating the number of miles and the direction of the requested deviation. In this case, when the requested deviation is approved the pilot is expected to provide his/her own navigation, to maintain the altitude assigned by ATC, and to remain within the specified mileage of his/her original course. 10.2.1.2 Request a new route to avoid the affected area. 10.2.1.3 Request a change of altitude. 10.2.1.4 Request radar vectors around the affected areas. 10.2.2 For obvious reasons of safety, an IFR pilot must not deviate from the course or altitude/flight level without a proper ATC clearance. When weather conditions encountered are so severe that an immediate deviation is determined to be necessary and time will not permit approval by ATC, the pilot's emergency authority may be exercised. 10.2.3 When the pilot requests clearance for a route deviation or for an ATC radar vector, the controller must evaluate the air traffic picture in the affected area and coordinate with other controllers (if ATC jurisdictional boundaries may be crossed) before replying to the request. 10.2.4 It should be remembered that the controller's primary function is to provide safe separation between aircraft. Any additional service, such as weather avoidance assistance, can only be provided to the extent that it does not derogate the primary function. It is also worth noting that the separation workload is generally greater than normal when weather disrupts the usual flow of traffic. ATC radar limitations and frequency congestion may also be factors in limiting the controller's capability to provide additional service. 10.2.5 It is very important that the request for deviation or radar vector be forwarded to ATC as far in advance as possible. Delay in submitting it may delay or even preclude ATC approval or require that additional restrictions be placed on the clearance. Insofar as possible, the following information should be furnished to ATC when requesting clearance to detour around weather activity: 10.2.5.1 Proposed point where detour will commence. 10.2.5.2 Proposed route and extent of detour (direction and distance). 10.2.5.3 Point where original route will be resumed. 10.2.5.4 Flight conditions (IFR or VFR). 10.2.5.5 Any further deviation that may become necessary as the flight progresses. 10.2.5.6 Advise if the aircraft is equipped with functioning airborne radar. 10.2.6 To a large degree, the assistance that might be rendered by ATC will depend upon the weather information available to controllers. Due to the extremely transitory nature of severe weather situations, the controller's weather information may be of only limited value if based on weather observed on radar only. Frequent updates by pilots giving specific information as to the area affected, altitudes, intensity, and nature of the severe weather can be of considerable value. Such reports are relayed by radio or phone to other pilots and controllers, and they also receive widespread teletypewriter dissemination. 30 AUG 07 AIP United States of America GEN 3.5-31 15 MAR 07 Federal Aviation Administration Nineteenth Edition 10.2.7 Obtaining IFR clearance or an ATC radar vector to circumnavigate severe weather can often be accommodated more readily in the en route areas away from terminals because there is usually less congestion and, therefore, greater freedom of action. In terminal areas, the problem is more acute because of traffic density, ATC coordination requirements, complex departure and arrival routes, and adjacent airports. As a consequence, controllers are less likely to be able to accommodate all requests for weather detours in a terminal area or be in a position to volunteer such routes to the pilot. Nevertheless, pilots should not hesitate to advise controllers of any observed severe weather and should specifically advise controllers if they desire circumnavigation of observed weather. 10.3 ATC Severe Weather Avoidance Plans 10.3.1 Air Route Traffic Control Centers and some Terminal Radar Control facilities utilize plans for severe weather avoidance within their control areas. Aviation-oriented meteorologists provide weather information. Preplanned alternate route packages developed by the facilities are used in conjunction with flow restrictions to ensure a more orderly flow of traffic during periods of severe or adverse weather conditions. 10.3.2 During these periods, pilots may expect to receive alternative route clearances. These routes are predicated upon the forecasts of the meteorologist and coordination between the Air Traffic Control System Command Center and the other centers. The routes are utilized as necessary in order to allow as many aircraft as possible to operate in any given area, and frequently they will deviate from the normal preferred routes. With user cooperation, this plan may significantly reduce delays. 10.4 Procedures for Weather Deviations and Other Contingencies in Oceanic Controlled Airspace 10.4.1 When the pilot initiates communications with ATC, rapid response may be obtained by stating “WEATHER DEVIATION REQUIRED” to indicate priority is desired on the frequency and for ATC response. _ 10.4.2 The pilot still retains the option of initiating the communications using the urgency call “PAN- PAN” three times to alert all listening parties of a special handling condition which will receive ATC priority for issuance of a clearance or assistance. 10.4.3 ATC will:_ 10.4.3.1 Approve the deviation, or 10.4.3.2 Provide vertical separation and then approve the deviation, or 10.4.3.3 If ATC is unable to establish vertical separation, ATC shall advise the pilot that standard separation cannot be applied; provide essential traffic information for all affected aircraft, to the extent practicable; and if possible, suggest a course of action. ATC may suggest that the pilot climb or descend to a contingency altitude (1,000 feet above or below that assigned if operating above FL 290; 500_feet above or below that assigned if operating at or below FL 290). PHRASEOLOGY- STANDARD SEPARATION NOT AVAILABLE; DEVIATE AT PILOT'S DISCRETION; SUGGEST CLIMB (or descent) TO (appropriate altitude); TRAFFIC (position and altitude); REPORT DEVIATION COMPLETE. 10.4.4 The pilot will follow the ATC advisory altitude when approximately 10 NM from track as well as execute the procedures detailed in para- graph_10.4.5. 10.4.5 If contact cannot be established or a revised ATC clearance or advisory is not available and deviation from track is required, the pilot shall take the following actions: 10.4.5.1 If possible, deviate away from an organized track or route system. 10.4.5.2 Broadcast aircraft position and intentions on the frequency in use, as well as on frequency 121.5_MHz at suitable intervals stating: flight identification (operator call sign), flight level, track code or ATS route designator, and extent of deviation expected. 10.4.5.3 Watch for conflicting traffic both visually and by reference to the Traffic Alert and Collision Avoidance System (TCAS), if equipped. 10.4.5.4 Turn on aircraft exterior lights. 10.4.5.5 Deviations of less than 10 NM or operations within COMPOSITE (NOPAC and CEPAC) Air- 30 AUG 07 AIP United States of America GEN 3.5-32 15 MAR 07 Federal Aviation Administration Nineteenth Edition space, should REMAIN at ASSIGNED altitude. Otherwise, when the aircraft is approximately 10 NM from track, initiate an altitude change based upon the following criteria: TBL GEN 3.5-4 Route Centerline/Track Deviations >10 NM Altitude Change East 000 - 179_M Left Right Descend 300 Feet Climb 300 Feet West 180-359_M Left Right Climb 300 Feet Descend 300 Feet Pilot Memory Slogan: “East right up, West right down.” 10.4.5.6 When returning to track, be at the assigned flight level when the aircraft is within approximately 10 NM of centerline. 10.4.5.7 If contact was not established prior to deviating, continue to attempt to contact ATC to obtain a clearance. If contact was established, continue to keep ATC advised of intentions and obtain essential traffic information. 11. Notifications Required From Operators 11.1 Preflight briefing and flight documentation services provided by AFSSs do not require prior notification. 11.2 Preflight briefing and flight documentation services provided by a National Weather Service Office (or contract office) are available upon request for long-range international flights for which meteorological data packages are prepared for the pilot-in-command. Briefing times should be coordi- nated between the local representative and the local meteorological office. 11.3 Flight Service Stations do not normally have the capability to prepare meteorological data packages for a preflight briefing. 12. Weather Observing Systems and Operating Procedures For surface wind readings, most meteorological reporting stations have a direct reading, 3-cup anemometer wind system for which a 1-minute mean wind speed and direction (based on true north) is taken. Some stations also have a continuous wind speed recorder which is used in determining the gustiness of the wind. 13. Runway Visual Range (RVR) There are currently two configurations of the RVR, commonly identified as Taskers and New Generation RVR. The Taskers use transmissometer technology. The New Generation RVRs use forward scatter technology and are currently being deployed to replace the existing Taskers. 13.1 RVR values are measured by transmissometers mounted on 14-foot towers along the runway. A full RVR system consists of: 13.1.1 A transmissometer projector and related items. 13.1.2 A transmissometer receiver (detector) and related items. 13.1.3 An analogue recorder. 13.1.4 A signal data converter and related items. 13.1.5 A remote digital or remote display program- mer. 13.2 The transmissometer projector and receiver are mounted on towers 250 feet apart. A known intensity of light is emitted from the projector and is measured by the receiver. Any obscuring matter, such as rain, snow, dust, fog, haze, or smoke, reduces the light intensity arriving at the receiver. The resultant intensity measurement is then converted to an RVR value by the signal data converter. These values are displayed by readout equipment in the associated air traffic facility and updated approximately once every minute for controller issuance to pilots. 13.3 The signal data converter receives information on the high-intensity runway edge light setting in use (step 3, 4, or 5), transmission values from the transmissometer, and the sensing of day or night conditions. From the three data sources, the system will compute appropriate RVR values. 13.4 An RVR transmissometer established on a 250-foot baseline provides digital readouts to a minimum of 600 feet, which are displayed in 200-foot increments to 3,000 feet, and in 500-foot increments from 3,000 feet to a maximum value of 6,000 feet. 13.5 RVR values for Category IIIa operations extend down to 700-foot RVR; however, only 600 and 800_feet are reportable RVR increments. The 800_RVR reportable value covers a range of 701 feet to 900 feet and is therefore a valid minimum indication of Category IIIa operations.

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30 AUG 07 AIP United States of America GEN 3.5-33 15 MAR 07 Federal Aviation Administration Nineteenth Edition 13.6 Approach categories with the corresponding minimum RVR values are listed in TBL GEN 3.5-5. TBL GEN 3.5-5 Approach Category/Minimum RVR Table Category Visibility (RVR) Nonprecision 2,400 feet Category I 1,800 feet Category II 1,200 feet Category IIIa 700_ feet Category IIIb 150 feet Category IIIc _0_feet 13.7 Ten-minute maximum and minimum RVR values for the designated RVR runway are reported in the body of the aviation weather report when the prevailing visibility is less than 1 mile and/or the RVR is 6,000 feet or less. ATCTs report RVR when the prevailing visibility is 1 mile or less and/or the RVR is 6,000 feet or less. 13.8 Details on the requirements for the operational use of RVR are contained in FAA Advisory Circular_97-1, “Runway Visual Range (RVR).” Pilots are responsible for compliance with minimums prescribed for their class of operations in appropriate Federal Aviation Regulations and/or operations specifications. 13.8.1 RVR values are also measured by forward scatter meters mounted on 14-foot frangible fiberglass poles. A full RVR system consists of: 13.8.1.1 Forward scatter meter with a transmitter, receiver and associated items. 13.8.1.2 A runway light intensity monitor (RLIM). 13.8.1.3 An ambient light sensor (ALS). 13.8.1.4 A data processor unit (DPU). 13.8.1.5 A controller display (CD). 13.8.2 The forward scatter meter is mounted on a 14-foot frangible pole. Infrared light is emitted from the transmitter and received by the receiver. Any obscuring matter such as rain, snow, dust, fog, haze, or smoke increases the amount of scattered light reaching the receiver. The resulting measurement along with inputs from the runway light intensity monitor and the ambient light sensor are forwarded to the DPU which calculates the proper RVR value. The RVR values are displayed locally and remotely on controller displays. 13.8.3 The runway light intensity monitors both the runway edge and centerline light step settings (steps_1 through 5). Centerline light step settings are used for CAT IIIb operations. Edge light step settings are used for CAT I, II, and IIIa operations. 13.8.4 New Generation RVRs can measure and display RVR values down to the lowest limits of Category IIIb operations (150 foot RVR). RVR values are displayed in 100-foot increments and are reported as follows: 13.8.4.1 100-foot increments for products below 800 feet. 13.8.4.2 200-foot increments for products between 800 feet and 3,000 feet. 13.8.4.3 500-foot increments for products between 3,000 feet and 6,500 feet. 13.8.4.4 25-meter increments for products below 150 meters. 13.8.4.5 50-meter increments for products between 150 meters and 800 meters. 13.8.4.6 100-meter increments for products between 800 meters and 1,200 meters. 13.8.4.7 200-meter increments for products between 1,200 meters and 2,000 meters. 14. Reporting of Cloud Heights 14.1 Ceiling, by definition in Federal Aviation Regulations, and as used in Aviation Weather Reports and Forecasts, is the height above ground (or water) level of the lowest layer of clouds or obscuring phenomenon that is reported as “broken,” “overcast,” or “the vertical visibility into an obscuration.” For example, an aerodrome forecast which reads “BKN030” refers to heights above ground level (AGL). An area forecast which reads “BKN030” states that the height is above mean sea level (MSL). See FIG GEN 3.5-23 for the Key to Routine Aviation Weather Reports and Forecasts for the definition of “broken,” “overcast,” and “obscuration.”_ 14.2 Information on cloud base height is obtained by use of ceilometers (rotating or fixed beam), ceiling lights, ceiling balloons, pilot reports, and observer estimations. The systems in use by most reporting stations are either the observer estimation or the rotating beam ceilometer. 30 AUG 07 AIP United States of America GEN 3.5-34 15 MAR 07 Federal Aviation Administration Nineteenth Edition 14.3 Pilots usually report height values above mean sea level, since they determine heights by the altimeter. This is taken into account when disseminat- ing and otherwise applying information received from pilots. (“Ceiling” heights are always above ground level.) In reports disseminated as pilot reports, height references are given the same as received from pilots; that is, above mean sea level. 14.4 In area forecasts or inflight Advisories, ceilings are denoted by the contraction “CIG” when used with sky cover symbols as in “LWRG TO CIG OVC005,” or the contraction “AGL” after the forecast cloud height value. When the cloud base is given in height above mean sea level, it is so indicated by the contraction “MSL” or “ASL” following the height value. The heights of cloud tops, freezing level, icing, and turbulence are always given in heights above mean sea level (ASL or MSL). 15. Reporting Prevailing Visibility 15.1 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: 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: M1 /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 condi- tion; e.g., fog, haze, smoke, etc., or combinations thereof. 15.2 Prevailing visibility is the greatest visibility equalled or exceeded throughout at least one-half 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. 15.3 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. 16. Estimating Intensity of Rain and Ice Pellets 16.1 Rain 16.1.1 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. 16.1.2 Moderate. Individual drops are not clearly identifiable; spray is observable just above pave- ments and other hard surfaces. 16.1.3 Heavy. Rain seemingly falls in sheets; individual drops are not identifiable; heavy spray to a height of several inches is observed over hard surfaces. 16.2 Ice Pellets 16.2.1 Light. Scattered pellets that do not com- pletely cover an exposed surface regardless of duration. Visibility is not affected. 16.2.2 Moderate. Slow accumulation on the ground. Visibility is reduced by ice pellets to less than 7 statute miles. 16.2.3 Heavy. Rapid accumulation on the ground. Visibility is reduced by ice pellets to less than 3 statute miles. 17. Estimating the Intensity of Snow or Drizzle (Based on Visibility) 17.1 Light. Visibility more than 1 /2 statute mile. 17.2 Moderate. Visibility from more than 1 /4 statute mile to 1 /2 statute mile. 17.3 Heavy. Visibility 1 /4 statute mile or less. 18. Pilot Weather Reports (PIREPs) 18.1 FAA air traffic facilities are required to solicit PIREPs 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 a light degree or greater, turbulence of a moderate degree or greater, wind shear, and reported or forecast volcanic ash clouds. 30 AUG 07 AIP United States of America GEN 3.5-35 15 MAR 07 Federal Aviation Administration Nineteenth Edition 18.2 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 (haze, smoke, and dust), wind at altitude, and temperature aloft. 18.3 PIREPs should be given to the ground facility with which communications are established; i.e., EFAS, AFSS/FSS, ARTCC, or terminal ATC. Radio call “FLIGHT WATCH,” which serves as a collection point for the exchange of PIREPs with en route aircraft, is one of the primary duties of EFAS facilities. 18.4 If pilots do not make PIREPs by radio, it is helpful if, upon landing, they report to the nearest AFSS/FSS or Weather Forecast Office the inflight conditions which they encountered. Some of the uses made of the reports are: 18.4.1 The ATCT uses the reports to expedite the flow of air traffic in the vicinity of the field and for hazardous weather avoidance procedures. 18.4.2 The AFSS/FSS uses the reports to brief other pilots, to provide inflight advisories and weather avoidance information to en route aircraft. 18.4.3 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. 18.4.4 The NWS uses the reports to verify or amend conditions contained in aviation forecasts and advisories; (In some cases, pilot reports of hazardous conditions are the triggering mechanism for the issuance of advisories.) 18.4.5 The NWS, other government organizations, the military, and private industry groups use PIREPs for research activities in the study of meteorological phenomena. 18.4.6 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. 18.5 The FAA, NWS, and other organizations that enter PIREPs into the weather reporting system use the format listed in TBL GEN 3.5-6, PIREP Element Code Chart. Items 1 through 6 are included in all transmitted PIREPs along with one or more of items 7 through 13. Although the PIREP should be as complete and concise as possible, pilots should not be overly concerned with strict format or phraseology. The important thing is that the information is relayed so other pilots may benefit from your observation. If a portion of the report needs clarification, the ground station will request the information. 18.6 Completed PIREPs will be transmitted to weather circuits as in the following examples: EXAMPLE- KCMH UA/OV APE 230010/TM 1516/FL085/TP BE20/SK BKN065/WX FV03SM HZ FU/TA 20/TB LGT. Translation: one zero miles southwest of Appleton VOR; time 1516 UTC; altitude eight thousand five hundred; aircraft type BE20; base 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- KCRW UA/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. Translation: 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. 30 AUG 07 AIP United States of America GEN 3.5-36 15 MAR 07 Federal Aviation Administration Nineteenth Edition TBL GEN 3.5-6 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 paragraph 22 12. Icing /IC See paragraph 20 13. Remarks /RM For reporting elements not included or to clarify previously reported items 30 AUG 07 AIP United States of America GEN 3.5-37 15 MAR 07 Federal Aviation Administration Nineteenth Edition 19. Mandatory MET Points 19.1 Within the ICAO CAR/SAM Regions and within the U.S. area of responsibility, several mandatory MET reporting points have been established. These points are located within the Houston, Miami, and San Juan Flight Information Regions (FIR). These points have been established for flights between the South American and Caribbean Regions and Europe, Canada and the U.S. 19.2 Mandatory MET Reporting Points Within the Houston FIR Point For Flights Between ABBOT Acapulco and Montreal, New York, Toronto, Mexico City and New Orleans. ALARD New Orleans and Belize, Guatemala, San Pedro Sula, Mexico City and Miami, Tampa. ARGUS Toronto and Guadalajara, Mexico City, New Orleans and Mexico City. SWORD Dallas-Fort Worth, New Orleans, Chicago and Cancun, Cozumel, and Central America. 19.3 Mandatory MET Reporting Points Within the Miami FIR Point For Flights Between Grand Turk New York and Aruba, Curacao, Kingston, Miami and Belem, St. Thomas, Rio de Janeiro, San_Paulo, St._Croix, Kingston and Bermuda. GRATX Madrid and Miami, Havana.

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MAPYL New York and Guayaquil, Montego Bay, Panama, Lima, Atlanta and San Juan. RESIN New Orleans and San Juan. SLAPP New York and Aruba, Curacao, Kingston, Port-au-Prince. Bermuda and Freeport, Nassau. New York and Barranquilla, Bogota, Santo Domingo, Washington and Santo Domingo, Atlanta and San_Juan. 19.4 Mandatory MET Reporting Points Within the San Juan FIR Point For Flights Between GRANN Toronto and Barbados, New York and Fort de France. At intersection of routes A321, A523, G432. KRAFT San Juan and Buenos Aires, Caracas, St. Thomas, St. Croix, St. Maarten, San Juan, Kingston and Bermuda. PISAX New York and Barbados, Fort de France, Bermuda and Antigua, Barbados. 30 AUG 07 AIP United States of America GEN 3.5-38 15 MAR 07 Federal Aviation Administration Nineteenth Edition TBL GEN 3.5-7 Intensity Ice Accumulation Trace Ice becomes perceptible. Rate of accumulation slightly greater than rate of sublimation. Deicing/anti-icing equipment is not utilized unless encountered for an extended period of time (over 1 hour). Light The rate of accumulation may create a problem if flight is prolonged in this environment (over 1_hour). Occasional use of deicing/anti-icing equipment removes/prevents accumulation. It does not present a problem if the deicing/anti-icing equipment is used. Moderate The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or diversion is necessary. Severe The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary. Pilot Report: Aircraft Identification, Location, Time (UTC), Intensity of Type1 , Altitude/FL, Aircraft Type, Indicated Air Speed (IAS), and Outside Air Temperature (OAT)2 . 1 Rime or Clear Ice: Rime ice is a rough, milky, opaque ice formed by the instantaneous freezing of small supercooled water droplets. Clear ice is a glossy, clear, or translucent ice formed by the relatively slow freezing of large supercooled water droplets.

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2 The Outside Air Temperature (OAT) should be requested by the AFSS/FSS or ATC if not included in the PIREP. 20. PIREPs Relating to Airframe Icing 20.1 The effects of ice accretion on aircraft are: cumulative-thrust is reduced, drag increases, lift lessens, weight increases. The results are an increase in stall speed and a deterioration of aircraft performance. In extreme cases, 2 to 3 inches of ice can form on the leading edge of the airfoil in less than 5 minutes. It takes but 1 /2 inch of ice to reduce the lifting power of some aircraft by 50 percent and to increase the frictional drag by an equal percentage. 20.2 A pilot can expect icing when flying in visible precipitation, such as rain or cloud droplets, and the temperature is between +02 and -10 degrees Celsius. When icing is detected, a pilot should do one of two things (particularly if the aircraft is not equipped with deicing equipment). The pilot should get out of the area of precipitation or go to an altitude where the temperature is above freezing. This “warmer” altitude may not always be a lower altitude. Proper preflight action includes obtaining information on the freezing level and the above-freezing levels in precipitation areas. Report the icing to an ATC or FSS facility, and if operating IFR, request new routing or altitude if icing will be a hazard. Be sure to give the type of aircraft to ATC when reporting icing. TBL GEN 3.5-7, describes how to report icing conditions.

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30 AUG 07 AIP United States of America GEN 3.5-39 15 MAR 07 Federal Aviation Administration Nineteenth Edition 21. Definitions of Inflight Icing Terms See TBL GEN 3.5-8, Icing Types, and TBL GEN 3.5-9, Icing Conditions. TBL GEN 3.5-8 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.

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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 AIP for use in the “Remarks” section of the PIREP and for use in forecasting. 30 AUG 07 AIP United States of America GEN 3.5-40 15 MAR 07 Federal Aviation Administration Nineteenth Edition TBL GEN 3.5-9 Icing Conditions Appendix C Icing Conditions Appendix C (14 CFR, Part 25 and 29) is the certification icing condition standard for approving ice protection provisions on aircraft. The conditions are specified in terms of altitude, temperature, liquid water content (LWC), representative droplet size (mean effective drop diameter [MED]), and cloud horizontal extent. Forecast Icing Conditions Environmental conditions expected by a National Weather Service or an FAA-approved weather provider to be conducive to the formation of inflight icing on aircraft. Freezing Drizzle (FZDZ) Drizzle is precipitation at ground level or aloft in the form of liquid water drops which have diameters less than 0.5 mm and greater than 0.05 mm. Freezing drizzle is drizzle that exists at air temperatures less than 0_C (supercooled), remains in liquid form, and freezes upon contact with objects on the surface or airborne. Freezing Precipitation Freezing precipitation is freezing rain or freezing drizzle falling through or outside of visible cloud.

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Freezing Rain (FZRA) Rain is precipitation at ground level or aloft in the form of liquid water drops which have diameters greater than 0.5 mm. Freezing rain is rain that exists at air temperatures less than 0_C (supercooled), remains in liquid form, and freezes upon contact with objects on the ground or in the air. Icing in Cloud Icing occurring within visible cloud. Cloud droplets (diameter < 0.05 mm) will be present; freezing drizzle and/or freezing rain may or may not be present. Icing in Precipitation Icing occurring from an encounter with freezing precipitation, that is, supercooled drops with diameters exceeding 0.05 mm, within or outside of visible cloud. Known Icing Conditions Atmospheric conditions in which the formation of ice is observed or detected in flight. Note- Because of the variability in space and time of atmospheric conditions, the existence of a report of observed icing does not assure the presence or intensity of icing conditions at a later time, nor can a report of no icing assure the absence of icing conditions at a later time. Potential Icing Conditions Atmospheric icing conditions that are typically defined by airframe manufacturers relative to temperature and visible moisture that may result in aircraft ice accretion on the ground or in flight. The potential icing conditions are typically defined in the Airplane Flight Manual or in the Airplane Operation Manual. Supercooled Drizzle Drops (SCDD) Synonymous with freezing drizzle aloft. Supercooled Drops or /Droplets Water drops/droplets which remain unfrozen at temperatures below 0 _C. Supercooled drops are found in clouds, freezing drizzle, and freezing rain in the atmosphere. These drops may impinge and freeze after contact on aircraft surfaces. Supercooled Large Drops (SLD) Liquid droplets with diameters greater than 0.05 mm at temperatures less than 0_C, i.e., freezing rain or freezing drizzle.