Weather

3D clouds in PLIB version as seen from a EC135.

FlightGear has an impresive weather system, including real weather fetch, 3D clouds and lightning.

METAR

A METAR is a codified observation message indicating an airfield weather conditions observed at a given time. There are different ways of messaging weather reports, but in FlightGear is METAR used.

The METAR-message can be found acros the menu (Weather > Weather Scenario). To have the actual weather (or playing with ATC) you need to enable the Real weather fetch in the FlightGear Wizard.

Such a message is established every hour.

Explanation

Example:

2008/03/15 12:24	KSFO	151224Z	05012KT	10SM	SN	BKN050	02/M08	A3016	RMK AO2 SLP228	T00221083
1	2	3	4	5	6	7	8	9	10	11

1. Date
2. ICAO Identifier (4-letter)
3. Issuance Time DDHHMMz (UTC)
   • COR (CCD in Canada) if correction to observation
4. Wind
   • First 3 digits: True Wind direction or average if variable (VRB).
     • Note: If the wind direction varies 60° or more, the direction will be indicated with a V (e.g. 180V250)
   • Next 2 digits: Mean speed and units
     • KT=knots, KMH=kilometers/hour, MPS=meters/second
   • G (gust) as needed – 2 or 3 digit maximum speed
   • Calm will be indicated by 00000KT
   • Example: 18012G22KT 150V240
5. Horizontal Visibility
   • Prevailing Visibility (PV)
     • Statue miles (SM) and fractions (US & Canada only) or,
     • 4 digit minimum visibility in meters, and,
     • Lowest value and direction, as required (shown as a remark)
   • Runway Visual Range (RVR)
     • R: Runway Designator, L/R/C as needed, “/”
     • P/M: Plus/Minus (US only)
     • 4 digit value (feet/meters)
     • V (variability) with tendency U/D/N (up/down/no change)
     • Example: R18R/1200FTV/U
6. Present Weather (Constructed sequentially):
   • Intensity
   • Descriptor
   • Precipitation (Dominant type is listed first if more than one type reported)
   • Obscuration
   • Other
7. Sky Cover
   • Cloud Description
     • Amount in eights (octas)
     • SKC=Sky Clear (clear below 12,000 for ASOS/AWOS)
     • NSC=No significant clouds
     • FEW=Few (1/8 to 2/8 sky cover)
     • SCT=Scattered (3/8 to 4/8 sky cover)
     • BKN=Broken (5/8 to 7/8 sky cover)
     • OVC=Overcast (8/8 sky cover)
8. Terperature/Dewpoint (whole °C) (preceded by M=minus)
   • First 2 digits = temperature
   • Second 2 digits = dewpoint
9. Altimeter setting (QNH) and indicator (A=InHg, Q=hPa)
10. Supplementary Information
    • RE = Recent weather followed by weather codes
    • WS = Windshear, followed by:
      • TKOF/LDG (takeoff/landing)
      • RWY (2 digits runway identifier and designator L/R/C)
    • RMK = Remark
      • SLP = Sea Level Pressure
      • T00221083 (Expanded temp/dewpoint)
      • 1st, 5th digits: 0=plus, 1=minus
      • 2nd-4th digits: temp (decimal missing) (02.2)
      • 6th-8th digits: dewpoint (decimal missing) (-8.3)
11. Trend Forecast (2 hours from time of observation) (Not used in US)
    • PROB and 2 digits (30 or 40) = probability 30% or 40%
    • Used to indicate the probability of occurance of alternate element(s) or temporary fluctuations
    • Change Indicator
      • BECMG = Becoming (used where changes are expected to reach or pass through specified values
      • TEMPO = Temporary (fluctuations of less than one hour duration
      • NOSIG = No significant change
    • Forecast Wind (same as item 4)
    • Forecast Visibility (as item 5) (9999 indicates 10Kilometers vis or greater)
    • Forecast Weather (as item 6)
    • Forecast Cloud (as item 7)

TAF

An Aerodrome Forecast (TAF) is a concise statement of the expected meteorological conditions at an airport during a specified period (usually 24 hours).

Reading TAF