colour state
{{Short description|System for showing meteorological conditions}}
{{EngvarB|date=June 2019}}
Colour states is a system used for quickly showing meteorological conditions.{{cite web|url=http://www.caa.co.uk/docs/33/srg_gad_gasil2002_04.pdf|title=Aerodrome Colour States|page=10|website=CAA.co.uk|date=2010-12-24|url-status=dead|archiveurl=https://web.archive.org/web/20120910071820/http://www.caa.co.uk/docs/33/srg_gad_gasil2002_04.pdf|archivedate=2012-09-10}}{{cite web|url=http://www.caa.co.uk/docs/33/ga_srg_09webSSL26.pdf|title=SafetySense :eaflet 26|website=CAA.co.uk|date=2010-12-24|url-status=dead|archiveurl=https://web.archive.org/web/20120910071907/http://www.caa.co.uk/docs/33/ga_srg_09webSSL26.pdf|archivedate=2012-09-10}}
Meteorological colour states are determined by the relevant worst condition from the visibility and significant cloud height. In the US and parts of Europe the lowest significant cloud layer is five or more oktas; in the United Kingdom, Belgium, France and the Netherlands it is three oktas or more.{{cite web|url=http://www.chesapeakesportpilot.com/pages/articles/military_wx_codes.pdf|title=Aircrew Quick Reference to the METAR and TAF Codes|publisher=Department of the Air Force|date=2010-12-24|url-status=dead|archiveurl=https://web.archive.org/web/20110708142121/http://www.chesapeakesportpilot.com/pages/articles/military_wx_codes.pdf|archivedate=2011-07-08}} 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.{{Citation needed|date=August 2015}}
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).{{cite web |url=http://www.airlinedispatch.com/dispatch/milcol.html |title=Military color code |website=AirlineDispatch.com |date=2010-12-24 |url-status=dead |archiveurl=https://web.archive.org/web/20100613163946/http://www.airlinedispatch.com/dispatch/milcol.html |archivedate=2010-06-13 }}
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.{{Citation needed|date=August 2015}}
Criteria
The following criteria are used to determine the colour state:{{cite web|url=http://www.skystef.be/metar-decoder.htm |title=METAR Decoder|website=SkyStef.be|date=2010-12-24}}
| class="wikitable" | |||||||
| Colour state | BLU | WHT | GRN | YLO1 | YLO2 | AMB | RED |
|---|---|---|---|---|---|---|---|
| Cloud height in feet
| style="background-color: dodgerblue; color: white" | 2500 | style="background-color: white" | 1500 | style="background-color: limegreen; color: white" | 700 | style="background-color: yellow" | 500 | style="background-color: yellow" |300 | style="background-color: orange" | 200 | style="background-color: red; color: white" | <200 | |||||||
| Visibility in metres
| style="background-color: dodgerblue; color: white" | 8000 | style="background-color: white" | 5000 | style="background-color: limegreen; color: white" | 3700 | style="background-color: yellow" | 2500 | style="background-color: yellow" | 1600 | style="background-color: orange" | 800 | style="background-color: red; color: white" | <800 |