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SIGNIFICANT - DESCRIPTION 17:41 28.05.2012

 
Area forecast in a map format issued for Poland’s territory from the ground level to FL100 and to FL150 in mountain regions (SFC-700 hPa), low level (low-level SIGWX) – SWC is issued by forecasters in Central Aeronautical Forecasting Office-Meteorological Watch Office for general aviation. SWC is a general weather forecast and contains information on significant weather phenomena for aviation.

SWC forecast availability and validity (time given in UTC)
Availability Validity
02.00 06.00 ( 03-09 )
08.00 12.00 ( 09-15 )
14.00 18.00 ( 15- 21 )
20.00 00.00 ( 21-03 )

SFC-FL 100 including the following constant elements:

Height of isotherm 0° written in frames: for example 080 -> 8000 ft -> 2400 m,
SFC -> temperature below 0° from the ground level,
n.SFC -> -> temperature above 0° near the ground level falling below 0° at the ground level,
XXX -> temperature above 0° in the whole layer from SFC to 700hPa,
020/080 -> the height of isotherm 0° 2000ft and 8000ft, in the layer 2000-8000 ft the temperature is above 0°.

Wind speed and direction on FL050 given in knots.
The location of pressure centres is given with its value.

Information on clouds:includes cloud amounts (from FEW to OVC), type of clouds (symbol, for example AS, CU), location of lower and upper boundary given in hundreds of feet above the mean sea level. If a cloud top reaches above FL100, then it is reported as XXX. If the cloud base is above 1500 m and no clouds CB and TCU occur then the abbreviation NSC is used. If the sky condition is clear then the abbreviation SKC is used.

Some additional elements may occur:
fronts – type and its location near the ground,
wind gustsGUSTS given in KT (knots) with the speed more than 30 kt.

Abbreviations used for reporting only TCU and CB clouds: ISOL, OCNL, ENBD, FRQ:
ISOL CB / TCU shall be considered isolated if they consist of individual features which affect, or are forecast to affect, an area with a maximum spatial coverage less than 50 per cent of the area concerned at a fixed time or during the period of validity
OCNL CB / TCU shall be considered occasional if they consist of well-separated features which affect, or are forecast to affect, an area with a maximum spatial coverage between 50 and 75 per cent of the area concerned at a fixed time or during the period of validity
FRQ CB/TCU shall be considered frequent if there is little or no separation between adjacent thunderstorms with a maximum spatial coverage greater than 75 per cent of the area affected, or forecast to be affected by the phenomenon at a fixed time or during the period of validity
EMBD CB/TCU shall be considered embedded if they are embedded within cloud layers and cannot be readily seen due to darkness

Visibility given in kilometres and metres, for example:
10 KM
3-5 KM BR
1500-3000 M DZ
300-500 M FG

Phenomena - given in accordance with METAR code and placed next to visibility (if they occur).

Separated and described areas of different weather types and clouds coverage constitute so called shell line. Inside this line there is an area with worse weather conditions. Sometimes additional terms are used in order to specify its localization for example COT + MAR, MON, etc. Broken line embraces the zone with significant changes of a single weather element. All altitudes are given in hundreds of feet above mean seal level.
 
 
Dictionary of SWC abbreviations.

Abbreviation Meaning Abbreviation Meaning
ABV above AC Altocumulus clouds
AGL above ground level AMSL above mean sea level
AMD amended (map) AS Altostratus clouds
BKN broken BLSN blowing snow
BR mist CB Cumulonimbus clouds
CI Cirrus clouds COT at the coast
CS Cirrostratus clouds CU Cumulus clouds
DZ drizzle EMBD embedded
FEW few FC tornado or waterspout
FL flight level FG fog
FZDZ freezing drizzle FRQ frequent
FZRA freezing dain FZFG freezing fog
GS small hail GR hail
GUSTS UP TO... KT variations from mean wind speed (gusts) HECTOFEET hundreds of feet- altitude indicator
HVY heavy (to indicate the intensity of weather phenomena) HZ haze
ISOL isolated KM kilometres (to indicate visibility)
LCA locally LYR layer or layered
M metres (to indicate visibility) MAR at sea
MOD moderate (to indicate the intensity of weather phenomena) MON above mountains
MTW mountain waves NS Nimbostratus clouds
NSC nil significant clouds N.SFC near the ground
OCNL occasional OVC overcast
PR partly covered area for example with clouds or fog RA rain
RASN rain with snow    
SC Stratocumulus clouds SCT scattered
SEV severe (to indicate the intensity of icing and turbulence) SFC surface
SKC sky condition clear SHRA showers
SHSN showers snow SN snow
SQ squall SQL squall line
ST Stratus clouds TCU towering Cumulus
TDO tornado TS thunderstorm
TSGR thunderstorm with hail TSRA thunderstorm with rain
TSSN thunderstorm with snow VA volcanic ash
VAL in valleys VIS visibility
+ phenomenon intensity- heavy
 
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