METAR : Actual weather reports issued every 30 mint, In Saudi Arabia every hour.

TAF   : Terminal Area Forecast
            FC- Short rang forecast issued every 3 hours and valid for 9 hours.
         FT- Long rang forecast issued every 6 hours and valid for either 12, 18, or 24 hours.

SPECI : Special Weather Report.
             The actual weather change significantly between the times METARs are published.

SIGMENT : Information issued by a meteorological watch office concerning the occurrence or expected occurrence
              of specified en-route weather phenomena which may affect the safety of aircraft operation.
              Sigment validity should be not more than 6 hours, and preferably not more than 4 hours.

AERODROME WARNING : Meteorological condition which could adversely affect aircraft on ground, aerodrome
                                             facilities and services.
                                             Example : Thunderstorm, sand or dust storm, strong surface wind, hail, raising sand
                                                             or dust and squall.

TEMPO : Temporary fluctuations in the meteorological condition which reach or pass specified values and last for
                a period of less than 1 hour in each instance and, in the aggregate, cover less than one-half of the period
                during which the fluctuations are forecast to occur.

BECMG : The meteorological condition are expected to reach or pass through specified values at regular or irregular rate.

PROGNOSTIC CHART : A chart of expected or forecast conditions.

SYNOPTIC CHART : A chart, such as the familiar weather map, which depicts the distribution of meteorological
                                  condition over an area at a given time.

JET STREAM : The jet stream typically occurs in a break in the tropopause  ( the tropopause is not continuous
                         but generally descends step-wise from the Equator to the poles. These steps occur as a "breaks")
                         The concentrated winds, must be 50 knots or greater to classify as jet stream.
                         The jet maximum is not constant : LONG - 1000 - 3000 miles
                                                                           HEIGHT - 3000 - 7000 ft
                                                                           WIDTH - 100 - 400 miles

CAT : Clear air turbulence is a high level wind shear turblence.
          CAT is most pronounced in winter when temperature contrast is greatest between cold, and warm air.
          Strong winds may carry a turbulent air away from its source region.

          If you caught in CAT near a jet stream you should climb or descend a few thousand feet or you, could
          move farther from the jet core.

DRIZZLE : A form of precipitation. Very small water drops that appear to float with the air currents while falling
                  in an irregular path.

HAZE : Fine dust or salt particles dispersed through a portion of the atmosphere; particles are so small they cannot
            be felt or individually seen with the naked eye, but diminish the visibility; distinguished from fog by its bulish
            yellowish tinge.

SHOWER : Precipitation from a cumuliform cloud; characterized by the suddenness of beginning and ending by
                  raped change of intensity, and usually by rapid change in the appearance of the sky.

SMOG : Amixture of smoke and fog.

ST. ELMOs FIRE : A luminous brush discharge of electricity from protruding objects, such as mast, aircraft,
                              lightning rods, etc., occurring in stormy weather.

VIRGA : Water or ice particles falling from a cloud, usually in streak, and evaporating before reaching the ground.

ISOBAR : A line of equal or constant barometric pressure.

ISOTACH : A line of equal or constant wind speed.

ISOTHERM :A line of equal or constant temperature.

TROPOSPHERE : That portion of the atmosphere from earth's surface to the tropopause; that is, the lowest
                             10 to 20 kms of the atmosphere . the troposphere is characterized by decreasing temp, with height,
                             and by appreciable water vapor.

STARTOSPHERE : The atmospheric layer above the tropopause, average altitude of base and top, 7 and 22 miles
                               respectively; characterized by a slight average increase of temp. from base to top and is very
                               stable; also characterized by low moisture content and absence of clouds.

TROPOPAUSE : The tropopause is a thin layer forming the boundary between the troposphere and stratosphere.
                           Height of the tropopause varies from a bout 65,000 feet over the Equator to 20,000 feet or
                           lower over the poles.

                           Temperature and wind vary greatly in the vicinity of the tropopause affecting efficiency, comfort,
                            and safety of flight.

Weather Abbreviations  . Symbols for significant weather      .Front and other symbols used    Clouds

DESCRIPTORS:

BC      Patches                                                  PR            Partial
BL      Blowing                                                 MI             Shallow
DR     Drifting                                                  RE             Recent
FZ      Supercooled                                           TS             Thunderstorm
                                                                       VC             In the Vicinity

BOUNDARIES

  Symbols for significant weather  Front and other symbols used     Definitions Clouds

Thunderstorm	Drizzle
Tropical cyclone	Rain
Sever line squall*	Snow
Moderate turbulence	Shower
Severe turbulence snow	Widespread blowing
Mountain waves haze	Sever sand or dust
Slight aircraft icing	Widespread sand storm or dust storm
Moderate aircraft icing	Widespread haze
Sever aircraft icing	Widespread mist
Widespread fog	Widespread smoke
Hail	Freezing precipitation**

*     In flight documentation for flights operating up to FL 100, this symbol refers to "line squall".
**   This Symbol does not refer to iscing due o precipitation coming into contact with an aircraft which is at very low temperature.
Note - Height indications between which phenomena are expected, top above base, as per chart legend.

Weather Abbreviations  .  Front and other symbols used   .  Definitions .     Clouds

Cold front at the surface	Tropopause level
Warm front at the surface	Position, speed and level of max. wind
Occluded front at the surface	Convergence line
Quasi-stationary front at the serface	Freezing level
Tropopause High	Intertropical Convergence zone
Tropopause Low

The double bar denotes changes of level by 3000ft or less and/or wind speeds by 37 km/h-20 kt.  In the example, at the double bar the wind speed is 225 km/h-120kt. The heavy line delineating the jet axis begins/ends at the points where a wind speed of 150km/h-80kt is forecast.

Weather Abbreviations  Symbols for significant weatherDefinitions   Clouds

CI    =   Cirrus                    AS     =  Altostratus                              ST  =  Stratus
CC   =  Cirrocumulus             NS     =  Nimbostratus                         CU  =  Cumulus
CS   =   Cirrostratus            SC     =   Stratocumulus                       CB   =  Cumulonimbus
AC  =    Altocumulus           TCU  =   Towering Cumulus

Amount :

                 Clouds except CB          SKC =  sky clear          ( 0/8 )           octs
                                                         FEW =  few amount     ( 1/8  to 2/8 ) octs
                                                         SCT  =  scattered         ( 3/8  to 4/8 ) octs
                                                         BKN =  broken            ( 5/8  to 7/8 ) octs
                                                         OVC =  overcast          ( 8/8 )            octs

CB only :
                                                        ISOL     =   Individual CBs  (Isolated)
                                                        OCNL   =   Well sparated CBs (occasional)
                                                        FRQ      =   CBs with little or no separation ( frequent)
                                                        EMBD   =   CBs embedded in layers of other clouds or concealed by haze ( embedded)

HEIGHTS :
                          Heights are indicated on SWH and SWM charts in flight levels (FL), top over base . When XXX is used, tops or bases are
                          outside the layer of the atmosphere to which the chart applies.

                         In SWL charts :
                                                 1) Heights are indicated as altitudes above mean sea level
                                                 2) the abbreviation SFC is used to indicate ground level
 

Weather Abbreviations  . Symbols for significant weather      .Front and other symbols used .   Definitions

 

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