Suppose you’re in the middle of nowhere (or at least anywhere in Greenland) and need to know the coming weather conditions. The typical five day forecast is not gonna cut it.

METAR (METeorological Airport Report) describe the current conditions as observed by the weather tower at an airport. These are reliable, updated frequently, although incredibly terse. Similarly, TAF (Terminal Aerodrome Forecast) report the coming conditions including trends and temporary changes typically for the next twelve to twenty-four hours. The format takes a little getting used.

I’ve compiled a number of reports for a select few cities in the north Atlantic and compressed them into a format the plays nicely with mobile telephones. For the benefit of humans, I’ve prepended the Metar decoded. Let’s check out the balmy Kangerlussuaq (Søndre Strømfjord):

Metar


BGSF 071750Z 04005KT 5000 -SN OVC035 M11/M12 Q1008


BGSF is the airport code (ICAO) followed by the time of the report at UTC. The first two digits represent the day of the month (in this case the seventh) while the next four are the hour (24-hour) and minute (Z refers to Zulu or UTC), thus 17:50.

The next three digits refer to the wind direction (the direction from which the wind comes) over 360 degrees, where 0 is north, 90 is from the east. The next two digits is the wind speed in knots (hence KT). Two knots is roughly one m/s. So 04005KT is roughly 2.5 m/s wind from the northeast. Sometimes you’ll see a G which refers to gusts, so 27020G30KT means 10 m/s gusting to 15 m/s from the west.

The next four digits refer to visibility in meters. 5000 means 5 km visibility. 9999 is typically used for visibility unlimited or at least 10 km.

Then there is the weather type, precipitation, etc. A minus (-) means light while plus is heavy. There are a huge number of codes. Just a few, SH showers, SN snow, FG fog, DZ drizzle, TS thunderstorms, BR mist, RA rain, and many more.

The next zero to many describe the layers of clouds. Scattered, broken, overcast, etc followed by the number of hundreds of feet. Why we mix metric with imperial, I have only guesses. OVC035 means overcast layer of clouds at 3500 feet.

The next numbers refer to the the temperature. The M means minus (below freezing). After the slash is the dew point, the temperature at which precipitation should be expected, or at least 100% relative humidity.

The number with a Q is the barometric pressure in millibar (mbs).