c. * * *
1.
* * *
2.
* * *
3. SIGMETs are identi.ed by an alphabetic designator from November through Yankee excluding Sierra and Tango. (Sierra, Tango, and Zulu are reserved for AIRMET text [WA] products; G-AIRMETS do not use the Sierra, Tango, or Zulu designators.) The .rst issuance of a SIGMET will be labeled as UWS (Urgent Weather SIGMET). * * *
d.
* * *
e.
* * *
1.
* * *
2.
The of.ces which issue international SIGMETs are:
(a) The AWC in Kansas City, Missouri. * * * * *
3. * * * The International SIGMET is issued for 6 hours for vol-canic 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 identi.ed by an alphabetic designator from Alpha through Mike and are numbered sequentially until that weather phenomenon ends. The criteria for an international SIG-MET are:
* * * * *
f. AIRMET
1. AIRMETs (WAs) are advisories of signi.cant weather phe-nomena but describe conditions at intensities lower than those which require the issuance of SIGMETs. AIRMETs are intended for dissemination to all pilots in the pre.ight and en route phase of .ight to enhance safety. AIRMET information is available in two formats: text bulletins (WA) and graphics (G-AIRMET). Both for-mats meet the criteria of paragraph 7-1-3i1 and are issued on a scheduled basis every 6 hours beginning at 0245 UTC. Unsched-uled updates and corrections are issued as necessary. AIRMETs contain details about IFR, extensive mountain obscuration, turbu-lence, strong surface winds, icing, and freezing levels.
* * * * *
2. * * *
(c) AIRMET Zulu describes moderate icing and provides freezing level heights.
Example of AIRMET Sierra issued for the Chicago FA area:
CHIS WA 131445
AIRMET SIERRA UPDT 2 FOR IFR AND MTN OBSCN VALID UNTIL 132100. AIRMET IFR...KY FROM 20SSW HNN TO HMV TO 50ENE DYR TO20SSW HNN CIG BLW 010/VIS BLW 3SM PCPN/BR/FG. CONDS ENDG BY
18Z.
AIRMET IFR....MN LS
FROM INL TO 70W YQT TO 40ENE DLH TO 30WNW DLH TO 50SE GFK TO 20 ENE GFK TO INL CIG BLW 010/VIS BLW 3SM BR. CONDS ENDG 15–18Z.
AIRMET IFR....KS
FROM 30N SLN TO 60E ICT TO 40S ICT TO 50W LBL TO 30SSW GLD TO 30N SLN CIG BLW 010/VIS BLW 3SM PCPN/BR/FG. CONDS ENDG 15–
18Z.
AIRMET MTN OBSCN...KY TN FROM HNN TO HMV TO GQO TO LOZ TO HNN MTN OBSC BY CLDS/PCPN/BR. CONDS CONTG BYD 21Z
THRU 03Z.
Example of AIRMET Tango issued for the Salt Lake City FA area:
SLCT WA 131445 AIRMET TANGO UPDT 2 FOR TURB VALID UNTIL 132100. AIRMET TURB...MT FROM 40NW HVR TO 50SE BIL TO 60E DLN TO 60SW YQL TO
40NW HVR MOD TURB BLW 150. CONDS DVLPG 18–21Z. CONDS CONTG BYD 21Z THRU 03Z.
AIRMET TURB....ID MT WY NV UT CO
FROM 100SE MLS TO 50SSW BFF TO 20SW BTY TO 40SW BAM TO 100SE MLS MOD TURB BTN FL310 AND FL410. CONDS CONTG BYD 21Z
ENDG 21–00Z.
AIRMET TURB...NV AZ NM CA AND CSTL WTRS FROM 100WSW ENI TO 40W BTY TO 40S LAS TO 30ESE TBE
TO INK TO ELP TO 50S TUS TO BZA TO 20S MZB TO 150SW PYE TO 100WSW ENI MOD TURB BTWN FL210 AND FL380. CONDS CONTG BYD
21Z THRU 03Z.
Example of AIRMET Zulu issued for the San Francisco FA area:
SFOZ WA 131445
AIRMET ZULU UPDT 2 FOR ICE AND FRZLVL VALID UNTIL
132100.
NO SGFNT ICE EXP OUTSIDE OF CNVTV ACT.
FRZLVL....RANGING FROM SFC–105 ACRS AREA
MULT FRZLVL BLW 080 BOUNDED BY 40SE YDC–60NNW
GEG–60SW MLP–30WSW BKE–20SW BAM–70W BAM–40SW
YKM–40E HUH–40SE YDC
SFC ALG 20NNW HUH–30SSE HUH–60S SEA 50NW LKV–
60WNWOAL–30SW OAL
040 ALG 40W HUH–30W HUH–30NNW SEA–40N PDX–20NNW
DSD
080 ALG 160NW FOT–80SW ONP–50SSW EUG 40SSE OED–
50SSE CZQ–60E EHF–40WSW LAS
3. Graphical AIRMETs (G-AIRMETs), found on the Aviation Weather Center webpage at http://aviationweather.gov, are graphical forecasts of en-route weather hazards valid at discrete times no more than 3 hours apart for a period of up to 12 hours into the future (for example, 00, 03, 06, 09, and 12 hours). Addi-tional forecasts may be inserted during the .rst 6 hours (for exam-ple, 01, 02, 04, and 05). 00 hour represents the initial conditions, and the subsequent graphics depict the area affected by the par-ticular hazard at that valid time. Forecasts valid at 00 through 06 hours correspond to the text AIRMET bulletin. Forecasts valid at 06 through 12 hours correspond to the text bulletin outlook. G-AIRMET depicts the following en route aviation weather hazards:
(a)
Instrument .ight rule conditions (ceiling <1,000 feet and/or surface visibility <3 miles)
(b)
Mountain obscuration
