Colour state

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Meteosat 8 IR satellite Image with weather colour states superimposed, taken 0900 UTC 15 October 2006. Anticyclone over Europe led to settled conditions with areas mist and fog, as indicated by the AMB and RED colour states.

Colour States are a system used for quickly showing meteorological conditions.

Meteorological colour states are determined by the relevant worst condition from the visibility and significant cloud height. In the USA and parts of Europe the lowest significant cloud layer is 5 oktas or more; in the United Kingdom it is three oktas or more. If visibility or cloud height measurements fall on a boundary (e.g 1500 ft or 5000 m) 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 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.

[edit] Colour state criteria