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The METAR is a report giving the actual weather conditions at an aerodrome at the time of the report. METAR's are issued every 30 minutes or 1 hour during the opening hours of the aerodrome.
METAR
1. It is a Routine and Current Weather report issued every half an hour by the met office to be disseminated to aircraft. In plain language it is called Meteorological Report and in coded language it is called a METAR.
2. The Meteorology report contains the following elements.
1. Station name
2. Time and date
3. Wind direction and speed
4. Visibility
5. Present weather
6. Amount of significant cloud layer with its base height
7. Temperature and Dew point
8. QNH
9. Trend forecast or Landing forecast
0. Station name is given in ICAO 4 letter code
0. Date and time in UTC at which METAR is issued is mentioned in 6 digits forma
0. Surface Wind:-
• Direction and Speed are reported as: 27010 KT/MPS/KMH
• Variable wind is reported if 3KT or less For example: VRB02KT
Stronger wind if direction changed 180◦ or more: For example VRB10KT
• Calm wind (less than 1 kt) is reported as: 00000KT
• Gusty Wind 32010 gusting 20 is reported as 30020G40KT
• Extreme directions are reported if variation is
60◦ to 180◦ and wind less than 3KT e.g.: 270V050
• Wind less than 100 KT eg 240100 KT is reported as : 240P99KT
0. Visibility is reported in meters or Statute miles
When visibility drops to less than 1500m, then RVR is reported if the Transmissiometer is available.
Visibility is reported as 9999 when it is 10 km or more
0. Weather
. Weather is identified by one or more two letter groups. The full list is not very long so I shall include them all here - even the more obscure phenomena
DZ Drizzle
RA Rain
SN Snow
GR Hail
SQ Squalls
GS Small Hail
SG Snow Grains
PE ICE Pellets
BR Mist
FG Fog
FU Smoke
HZ Haze
VA Volcanic Ash
DU Widespread dust
SA Sand
SS Sandstorm
DS Duststorm
9. We may also describe these in more detail with a two letter prefix.
MI Shallow BC Patches DR Drifting
Slight or heavy conditions may also be described by using a - or + sign before the two letter code. Examples of some combinations:
RA = Rain SHRA = Rain Showers FZFG = Freezing fog
DZ= Slight Drizzle
SHSN = Heavy snow showers MIFG = shallow fog
CB= Cumulonimbus
TCU = Towering CB
0. Clouds
Only three layers of cloud can be reported under the terminology of FEW, SCT, BKN and OVC. When a CB is present it can be reported as the 4th layer i.e. whenever a CB is present.
FEW - 1-2 oktas
SCT - 3-4 oktas
BKN - 5-7 oktas
OVC - 8 oktas
After the wind if term CAVOK is used if:-
1. Visibility is 10 km or more
2. No cloud below 1500 metres (5000 ft.)
3. No weather
Temperature involving 0.5◦C are rounded up to next higher value e.g + 2.5◦ C reported as 3◦ C and - 2.5◦C as MO2◦ C.
0. For QNH and the decimal rounding off is done to the lower full integer. (e.g. 1000.6 is rounded of to 1000)
0. Landing Forecast
1. A landing forecast is called a Trend forecast. It is appended to the end of a meteorological message. It has a validity period of 2 hours. When some significant change is expected from the current conditions in respect to wind, visibility, cloud and weather the same is indicated in the Trend forecast.
2. The Criteria for significant change is more or less like that for SPECI conditions. When no significant change is expected, the term NOSIG is used.