Leerjet 35/36 Developed for Training Purposes 5-33
February 1998
Flight Planning
ICAO Weather Format
On July 1, 1993, the worldwide (ICAO) and North A aerodrome
weather codes merged into a new international for forecasts
and reports. The new codes are the result effort to meet
revised aeronautical requirements and confusion in the aviation
community.
The United States converted to METAR / TAF format on 1996
with terminal aerodrome forecast (TAF) replacing terminal fore-
cast airport and meteorological aviation weather report
(METAR) replacing the airport surface observation (AOS).
Although the aviation community now uses a standard codes,
some differences remain between U.S. and ICAO For example,
the following differences may remain in eff
Horizontal visibility is reported in statute miles (SM)
U.S. code and in meters in the ICAO code. To avoid
confusion, the suffix SM follows the visibility value if
it is reported U.S. code. Additionally, when forecast
visibility in exceeds six statute miles, the prefix P
appears (e.g., a visibility forecast greater than six
statute miles).
Runway visual range (RVR) is reported in feet (FT)
in code and in meters in ICAO code. When RVR is
reported a U.S. runway, the suffix FT is added (e.g.,
R27L/ runway 27 left RVR 2,700 ft). RVR is reported
only weather, not a forecast TAF.
Ceiling and visibility okay (CAVOK) is not used in the
Temperature, turbulence, and icing conditions are
forecast in a U.S. TA F. Turbulence and icing are
forecast Forecasts (FAS). Surface temperatures are
forecast public service and agricultural forecasts.
Trend forecasts are not included in U.S. METARs.
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