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AIM

10/12/17

7

−1−13

Meteorology

e. SIGMET Outside the  CONUS

1.

Three NWS offices have been designated by

ICAO as Meteorological Watch Offices (MWOs).
These offices are responsible for issuing SIGMETs
for designated areas outside the CONUS that include
Alaska, Hawaii, portions of the Atlantic and Pacific
Oceans, and the Gulf of Mexico.

2.

The offices which issue international SIG-

METs are:

(a)

The AWC in Kansas City, Missouri.

(b)

The AAWU in Anchorage, Alaska.

(c)

The WFO in Honolulu, Hawaii.

3.

SIGMETs for outside the CONUS are issued

for 6 hours for volcanic ash clouds, 6 hours for
tropical cyclones (e.g. hurricanes and tropical
storms), and 4 hours for all other events. Like the
CONUS SIGMETs, SIGMETs for outside the
CONUS 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:

(a)

Thunderstorms occurring in lines, embed-

ded in clouds, or in large areas producing tornadoes
or large hail.

(b)

Tropical cyclones.

(c)

Severe icing.

(d)

Severe or extreme turbulence.

(e)

Dust storms and sandstorms lowering

visibilities to less than 3 miles.

(f)

Volcanic ash.

EXAMPLE

Example of SIGMET Outside the U.S.:
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

f. AIRMET

1.

AIRMETs (WAs) are advisories of signifi-

cant 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
information is available in two formats: text bulletins
(WA) and graphics (G

−AIRMET). Both formats meet

the criteria of paragraph 7

−1−3i and are issued on a

scheduled basis every 6 hours beginning at
0245 UTC. Unscheduled updates and corrections are
issued as necessary. AIRMETs contain details about
IFR, extensive mountain obscuration, turbulence,
strong surface winds, icing, and freezing levels.

2.

There are three AIRMETs: Sierra, Tango,

and Zulu. After the first issuance each day, scheduled
or unscheduled bulletins are numbered sequentially
for easier identification.

(a)

AIRMET Sierra describes IFR conditions

and/or extensive mountain obscurations.

(b)

AIRMET Tango describes moderate

turbulence, sustained surface winds of 30 knots or
greater, and/or nonconvective low

−level wind shear.

(c)

AIRMET Zulu describes moderate icing

and provides freezing level heights.

EXAMPLE

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