Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 6-9. AAWU Flight Advisory and Area Forecast Zones - Alaska
Table 6-4. AAWU Flight Advisory and Area Forecast Zones – Alaska 1 Arctic Coast Coastal 14 Southern Southeast Alaska 2 North Slopes of the Brooks Range 15 Coastal Southeast Alaska 3 Upper Yukon Valley 16 Eastern Gulf Coast 4 Koyukuk and Upper Kobuk Valley 17 Copper River Basin 5 Northern Seward Peninsula-Lower Kobuk Valley 18 Cook Inlet-Susitna Valley 6 Southern Seward Peninsula-Eastern Norton Sound 19 Central Gulf Coast 7 Tanana Valley 20 Kodiak Island 8 Lower Yukon Valley 21 Alaska Peninsula-Port Heiden to Unimak Pass 9 Kuskowim Valley 22 Unimak Pass to Adak 10 Yukon-Kuskowim Delta 23 St. Lawrence Island-Bering Sea Coast 11 Bristol Bay 24 Adak to Attu 12 Lynn Canal and Glacier Bay 25 Pribilof Islands and Southeast Bering Sea 13 Central Southeast Alaska
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 6-10. WFO Honolulu AIRMET Areas of Responsibility - Hawaii
6.2.2 AIRMET Issuance Criteria An AIRMET may be issued when any of the following weather phenomena are occurring or expected to occur over an area of at least 3,000 square miles:
• Ceiling less than 1,000 feet and/or visibility less than 3 statute miles (IFR)
o Weather phenomena restricting the visibility including, but not limited to, precipitation (PCPN), smoke (FU), haze (HZ), mist (BR), fog (FG), and blowing snow (BS).
• Widespread mountain obscuration (MTN OBSCN)
o Weather phenomena causing the obscurement are included, but limited to clouds (CLDS), precipitation (PCPN), smoke (FU), haze (HZ), mist (BR), and fog (FG).
• Moderate turbulence (MOD TURB)
o Top and bottom of MOD TURB layer are specified.
• Sustained surface wind greater than 30 knots (STG SFC WND)
• Moderate icing (MOD ICE)
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) o Top and bottom of MOD ICE are specified.
o The range of freezing level altitudes is given when the bottom altitude of MOD ICE is the freezing level (FRZLVL).
o Areas with multiple freezing levels are specified.
o Range of freezing levels over the area is specified.
o Lowest freezing levels above ground level (AGL) at intervals of 4,000 feet AMSL (or SFC as appropriate) are specified.
• Non-convective low-level wind shear potential below 2,000 feet AGL (LLWS POTENTIAL).
6.2.3 AIRMET Standardization All AIRMETs follow these standards:
• All heights or altitudes are referenced to above mean sea level (AMSL), unless otherwise noted, and annotated using the height in hundreds of feet, consisting of three digits (e.g., 040). For heights at or above 18,000 feet, the level is preceded by FL to represent flight levels (e.g., FL180).
• Messages are prepared in abbreviated plain language using contractions from the Federal Aviation Administration (FAA) Order 7340.1Z. A limited number of nonabbreviated words, geographical names and numerical values of a self-explanatory nature may also be used.
• Weather and obstructions to visibility are described using the weather abbreviations for surface weather observations (METAR/SPECI). See the Federal Meteorological Handbook (FMH) No. 1 – Surface Observations or Section 3.1 of this document.
Note: Refer to Appendix A for definitions of common terms used in AIRMETs.
6.2.4 AIRMET Bulletins, Issuance Times, and Valid Period AIRMETs are issued as bulletins containing one or more AIRMET messages following the schedule listed below. Unscheduled AIRMETs are issued when conditions are occurring or expected to occur, but were not forecast.
Table 6-5. AIRMET Issuance Schedule 1st Scheduled Issuance (UTC) 2nd Scheduled Issuance (UTC) 3rd Scheduled Issuance (UTC) 4th Scheduled Issuance (UTC) CONUS 0245 0845 1445 2045 Alaska 0145 (DT)/ 0245 (ST) 0745 (DT)/ 0845 (ST) 1345 (DT)/ 1445 (ST) 1945 (DT)/ 2045 (ST) Hawaii 0400 1000 1600 2200 Note: DT - Daylight Time, ST - Standard Time
AIRMETs are valid for no more than 6 hours. The valid period of an AIRMET message cannot exceed the valid time of the AIRMET bulletin. However, note that each AIRMET contains remarks concerning the continuance of the phenomenon during the six (6) hours following the AIRMET ending time. Also, AIRMET bulletins can contain a separate outlook when conditions AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-24
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) meeting AIRMET criteria are expected to occur during the 6-hour period after the valid time of the AIRMET bulletin.
6.2.5 AIRMET Format An AIRMET message includes the following information as appropriate and in the order indicated:
• Reference to appropriate active SIGMETs affecting the area at the time of AIRMET issuance (e.g., SEE SIGMET BRAVO SERIES).
• Beginning time of the AIRMET phenomenon if different from the AIRMET beginning valid time.
• AIRMET name (SIERRA, TANGO or ZULU), update number, weather phenomenon, and ending valid time (Note: the AIRMET number is reset to one (1) after 0000 UTC each day).
o AIRMET Sierra describes IFR conditions and/or extensive mountain obscurations
o AIRMET Tango describes moderate turbulence, sustained surface winds of 30 knots or greater and non-convective low-level wind shear.
o AIRMET Zulu describes moderate icing and provides freezing level heights
• List of affected states (CONUS only).
• Location of phenomenon using VORs or other well known geographic features.
• Description of phenomenon for the AIRMET issuance.
• Vertical extent (bases and tops), as appropriate.
• Ending time of phenomenon if different from the AIRMET ending time.
• Remarks concerning the continuance of the phenomenon during the six (6) hours following the AIRMET ending time.
• CONUS and Hawaii AIRMETs: A separate AIRMET outlook is included in the AIRMET bulletin when conditions meeting AIRMET criteria are expected to occur during the 6- hour period after the valid time of the AIRMET bulletin.
• Alaska AIRMETs: Outlook information is included in the appropriate Area Forecast zone when conditions are expected to occur during the 6-hour period after the valid time of the AIRMET bulletin.
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-25
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) LINE 1 BOSS WA 211945 2 AIRMET SIERRA UPDT 3 FOR IFR AND MIN OBSCN VALID UNTIL 220200 ЗА AIRMET IFR..ME NH VT MA CT RI NY NJ AND CSTL WTRS 4A FROM CAR TO YSJ TO 150E ACK TO EWR TO YOW TO CAR SA OCNL CIG BLW 010/VIS BLW 3SM PCPN/BR. CONDS CONT BYD 02Z THRU 082.
ЗВ AIRMET MIN OBSCN..ME NH VT MA NY PA 4B FROM CAR TO MLT TO CON TO SLT TO SYR TO CAR 5B MINS ONLY OBSCD BY CLDS/PCPN/BR. CONDS CONT BYD 02Z THRU 08Z.
Figure 6-11. AIRMET Bulletin Decoding Example Table 6-6. Decoding an AIRMET Bulletin Line Content Description 1 BOS AIRMET area identifier S AIRMET series WA Product type 211945 Issuance UTC date/time 2 AIRMET Product type SIERRA AIRMET series UPDT 3 Update number FOR IFR AND MTN OBSCN Product description VALID UNTIL 220200 Ending UTC date/time ЗА AIRMET IFR..ME NH VI MA CT RI NY Product type/series...
NJ AND CSTL WTRS Phenomenon location ЗВ AIRMET MIN OBSCN..ME NH VT MA NY (states) 4A FROM CAR TO YSJ TO 150E ACK TO EWR Phenomenon location TO YOW TO CAR (VOR locations) 4B FROM CAR TO MLT TO CON TO SIT TO
SYR TO CAR 5A CIG BLW 010/VIS BLW 3SM PCPN/BR. Phenomenon description CONDS CONT BYD 02Z THRU 08Z.
5B MINS OBSCD BY CLDS/PCPN/BR. CONDS CONT BYD 02Z THRU 08Z.
The AIRMET bulletin in Figure 6-11 is decoded as follows:
(Line 1) AIRMET SIERRA issued for the Boston area at 1945Z on the 21s day of the month.
"SIERRA" contains information on Instrument Flight Rules (IFR) and/or mountain obscurations.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) (Line 2) This is the third updated issuance of this Boston AIRMET series as indicated by “SIERRA UPDT 3” and is valid until 0200Z on the 22nd.
(Line 3A) The affected states within the BOS area are: Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island, New York, New Jersey, and coastal waters.
(Line 3B) The affected states within the BOS area are: Maine, New Hampshire, Vermont, Massachusetts, New York, and Pennsylvania.
(Line 4A) Within an area bounded by: Caribou, ME; to Saint Johns, New Brunswick; to 150 nautical miles east of Nantucket, MA; to Newark, NJ; to Ottawa, Ontario; to Caribou, ME
(Line 4B) Within an area bounded by: Caribou, ME to Millinocket, ME to Concord, NH to Slate Run, PA to Syracuse, NY to Caribou, ME
(Line 5A) Ceiling below 1,000 feet/visibility below 3 statute miles, precipitation/mist. Conditions continuing beyond 0200Z through 0800Z.
(Line 5B) Mountains Obscured by clouds, precipitation and mist. Conditions continuing beyond 0200Z through 0800Z.
6.2.5.1 AIRMET Updates and Amendments If an AIRMET is amended, AMD is added after the date/time group on the FAA product line.
The update number will be incremented, UPDT is added to end of the line containing the list of affected states (CONUS only). The issuance time of the AIRMET bulletin is updated to reflect the time of the amendment. The ending valid time remains unchanged.
6.2.5.2 AIRMET Corrections AIRMETs containing errors are corrected by adding COR after the date/time group on the FAA product line. The issuance time of the AIRMET bulletin is updated to reflect the time of the correction. The ending valid time remains unchanged.
6.2.6 AIRMET Examples
6.2.6.1 CONUS AIRMET Example
WAUS43 KKCI 091445 CHIZ WA 091445 AIRMET ZULU UPDT 4 FOR ICE AND FRZLVL VALID UNTIL 092100 AIRMET ICE...KS IA MO IL FROM 30WSW FOD TO DBQ TO 50NW DEC TO 50SW FAM TO OSW TO MKC TO 30WSW FOD MOD ICE BTN FRZLVL AND FL200. FRZLVL 060-100. CONDS ENDG BY 21Z.
.
OTLK VALID 2100-0300Z...ICE IA MO WI IL IN KY BOUNDED BY BAE-BVT-PXV-50SW FAM-50NW DEC-DBQ-BAE MOD ICE BTN FRZLVL AND FL200. FRZLVL 080-100. CONDS CONTG THRU 03Z.
.
FRZLVL...RANGING FROM SFC-120 ACRS AREA MULT FRZLVL 015-085 BOUNDED BY 40W INL-YQT-SSM-70NNE AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-27
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) ASP-YVV-DXO-40NE FWA-40SSE BJI-40W INL SFC ALG 50NNW ISN-70W FAR-GFK-40NE ODI-40SW DXO 040 ALG ISN-70S BIS-30W ABR-30E ABR-60S FAR-30SW BRD-30NE FWA 080 ALG GLD-SLN-30W BDF-50S JOT-40SE IND-30SW CVG-40SW LOZ
AIRMET (WAUS43) issued by the Meteorological Watch Office (Aviation Weather Center) in Kansas City, Missouri on the 9th day of the month at 1445 UTC. This AIRMET (WA) is the Zulu series bulletin for the Chicago Area Forecast region (CHIZ) issued on the 9th day of the month at 1445 UTC. This is the 4th update to the Zulu series bulletin for icing and freezing levels and is valid until the 9th day of the month at 2100 UTC.
The first (and only) AIRMET noted within the bulletin is for icing affecting Kansas, Iowa, Missouri and Illinois. Within an area bounded from 30 nautical miles west-southwest of Fort Dodge, Iowa (FOD) to Dubuque, Iowa (DBQ) to 50 nautical miles northwest of Decatur, Illinois (DEC) to 50 nautical miles southwest of Farmington, Missouri (FAM) to Oswego, Kansas (OSW) to Kansas City, Missouri (MKC) to 30 nautical miles west-southwest of Fort Dodge, Iowa (FOD). Moderate icing between the freezing level and flight level 200 (approximately 20,000 feet MSL). The freezing level is between 6,000 feet MSL and 10,000 feet MSL. Conditions ending by 2100 UTC.
An outlook for icing between 2100 UTC to 0300 UTC exists over: Iowa, Missouri, Wisconsin, Illinois, Indiana and Kentucky. Within an area bounded by Milwaukee, Wisconsin (BAE) to Lafayette, Indiana (BVT) to Pocket City, Indiana (PXV) to 50 nautical miles southwest of Farmington, Missouri (FAM) to 50 nautical miles northwest of Decatur, Illinois (DEC) to Dubuque, Iowa (DBQ) to Milwaukee, Wisconsin (BAE). Moderate icing between the freezing level and flight level 200 (approximately 20,000 feet MSL). The freezing level is between 8,000 feet MSL and 10,000 feet MSL. Conditions continuing through 0300 UTC.
The freezing level ranges from the surface to 12,000 feet MSL across the Chicago Area Forecast region. Multiple freezing levels exist between 1,500 feet MSL and 8,500 feet MSL within an area bounded by 40 nautical miles west of International Falls, Minnesota (INL) to Thunder Bay, Ontario, Canada to Sault Saint Marie, Michigan (SSM) to 70 nautical miles northnortheast of Oscoda, Michigan (ASP) to Wiarton, Ontario, Canada to Detroit, Michigan (DXO) to 40 nautical miles northeast of Fort Wayne, Indiana (FWA) to 40 nautical miles south-southeast of Bemidji, Minnesota (BJI) to 40 nautical miles west of International Falls, Minnesota (INL).
The freezing level is at the surface along a line from 50 nautical miles north-northwest of Williston, North Dakota (ISN) to 70 nautical miles west of Fargo, North Dakota (FAR) to Grand Forks, North Dakota (GFK) to 40 nautical miles northeast of Nodine, Minnesota (ODI) to 40 nautical miles southwest of Detroit, Michigan (DXO). The freezing level is at 4,000 feet MSL along a line from Williston, North Dakota (ISN) to 70 nautical miles south of Bismarck, North Dakota (BIS) to 30 nautical miles west of Aberdeen, South Dakota (ABR) to 30 nautical miles east of Aberdeen, South Dakota (ABR) to 60 nautical miles south of Fargo, North Dakota (FAR) to 30 nautical miles southwest of Brainerd, Minnesota (BRD) to 30 nautical miles northeast of Fort Wayne, Indiana. The freezing level is 8,000 feet MSL along a line from Goodland, Kansas (GLD) to Salina, Kansas (SLN) to 30 nautical miles west of Bradford, Illinois (BDF) to 50 nautical miles south of Joliet, Illinois to 40 nautical miles southeast of Indianapolis, Indiana (IND) to 30 nautical miles southwest of Covington, Kentucky (CVG) to 40 nautical miles southwest of London, Kentucky (LOZ).
6.2.6.2 Hawaii AIRMET Example
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) WAHW31 PHFO 090945 WA0HI HNLT WA 091000 AIRMET TANGO UPDATE 1 FOR TURB VALID UNTIL 091600 AIRMET TURB...KAUAI OAHU MOLOKAI LANAI MAUI OVR AND IMDT N THRU E OF MTS.
MOD TURB BLW 100. CONDS CONTG BYD 1600Z.
AIRMET (WAHW31) issued by the Meteorological Watch Office (Weather Forecast Office) in Honolulu, Hawaii on the 9th day of the month at 0945 UTC. The National Weather Service AWIPS communication code for this product is WA0HI. This AIRMET (WA) is the Tango series bulletin for the Hawaii Area Forecast region (HNLT) issued on the 9th day of the month at 1000 UTC. This is the 1st update to the Tango series bulletin for turbulence and is valid until the 9th day of the month at 1600 UTC.
The first (and only) AIRMET noted within the bulletin is for turbulence affecting the islands of Kauai, Oahu, Molokai, Lanai and Maui, over and immediately north through east of the mountains. Moderate turbulence below 10,000 feet MSL. Conditions continuing beyond 1600 UTC.
6.2.6.3 Alaska AIRMET Example
WAAK47 PAWU 011740 WA7O JNUS WA 011740 AIRMET SIERRA FOR IFR AND MT OBSC VALID UNTIL 012100 .
LYNN CANAL AND GLACIER BAY JB W OF LYNN CANAL..MTS OCNL OBSC IN CLDS/PCPN.
SPRDG E. INTSF.
.
CNTRL SE AK JC PAOH−PAFE LN W..MTS OCNL OBSC IN CLDS/PCPN. SPRDG E. INTSF.
.
ERN GLF CST JE MTS OCNL OBSC IN CLDS/PCPN. IMPRG.
.
SE AK CSTL WTRS JF OCNL CIG BLW 010 VIS BLW 3SM SN BLSN. NC.
AIRMET (WAAK47) issued by the Meteorological Watch Office (Alaska Aviation Weather Unit) in Anchorage, Alaska on the 1st day of the month at 1740 UTC. The National Weather Service AWIPS communication code for this product is WA7O. This AIRMET (WA) is the Sierra series bulletin for the Juneau forecast area issued on the 1st day of the month at 1740 UTC. This is the AIRMET Sierra series for IFR and mountain obscuration valid until the 1st day of the month at 2100 UTC.
For the Lynn Canal and Glacier Bay forecast regions, Juneau region B...west of Lynn Canal…mountains occasionally obscured in clouds and precipitation. Conditions spreading east and intensifying during the forecast period.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
For the Central Southeast Alaska forecast region, Juneau region C…from a Hoonan, Alaska (PAOH) to Kake, Alaska (PAFE) line westward, mountains occasionally obscured in clouds and precipitation. Conditions spreading east and intensifying during the forecast period.
For the Eastern Gulf Coast forecast region, Juneau region E…Mountains occasionally obscured in clouds and precipitation. Conditions improving during the forecast period.
For the Southeast Alaska Coastal Waters, Juneau region F…Occasional ceiling below 1,000 feet AGL, visibility below 3 statute miles in snow and blowing snow. No change in conditions is expected during the forecast period.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
6.3 Center Weather Advisory (CWA) A Center Weather Advisory (CWA) is an aviation weather warning for conditions meeting or approaching national in-flight advisory (AIRMET, SIGMET or Convective SIGMET) criteria. The CWA is primarily used by aircrews to anticipate and avoid adverse weather conditions in the en route and terminal environments. CWAs are available on the Aviation Weather Center (AWC) web site at: http://aviationweather.gov/products/cwsu/.
6.3.1 CWA Issuance CWAs are issued by the NWS Center Weather Service Units (CWSUs). CWSU areas of responsibility in the contiguous U.S. are depicted on Figure 6-12. CWSU Anchorage area of responsibility for Alaska is depicted on Figure 6-13.
Figure 6-12. Center Weather Service Unit (CWSU) Areas of Responsibility, Contiguous U.S.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 6-13. CWSU Anchorage, AK (PAZA) Area of Responsibility
CWAs are valid for up to two (2) hours and may include forecasts of conditions expected to begin within two (2) hours of issuance. If conditions are expected to persist after the advisory’s valid period, a statement to that effect is included in the last line of the text. Additional CWAs will subsequently be issued as appropriate. Notice of significant changes in the phenomenon described in a CWA is provided by a new CWA issuance for that phenomenon. If the forecaster deems it necessary, CWAs may be issued hourly for convective activity.
6.3.2 CWA Communications Headers (UCWA / CWA) The Urgent CWA (UCWA) communications header is intended for those situations where weather conditions have an immediate effect on the safe flow of air traffic within the ARTCC area of responsibility. It is only used when the CWSU meteorologist believes any delay in dissemination to FAA facilities would impact aviation safety. The routine CWA header is used for subsequent issuances of the same phenomenon.
6.3.3 CWA Criteria CWAs are used in the four (4) following situations:
• Precede an Advisory o When the AWC has not yet issued an advisory, but conditions meet or will soon meet advisory criteria.
o In the case of an impending advisory, the CWA can be issued as an Urgent CWA (UCWA) to allow the fastest possible dissemination.
• Refine an existing Advisory o To supplement an existing AWC advisory for the purpose of refining or updating the location, movement, extent, or intensity of the weather event relevant to the ARTCC’s area of responsibility.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
• Highlight significant conditions not meeting Advisory criteria o When conditions do not meet advisory criteria, but conditions, in the judgment of the CWSU meteorologist, will adversely impact air traffic within the ARTCC area of responsibility.
• To cancel a CWA when the phenomenon described in the CWA is no longer expected.
6.3.4 CWA Format
Figure 6-14. Center Weather Advisory (CWA) Decoding Example
Table 6-7. Decoding a Center Weather Advisory (CWA) Line Content Description 1 ZDV ARTCC Identification 2 Phenomenon Number (single digit, 1-6) CWA Product Type (UCWA/CWA) 032140 Beginning and/or issuance UTC date/time 2 ZDV ARTCC Identification CWA Product Type 2 Phenomenon Number (single digit, 1-6) 02 Issuance Number (issued sequentially for each Phenomenon Number) VALID TIL 032340Z Ending valid UTC date/time 3 FROM FMN TO 10N FMN TO 20NE FMN TO 10E FMN TO FMN Phenomenon Location 4 ISOLD SEV TS NR FMN MOVG NEWD 10KTS. TOP FL410. WND GSTS TO 55KTS. HAIL TO 1 INCH RPRTD AT FMN. SEV TS CONTG BYD 2340Z Phenomenon Description
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