K
Thunderstorm
:
Widespread Fog
Ç
Tropical Cyclone
@
Radioactivematerialsin the atmosphere t2)
aj\
Volcanic Eruptiontr)
,-\j'
Sevefe Squall Line (1)
\
SevereSandor DustHaze
À\
MountainObscuration
4
Moderate Turbulence
|-
Widespread Sandstormor DustStorm
oo
Widespread Haze
-^-
SevereTurbulence
Drizzle
+
Widespread BlowingSnow
O
MountainWaves
iii iii
Rain
l-
WidespçeadSmoke
\H.'
ModerateAircraft lcing
*
Snow
/av
Freezing Precipitation(4)
\Ht,
SevereAircraftlcing
V
Shower
-ô,-^-
Cold Front at the Surface
--------.--
WarmFrontat the Surface
-^--^â
Occluded Front at the Surface
,
Movement of a frontal system
t{ 'x'--
r0
Movementof a pressuresystem
A
Widespread Mist
Hail
High Tropopause
Ê
TropopauseLow
@
State of the Sea
Tropopause tevef
t=sôl
Quasi-stationaryFrontatthe + ^^\
*
:
,,*
< tô' :1oo-l
@
speedand levelof max'
@
;TT'on' convergence line
sea-surfaceTemperature
wi:::t**
surrace strong
Area of SignifrcantWeather
Freezinglevet
lrrr
CAT-area
| 018
* thissymbolrefersto widespreadsurtace wind speedsexceeding60 km/h(30 kt).
FL 32O 220.t44J{)
Wind arrows indicatethe maximumwind in jet and the flight level at which it occurs. lf the maximumwind speed is 225 km/h (120 kq or more,the flight levels betweenwhich winds are greaterthan 150 km/h (80 kt) is placed below the maximumwind level. In the example,winds are greaterthan 150 km/h (80 kt) between FL 220 and FL 400. The heavy line delineatingthe jet axis begins/endsat the pointswhere a wind speed of 150 km/h (80 kt) is forecast. Significantchanges(speed of 20 knots or more, 3000 ft (less if practicable)in flight level) are marked by the double bar. In the example,at the double bar the wind speedis225kmlh (120 k0.
Models SWH and SWM - Significant Weather Charts (high and medium)
Model SWL - Significânt Weather Charts (low level)
= demarcationof areas of significantweather = delineationof area of CAT = Positionof jet stream axis with indicationof wind direction, speed in kt or km/h and height in flight levels.The verticâl extentof the jet stream is indicated(in flight levels)e.g. FL 270 accompaniedby 2401290indicatesthat the jet extendsfrom FL 240 to FL 290. Figures on arrows = speed in kt or km/h of movementof frontal system Direction of arrows = directionof movementof frontal system = height in flight levels of tropopauseal spot locationseg Flight levels Low and High points ofthe tropopausetopographyare _ inside small indicatedby the letters L or H respectivelyinside rectangles l34ol a pentagonwith the height in flight levels.
x
Scalloped line Heavy broken line Heavy solid line interrupted by wind arrow and flight level
= = = = =
positionof pressurecentres given in hectopascals centre of low oressure centre of high pressure demarcationofareaofsignificantweather altitude of 0'C isothermin feet (hectofeet)or metres NOTE: O.jClevel may als be indicatedby lôiooo;l i.e. 0"C level is at an altitude of 6.000 fr. Figures on arrows = Speed in kt or km/h of movementof frontal systems, depressionsor anticyclones Direction of arrows = directionof movementof frontal systems, depressionsor anticyclonès Figure inside the state of the sea symbol = total wave height in feet or metres "C Figure inside the sea-surface temperature symbol = sea-surfacetemperaturein Figures inside the strong surface wind symbol = wind in kt or km/h L H Scallopedlines Dashed lines
Abbreviations Type Cl = Cirrus CC = Cirrocumulus CS = Cirrostratus AC = Altocumulus
AS NS SC ST
Phenomena for which Sigmets are issued
used to describe clouds = Altostratus = Nimbostratus = Stratocumulus = Stratus
At cruising levels: - Thunderstorm (OBSC,EMBD,SQL, FROI - TS - Thunderstorm with hail- TSGR - Tropicalcyclone- TC (+ cyclonename) - SevereTurbulence- SEV TURB - Severelcing- SEV ICE - Severelcingdue to FreezingRain- SEV ICE (FZRA) - Severemountainwaves- SEV MTW - HeavySandstorm- HVY SS - HeavyDuststorm- HVYDS - VolcanicAsh - VA (+ volcanoname) - Radioactive cloud- RDOACTCLD
CU = Cumulus TCU = ToweringCumulus CB = Cumulonimbus
Amount Clouds exceqt CB = sky clear(0/B) SKC = few(1/Bto2/8) FEW = scatteredi3/8 to 418) SCT = broken lslb to zlal BKN = overcasi (818) ovc CB onlY = individualCBs (isolated) ISOL = well-separated CBs (occasional) OCNL = CBs with little or no separation(frequent) FRQ = cBs embeddedin layersof other,cloudsor concealedby haze {embedded) EMBD
OBSC = TSs obscuredby hazeor smokeor not visibledue to darkness(obscured) EMBD = TSs embeddedin layerso{ otherclouds (embedded) SOL = TSs alonga linewith littleor no separation(squallline) FRO = TSs or CBs with littleor no separation (frequent)
Heights Heiàntsare indicatedon SWH and SWM chartsin flightlevels(FL),top over base. the WhËnXXX is used,tops or basesare outsidethe layerof the atmosphereto which chartapplies.
inêwï àn"rtt, l.Heightsareindicatedasa|titudesinhectofeetabovemeansea|eve|; SFC is usedto indicategroundlevel: 2. The abbreviation to 3. XXX is used to indicatethat tops are ôuiside the layer of the atnosphere aPPlies. chart whichthe Note: LYR on a SIGWX chart indicateslayer ôf clouds or layeredclouds'
Conversion Formulas
Arrows and Feathers Arrows indicatedirection-Numberof pennantsand/orfeatherscorrespondto speed -^'
knot = 1.852kilometresPerhour knot = 0.514444metresPersecond metreper second= 3.600kilometresper hour foot = 0.3048metres nauticalmile= 1.852kilometres
Pennantscorrespondto 50 kt or 93 km/h Featherscorrespondto 10 kt or 1B km/h Half featherscorrespondto 5 kt oi 9 km/h
Example: ^ ^\r
(equivalentto 213 kmlh) 270"1115kt
Info on atpPer Wind and Il pper-Ai r TemPeratu re Cha rts Arrows and feathers:see above Temperatures:always negativetemperatureexcept when preceededby PS
llnits used in ICAO-Products Parameter
Unit(s)
Wind directionfor landingand take off Wind directionfor all otherpurposes WindSpeed
DegreesMagnetic DegreesTrue Knotsor KilometresPer Hour or Metresper Second Metres or Kilometres Hectofeet(= Flight Levels) Hectofeet Hectopascal DegreesCelcius(=Centigrade) NauticalMilesor Kilometres Knotsor Klometres Per Hour Hectofeet(=Flight Levels) Hoursand MinutesUTC
Visibility CloudHeights VerticalVisibilitY Air Pressure Temperature HorizontalDistances Speedof Movementof Phenomena Level(altitude)of Occurrenceof Phenomena Time
WeatherPhenomena
Qualifier Descriptor (2)
Intensityor Proximity (1) Light No qualifier
Moderate
+
Heavy
VC
ln the vicinity
DusUSand whirls (dustdevils)
Smoke
SQ
Squalls
VA
Volcanicash
FC
lce crystals (diamonddust)
DU
Widespread dust
Funnelcloud(s) (tornadoor waterspout)
ss
Sandstorm
PL
lce pellets
SA
Sand DS
Duststorm
GR
Hail
HZ
Haze
GS
Smallhail and/orsnow pellets
UP
Unidentified precipitation
Shallow
DZ
Drizzle
BR
Mist
BC
Patches
RA
Rain
FG
Fog
PR
Partial(covering S N part of the aerodrome) SG
Snow
FU
Snowgrains
tc
DR
Low drifting
BL
Blowing Shower(s)
TS
Thunderstorm
FZ
Freezing (supercooled)
Other Phenomena (5) PO
MI
SH
CAVOK
Obscuration (4)
Precipitation (3)
CloudAnd VisibilityOK replacesvisibility,presentweatherand cloud informationif: 1. the visibilityis 10 km or more,and 2. there are no CB's and there are no cloudsbelow 1500 m (5000ft) or belowthe highestminimumsectoraltitude, whicheveris greater,and 3. there is no significantweatherto aviation.
NSC
Nil SignificantCloud is used as cloud informationif there are no cloudsof operationalsignificance,i.e. there are no CB's and there are no cloudsbelow '1500m (5000ft) or belowthe highestminimumsectoraltitude,whicheveris greater,and there is no restrictionon verticalvisibility and CAVOKand SKC are not appropriate.
ABV AD AMD
APru( BECMG BLW CAT CLD CNL CTA FCST FIR FM INTSF
Above Aerodrome Amended Approximateor approximately Becoming Below ClearAir Turbulence Cloud Cancelled ControlArea Forecast FlightlnformationRegion From lntensifying
LOC MOV NG NCD NDV NOSIG NSW
oBs OTLK PROB RVVY
sFc srG STNR
Locally Moving No Change No Clouds Detected No DirectionalVariation No SignificantChange Nil SignificantWeather Observed Outlook Probability Runway Surface Significant Stationary
TEMPO TL UIR VIS VRB W WDSPR
wt WID WKN WRNG WS WSPD WX
Temporary Titl Upperflight lnformationRegion Visibility Variable VerticalVisibility Widespread Within width Weakening Warning Wind Shear Wind Speed Weather
