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SIGMET

SIGMETA SIGMET is a warning issued to provide urgent advice to aircraft of the actual or expected occurrence, in areas over which meteorological watch is being maintained, of weather

phenomena that are potentially hazardous. A SIGMET will contain information on one of the

following phenomena:

Code Description

OBSC TS Obscured thunderstorms

EMBD TS Embedded thunderstorms

FRQ TS Frequent thunderstorms

SQL TS Squall line thunderstorms

OBSC TSGR Obscured thunderstorms with hail

EMBD TSGR Embedded thunderstorms with hail

FRQ TSGR Frequent thunderstorms with hail

SQL TSGR Squall line thunderstorms with hail

TC Tropical cyclone

SEV TURB Severe turbulence

SEV ICE Severe icing

SEV ICE FZRA Severe icing due to freezing rain

SEV MTW Severe mountain wave

HVY DS Heavy duststorm

HVY SS Heavy sandstorm

VA Volcanic ash

RDOACT CLD Radioactive cloud

A SIGMET will provide information on the location, extent, intensity and expected evolution

of the specified phenomenon.

SIGMETs for thunderstorms are only issued when they are:

• obscured(OBSC)byhazeorsmoke

• embedded(EMBD)withincloudlayers

• frequent(FRQ),i.e.withlittleornoseparationbetweencloudsandcoveringmorethan

75% of the area affected

• squallline(SQL)thunderstormsalongalineofabout100nauticalmilesormoreinlength,

with little or no separation between clouds

SIGMETforthunderstormsdonotincludereferencetocumulonimbuscloud(CB)orassociated icing and turbulence as these are implied as occurring.

Pilots in command of aircraft encountering any phenomenon in this table not notified by SIGMET must report details of the phenomenon in an AIREP SPECIAL

FURTHER INFORMATIONAviation Weather Services

Visit us at www.bom.gov.au

The format given here is valid until 29 May 2013*

*Refer to http://www.bom.gov.au/aviation/data/education/awp-sigmet.pdf for the new format.

SIGMET for tropical cyclones include cumulonimbus but not associated icing and turbulence as these are implied as occurring.

Responsibility for the issuance of SIGMET within the Australian Flight Information RegionsSIGMETsforvolcanicasharetheresponsibilityoftheVolcanicAshAdvisoryCentre,Darwin.

SIGMETsfortropicalcyclonesaretheresponsibilityoftheTropicalCycloneWarningCentresinPerth,DarwinandBrisbane.

SIGMETsforturbulenceandicingaboveFL185aretheresponsibilityoftheAviationWeatherCentre,Melbourne.

SIGMETforallotherphenomenaaretheresponsibilityoftheMeteorologicalWatchOfficeslocatedinPerth,Darwin,Adelaide,Hobart,Melbourne,SydneyandBrisbane.

SIGMET Structure

Bulletin Identification• WCAU01forSIGMETfortropicalcyclones

• WVAU01forSIGMETforvolcanicashcloud

• WSAU21forSIGMETforotherphenomena

Originating Office (WMO Location Indicator)TheWorldMeteorologicalOrganisation(WMO)locationindicatorsforAustralianMeteorologicalWatchOfficesare:

APRM Adelaide

APRF Perth

ABRF Brisbane

ASRF Sydney

ADRM Darwin

AMRF Melbourne

AMHF Hobart

AMMC AviationWeatherCentreMelbourne

Note:ThesedifferfromtheICAOindicators(beginningwithY)usedelsewhereinthemessage.

WSAU21AMMC180357

YMMMSIGMETMM01VALID

180439/180839YMMC-

YMMMMELBOURNEFIRSEV

TURBFCSTWIS3200E12800-

S3200E13000-S4700E13600

-S4700E13400FL260/400

MOVE25KTNC

STS:NEW

WVAU01ADRM200100

YBBBSIGMETBT04VALID

200100/200700YPDM-

YBBBBRISBANEFIRVA

ERUPTIONLOCS0416E15212

VACLDOBSAT200100Z

A100/180APRX120NMBY

40NMS1130E14530-S1330

E14900-S1030E15030

-S0830E14700-S1130

E14430MOVSW20KTFCST

0700ZVACLDAPRXS110

E144530-S1230E14930

-S1050E15130-S0800

E14700-S1130E14400

STS:REVSIGMETBT03

191900/200100

WCAU01APRF180217

YMMMSIGMETPH01VALID

180215/180815YPRF-

YMMMMELBOURNEFIRTC

ILSAOBSAT0000ZS1330

E11324CBTOPFL500WI

120NMOF

CENTREMOVWSW17KT

INTSFFCST0815ZTCCENTRE

S1418E11036

STS:NEW

Issue Date/TimeIssuedate/timeisgiveninUTCintheformDDHHMM,whereDDisdayofmonth,andHHMMistimeinhoursandminutes.

Flight Information RegionGivestheabbreviationfortheFIR(YMMMorYBBB)inwhichthephenomenonislocated.

IdentifierThe message identifier is SIGMET.

Daily Sequence NumberThefour-charactersequencenumberconsistsof:

• atwo-letterdesignatortoindicatethegenerallocationoftheevent(asgiveninthetwo

mapsbelow),and

• atwo-digitnumber,givingthesequencenumberofSIGMETsissuedbytherelevantoffice,

withinthegivenFIR(BrisbaneorMelbourne)since0000UTC.

Thetwo-letterdesignators,andtheirassociatedgeographicalextent,forlow-level(belowFL185)SIGMETincludingtropicalcyclonesare:

Thetwo-letterdesignators,andtheirgeneralassociatedgeographicalextent,forvolcanicashandhigh-level(aboveFL185)icingandturbulenceSIGMETare:

A Altitude

ABV Above

APRX Approximately

BLW Below

CLD Cloud

CNL Cancel

DS Dust storm

E East or eastern longitude

EMBD Embedded

FCST Forecast

FIR Flight Information Region

FL Flight level

FRQ Frequent

FZRA Freezing rain

GR Hail

HVY Heavy

ICE Icing

INTSF Intensifying

KT Knots

LOC Location

MOV Moving

MT Mount

N North or northern latitude

NC No Change (in intensity)

NM Nautical Miles

OBS Observed

OBSC Obscured

RDOACT CLD

Radioactive cloud

REV Review

S South or southern latitude

SEV Severe

SQL Squall line

SS Sand storm

STNR Stationary

STS Status

TC Tropical cyclone

TOP Cloud Top

TS Thunderstorm

TURB Turbulence

VA Volcanic ash

W West or western longitude

WI Within (area)

WKN Weakening (intensity)

Z Code for UTC (Universal Time Coordinated)

SIGMET Abbreviations

MELBOURNE FIR

BRISBANE FIR

PH

BN

AD

ML

DN

SY

HB

160°E

160°E

150°E

150°E

140°E

140°E

130°E

130°E

120°E

120°E

110°E

110°E

100°E

100°E

90°E

90°E

80°E

80°E0° 0°

10°S 10°S

20°S 20°S

30°S 30°S

40°S 40°S

50°S 50°S

Originating Office (ICAO Location Indicator)TheInternationalCivilAviationOrganization(ICAO)locationindicatorsforAustralianMeteorologicalWatchOfficesare:

YPRM Adelaide

YPRM Perth

YBRF Brisbane

YSRF Sydney

YPDM Darwin

YMRF Melbourne

YMHF Hobart

YMMC AviationWeatherCentreMelbourne

Flight Information RegionThisgivestheabbreviationandfullnamefortheFIRinwhichthephenomenonislocated.

Meteorological InformationThis section includes:

• typeofphenomenon

• observedorforecast

• location,bothhorizontalandverticalextent

• movementorexpectedmovement

• expectedchangeinintensity

• forecastpositionattheendofthevalidityperiod(onlyinSIGMETforTCandVA)

The first point of a polygon is not repeated when describing the horizontal extent of an event.

SIGMETfortropicalcyclonesdonotincludereferencetocumulonimbuscloud(CB)orassociated icing and turbulence as these are implied as occurring.

Cancel SIGMETIf during the validity period of a SIGMET, the phenomenon for which the SIGMET is no longer occurring or is no longer expected, the SIGMET is cancelled by issuing a SIGMET with theabbreviationCNLinlieuofmeteorologicalinformation.CNLisalsoincludedonthestatus line.

SIGMET StatusThe status line indicates whether the SIGMET is:

• NEW-theSIGMETisforanewphenomenon.

• REV-theSIGMETreviewsanearlierSIGMETforthephenomenon.

• CNL-theSIGMETcancelsacurrentSIGMET.

WSAU21AMMC180720

YMMMSIGMETMM02VALID

180720/180839YMMC-

YMMMMELBOURNE

FIRCNLSIGMETMM01

180439/180839

STS:CNLSIGMETMM01

180439/180839

Airservices Australia is the official distributor of aviation forecasts, warnings and observations issued by the Bureau of Meteorology. Airservices’ flight briefing services are available at www.airservicesaustralia.com. Telephone contact details for elaborative briefings are contained in Airservices’ Aeronautical Information Publication Australia (AIP), which is available online through their website.

Other brochures produced by the Bureau of Meteorology’s aviation weather services program can be

found at www.bom.gov.au/aviation/knowledge-centre.

© CommonwealthofAustralia,17May2012