SIGMET Codes: Every Contraction Decoded

SIGMETs are written in a telegraphic shorthand that predates the screens they are read on. A pilot who has not met the contractions cannot read the most consequential weather product there is. Every expansion below is one the wxdecoder parser applies, drawn from FAA Order JO 7340.2 and NWS Directive 10-811.

The hazard phrases

These name what the warning is about. The list is fixed, so the hazard is never ambiguous the way it is in a convective SIGMET, where the storm implies hazards nobody wrote down.

Code	What it means
`SEV TURB`	severe turbulence
`SEV ICE`	severe icing
`SEV ICE (FZRA)`	severe icing caused by freezing rain, the worst airframe icing there is
`EMBD TS`	embedded thunderstorms, buried in other cloud and not visually avoidable
`SEV MTW`	severe mountain wave
`VA CLD`	volcanic ash cloud
`TC`	tropical cyclone
`HVY DS`	heavy dust storm
`HVY SS`	heavy sandstorm

Movement and trend

Read the movement wording rather than assuming. MOV E means heading east, while MOV FROM in some products gives the direction it comes from. Our decoder tracks which form was written instead of guessing, because reversing it puts you on the wrong side of the hazard.

Code	What it means
`MOV`	moving, followed by a direction and speed
`STNR`	stationary
`INTSF`	intensifying
`WKN`	weakening
`NC`	no change expected
`CNL`	cancelled before the valid period ran out

Every contraction the decoder expands

Whole-token expansions, applied only on complete words. Only contractions that actually occur in these products are listed: a general abbreviation dictionary would add ambiguity without adding meaning.

Code	What it means
`ABV`	above
`ACFT`	aircraft
`ACSL`	standing lenticular altocumulus
`AFT`	after
`AGL`	above ground level
`ALF`	aloft
`AND`	and
`AOA`	at or above
`AOB`	at or below
`APCH`	approach
`AREA`	area
`ARND`	around
`BLO`	below
`BLW`	below
`BTN`	between
`CHG`	change
`CIG`	ceiling
`CLD`	cloud
`CONDS`	conditions
`CONTG`	continuing
`CSTL`	coastal
`DMSHG`	diminishing
`DSIPTG`	dissipating
`DVLPG`	developing
`EMBD`	embedded
`EMBDD`	embedded
`EST`	estimated
`EXPD`	expected
`FCST`	forecast
`FROM`	from
`FRQ`	frequent
`FZLVL`	freezing level
`HVY`	heavy
`ICG`	icing
`INTSFYG`	intensifying
`ISOL`	isolated
`ISOLD`	isolated
`LGT`	light
`LLWS`	low-level wind shear
`LTL`	little
`LYR`	layer
`MOD`	moderate
`MOV`	moving
`MOVG`	moving
`MTNS`	mountains
`MTW`	mountain wave
`NMRS`	numerous
`NO`	no
`OBSC`	obscured
`OCNL`	occasional
`OTLK`	outlook
`OVR`	over
`PSBL`	possible
`RPRT`	reported
`RPRTD`	reported
`RPTD`	reported
`SEV`	severe
`SFC`	surface
`SVR`	severe
`TO`	to
`TOPS`	tops
`TS`	thunderstorms
`TSRA`	thunderstorms with rain
`TSSN`	thunderstorms with snow
`TURB`	turbulence
`VCNTY`	vicinity
`VIS`	visibility
`WDLY`	widely
`WKN`	weakening
`WKNG`	weakening
`WTRS`	waters
`XPC`	expect

Frequently asked questions

What is the difference between a SIGMET and an AIRMET?

Severity. An AIRMET warns of conditions hazardous to some aircraft, mainly lighter ones. A SIGMET warns of conditions hazardous to all of them, so no rating or equipment exempts you.

Does MOV E mean moving east or coming from the east?

Moving toward the east. Some products instead write MOV FROM, which reverses it. Read the wording rather than assuming, because getting it backwards puts you on the wrong side of the hazard.

Why do convective SIGMETs not list turbulence and hail?

Because a thunderstorm is assumed to carry severe turbulence, severe icing, shear and hail by definition. Listing them every time would add words and no information, so the storm itself is the warning.

How long is a SIGMET valid?

Four hours as a rule. Volcanic ash and tropical cyclone SIGMETs run six. Convective SIGMETs run only two, because storms build and die far too fast for anything longer to be honest.