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Difference between revisions of "Weather"

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===Explenation===
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===Explanation===
 
This TAF example of a 30-hour TAF, released on November 5 2008 at 1730 UTC:
 
This TAF example of a 30-hour TAF, released on November 5 2008 at 1730 UTC:
  

Revision as of 05:53, 2 June 2009

3D clouds in PLIB version as seen from a EC135.
The Weather Scenario window in FlightGear 1.9.1.
The new Weather Scenario window in FlightGear CVS.

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

In meteorology and aviation, TAF is a format for reporting weather forecast information, particularly as it relates to aviation. "TAF" is an acronym of Terminal Aerodrome Forecast or, in some countries, Terminal Area Forecast. Generally, TAF's can apply to a 9- or 12-hour forecast; some TAFs cover an 18- or 24-hour period; and as of November 5,2008, TAFs for some major airports cover 30 hours periods. The date/time group reflects the new 30 hour period in Coordinated Universal Time (UTC), as always.


Explanation

This TAF example of a 30-hour TAF, released on November 5 2008 at 1730 UTC:

TAF KXYZ 051730Z 0518/0624 31008KT 
     3SM -SHRA BKN020
     FM052300 30006KT 5SM -SHRA OVC030 
     PROB30 0604/0606 VRB20G35KT 1SM 
     TSRA BKN015CB 
     FM 060600 250010KT 4SM -SHRA OVC050
     TEMPO 0608/0611 2SM -SHRA OVC030=  
     RMK NXT FCST BY 00Z=

The first line contains identification and validity times.

  • TAF indicates that the following is a terminal area forecast.
  • KXYZ indicates the airport to which the forecast applies (ICAO airport code).
  • 051730Z indicates that the report was issued at 1730 UTC on the 5th of the month.
  • 0518/0624 indicates that the report is valid from 1800 UTC on the 5th until 2400 UTC on the following day.

The remainder of the first line and the second line contain the initial forecast conditions. Variations of the codes used for various weather conditions are many.

  • 31008KT indicates that the wind will be from 310 degrees at 8 knots.
  • 3SM -SHRA BKN020 indicates that visibility will be 3SM (statute miles) in light (-) showers (SH) of rain (RA), with a broken ceiling (at least 5/8 of the sky covered) at 2,000 feet.

Each line beginning with FM starts a new forecast period.

  • FM052300 indicates the next period lasts from (FM) 2300 UTC on the 5th to 0000 UTC on the 6th.

The remainder of the line has similar formatting to the other forecast lines.

The final line is for errata, comments, and remarks.

  • RMK NXT FCST BY 00Z indicates a remark that the next forecast will be issued by 0000 UTC.

External Links

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