Colour states is a system used for quickly showing
meteorological conditions.
Meteorological colour states are determined by the relevant worst condition from the
visibility
The visibility is the measure of the distance at which an object or light can be clearly discerned. In meteorology it depends on the transparency of the surrounding air and as such, it is unchanging no matter the ambient light level or time of ...
and significant
cloud height
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid drop (liquid), droplets, ice crystals, frozen crystals, or other particulates, particles suspended in the atmosphere of a planetary body or similar space. ...
. In the US and parts of Europe the lowest significant cloud layer is five or more
okta
In meteorology, an okta is a unit of measurement used to describe the amount of cloud cover at any given location such as a weather station. Sky conditions are estimated in terms of how many eighths of the sky are covered in cloud, ranging from ...
s; in the United Kingdom, Belgium, France and the Netherlands it is three oktas or more. If visibility or cloud height measurements fall on a boundary (e.g. 5000 m visibility or 1500 ft cloud height) the colour state assumes the higher value in this case WHT.
If an airfield runway is unusable for reasons other than clouds or low visibility (e.g. ice or other obstructions) then the word BLACK is written in full and placed immediately before the actual colour state (e.g. BLACKWHT).
The colour state may be appended to a
METAR
METAR is a format for reporting weather information. A METAR weather report is predominantly used by aircraft pilots, and by meteorologists, who use aggregated METAR information to assist in weather forecasting.
Raw METAR is the most common form ...
report. A short period forecast called a ''TREND'' which covers the following two hours from the observation may also be added, often with reference to the colour state.
Criteria
The following criteria are used to determine the colour state:
See also
*
Colour code
A color code is a system for displaying information by using different colors.
The earliest examples of color codes in use are for long-distance communication by use of flags, as in semaphore communication. The United Kingdom adopted a color ...
References
{{DEFAULTSORT:Colour State
Meteorological data and networks