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AIM

10/12/17

7−1−14

Meteorology

BYD 21Z THRU 03Z.

.....
EXAMPLE−

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−

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). Additional forecasts may be inserted during

the first 6 hours (for example, 01, 02, 04, and 05). 00

hour represents the initial conditions, and the

subsequent graphics depict the area affected by the

particular 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 flight rule conditions (ceiling

< 1000’ and/or surface visibility <3 miles)

(b) Mountain obscuration
(c) Icing
(d) Freezing level
(e) Turbulence
(f) Low level wind shear (LLWS)
(g) Strong surface winds

G−AIRMETs are snap shots at discrete time intervals

as defined above. The text AIRMET is the result of

the production of the G−AIRMET but provided in a

time smear for a 6hr valid period. G−AIRMETs

provide a higher forecast resolution than text

AIRMET products. Since G−AIRMETs and text

AIRMETs are created from the same forecast

“production” process, there exists perfect consisten-

cy between the two. Using the two together will

provide clarity of the area impacted by the weather

hazard and improve situational awareness and

decision making.
Interpolation of time periods between G−AIRMET

valid times: Users must keep in mind when using the

G−AIRMET that if a 00 hour forecast shows no

significant weather and a 03 hour forecast shows

hazardous weather, they must assume a change is

occurring during the period between the two

forecasts. It should be taken into consideration that

the hazardous weather starts immediately after the 00

hour forecast unless there is a defined initiation or

ending time for the hazardous weather. The same

would apply after the 03 hour forecast. The user

should assume the hazardous weather condition

is occurring between the snap shots unless informed

otherwise. For example, if a 00 hour forecast shows

no hazard, a 03 hour forecast shows the presence of

hazardous weather, and a 06 hour forecast shows no

hazard, the user should assume the hazard exists from

the 0001 hour to the 0559 hour time period.