{{refimprove, date=June 2010
SIGWX is a Significant Weather Chart defined by
ICAO
The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international a ...
.
Weather charts being issued by World Area Forecast Centres (from meteorological offices in London and Washington), presenting the most important meteorological phenomena relevant especially for air traffic transport. WAFC publishes them in two formats
*
BUFR The Binary Universal Form for the Representation of meteorological data (BUFR) is a binary data format maintained by the World Meteorological Organization (WMO). The latest version is BUFR Edition 4. BUFR Edition 3 is also considered current for op ...
code
* PNG images
Charts are typically being issued every six hours (0, 6, 12, 18 UTC). The SIGWX charts only show the forecast for the specific hour, however it is common place for parameters such as the JetStream, CAT & CB to be interpreted +/- 3 hours of the chart validity time. . Prognoses are typically prepared for two ranges of heights:
* SWH - High Level SIGWX (
Flight level
In aviation and aviation meteorology, a flight level (FL) is an aircraft's altitude at standard air pressure, expressed in hundreds of feet. The air pressure is computed assuming an International Standard Atmosphere pressure of 1013.25 hPa ...
250-630)
* SWM - Medium Level SIGWX (
Flight level
In aviation and aviation meteorology, a flight level (FL) is an aircraft's altitude at standard air pressure, expressed in hundreds of feet. The air pressure is computed assuming an International Standard Atmosphere pressure of 1013.25 hPa ...
100-450)
Weather phenomena:
* Cloud - including information about cloud type, height of base and top, turbulence and icing risk
* Clear Air Turbulence - including base and top height, strength of turbulence
* Jet Stream - including base and top height, wind speed
* Tropopause Height
* Tropical Cyclone, Sandstorm
* Volcanoes
* Frontal system
IMPORTANT NOTE: Amendment 74 to
ICAO
The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international a ...
Annex 3 (effective 7 November 2007) Amendment 74 to ICAO Annex 3 /ref> eliminated the requirement for depiction of surface fronts and well-defined convergence zones (e.g. ITCZ) on WAFS SIGWX forecasts (in BUFR-code and PNG chart form). WAFC still publishes frontal bulletins, but they contain no data.