AIM 

6/17/21 

boundaries. Bulletins are issued hourly at H+55. 
Special bulletins are issued at any time as required 
and updated at H+55. If no criteria meeting 
convective SIGMET requirements are observed or 
forecasted, the message “CONVECTIVE SIGMET... 
NONE” will be issued for each area at H+55. 
Individual convective SIGMETs for each area (W, C, 
E) are numbered sequentially from number one each 
day, beginning at 00Z. A convective SIGMET for a 
continuing phenomenon will be reissued every hour 
at H+55 with a new number. The text of the bulletin 
consists of either an observation and a forecast or just 
a forecast. The forecast is valid for up to 2 hours. 

EXAMPLE

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CONVECTIVE SIGMET 44C 

VALID UNTIL 1455Z 

AR TX OK 

FROM 40NE ADM-40ESE MLC-10W TXK-50WNW 

LFK-40ENE SJT-40NE ADM 

AREA TS MOV FROM 26025KT. TOPS ABV FL450. 

OUTLOOK VALID 061455-061855 

FROM 60WSW OKC-MLC-40N TXK-40WSW 

IGB-VUZ-MGM-HRV-60S BTR-40N 

IAH-60SW SJT-40ENE LBB-60WSW OKC 

WST ISSUANCES EXPD. REFER TO MOST RECENT 

ACUS01 KWNS FROM STORM PREDICTION CENTER 

FOR SYNOPSIS AND METEOROLOGICAL DETAILS 

FIG 7

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1

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4 

SIGMET and AIRMET Locations 

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 Conterminous United States 

7

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1

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12 

Meteorology