SEQUENCE NUMBER
(a) The three-character sequence number should be constructed using a single letter identifying the phenomenon, followed by two numeric characters corresponding to the number of SIGMET issued for that phenomenon for the specified flight information region since 00.01 UTC on the day concerned.
(b) The letters to be used as the first character for the SIGMET sequence number to indicate the specified en-route weather and other phenomena for which the SIGMET has been issued should be:
|
SIGMET
Type |
Specified
en-route phenomena |
Letter
to be used in the sequence number for specified en-route phenomena |
|
WC |
Tropical cyclone |
C |
|
For WC exchange test purposes |
X |
|
|
WV |
Volcanic ash |
A |
|
For WV exchange test purposes |
Y |
|
|
WS |
Thunderstorm |
T |
|
Turbulence |
U |
|
|
Icing |
I |
|
|
Freezing rain |
F |
|
|
Mountain wave |
M |
|
|
Dust storm |
D |
|
|
Sandstorm |
S |
|
|
Radioactive cloud |
R |
|
|
For WS exchange test purposes |
Z |
(c) When SIGMET is issued for test purposes (‘TEST’ status indicator used in the SIGMET), then the appropriate letter for exchange test purposes should be used, i.e. ‘Y’ for a TEST volcanic ash SIGMET. When SIGMET is issued for exercise purposes (‘EXER’ status indicator used in the SIGMET), then the letter chosen should correspond to that used under normal circumstances, i.e. ‘A’ for a SIGMET issued during a volcanic ash exercise.
EASA aviation regulations mandate a specific sequence number format for SIGMETs (Significant Meteorological Information) reports. This number identifies the weather phenomenon (tropical cyclone, volcanic ash, thunderstorm, etc.) using a designated letter, followed by a two-digit count of SIGMETs issued for that phenomenon within the flight information region since the start of the day. Test SIGMETs use specific letters.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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