(d) Hail greater than or equal to $^{3}$/$_{4}$ inch in diameter. 

3. SIGMETs are identified by an alphabetic designator from November through Yankee exclud- ing 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 first issuance of a SIGMET will be labeled as UWS (Urgent Weather SIGMET). Subsequent issuances are at the forecaster’s discre- tion. Issuance for the same phenomenon will be sequentially numbered, using the original designator until the phenomenon ends. For example, the first issuance in the Chicago (CHI) FA area for phenomenon moving from the Salt Lake City (SLC) FA area will be SIGMET Papa 3, if the previous two issuances, Papa 1 and Papa 2, had been in the SLC FA area. Note that no two different phenomena across the country can have the same alphabetic designator at the same time. 

## EXAMPLE − 

## Example of a SIGMET: 

BOSR WS 050600 SIGMET ROMEO 2 VALID UNTIL 051000 ME NH VT FROM CAR TO YSJ TO CON TO MPV TO CAR OCNL SEV TURB BLW 080 EXP DUE TO STG NWLY FLOW. CONDS CONTG BYD 1000Z. 

1. Convective SIGMETs are issued in the conterminous U.S. for any of the following: 

(1) Surface winds greater than or equal to 50 knots. 

(2) Hail at the surface greater than or equal to $^{3}$/$_{4}$ inches in diameter. 

(b) Lines of thunderstorms. 

(c) Embedded thunderstorms. 

## d. Convective SIGMET (WST) 

(a) Severe thunderstorm due to: 

(3) Tornadoes. 

(b) Embedded thunderstorms. 

(d) Thunderstorms producing precipitation greater than or equal to heavy precipitation affecting 40 percent or more of an area at least 3,000 square miles. 

2. Any convective SIGMET implies severe or greater turbulence, severe icing, and low − level wind shear. A convective SIGMET may be issued for any convective situation that the forecaster feels is hazardous to all categories of aircraft. 

3. Convective SIGMET bulletins are issued for the western (W), central (C), and eastern (E) United States. (Convective SIGMETs are not issued for Alaska or Hawaii.) The areas are separated at 87 and 107 degrees west longitude with sufficient overlap to cover most cases when the phenomenon crosses the 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 − 

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 

(c) A line of thunderstorms. 

