METAR, loosely an acronym for
Meteorological Area
Report are weather reports (not
forecasts).
How to decode a METAR:
For this explanation, I'll be referring to the current metar for my
hometown's airport:
CYXX 070700Z 00000KT 15SM BKN050 OVC100 10/07 A3007 RMK SC6AC2 SLP184
A METAR consists of several parts. The first of which is always the
station identifier
CYXX ICAO code for
Abbotsford,
BC,
Canada
The second is the current date and time, calculated in
GMT (
zulu time)
070700Z Starting with the date, which in this instance is the 7th, and then going on to the time, which is 0700
GMT
And then, on to the actual
weather report, starting with wind direction (in
degrees), then wind
speed (given with the final 2 or 3 letters), possibly with
gusts after it, marked with a G
00000KT Winds are at 000 degrees, 00
Knots (KT) (if there were gusts, it would read something along the lines of 24602G05KT, winds at 246° at 2
knots, gusting to 5
knots)
Next, is
visibility
15SM 15
Statute Miles, other available scales could be NM (
nautical miles) or KM (
kilometers)
And after that is weather elements
no example available on this metar
These are the, ahem, fun bits.
Weather conditions always start with an
intensity/
proximity modifier. + for heavy, nothing for moderate, - for light, and VC for in the vicinity.
After that, possibly, is a
descriptor, which is a 2 letter code for any special parts of this particular weather element.
Weather elements can be divided into 3 different groups. the first is
Precipitation:
The second is obscuration
And the last is "other"
After the
weather elements, is the sky condition. Sky condition is given a condition code, then a layer level (in hundreds of
feet) culmunative (as in, you can't have a "few" layer after a "broken" layer. if that few layer closes off the broken parts of the sky, it becomes an
overcast layer)
If none of the sky is covered at all, the code is simply SKC (for sky clear).
If 1/8 to 2/8 of the sky is covered at the given layer the condtion code is
FEW
If 3/8 to 4/8 of the sky is covered, the condition code is SCT (for
scattered)
If 5/8 to 7/8 of the sky is covered, the condtion code is BKN (for
broken)
If 8/8 of the sky is covered, the condtion code is OVC (for overcast) and no further layers are given
BKN050 OVC100 Broken at 5,000 feet,
Overcast at 10,000 feet
After the sky condtion comes
temperature and
dewpoint, given in degrees
Celsius, in the format
Temperature/
Dewpoint. sub-zero temperatures will be preceded with an 'M'
10/07 A temperature of 10°C with a dewpoint of 7°C
Next is Sea-Level barometric pressure, preceded with an 'A', and calculated with
inches of
mercury
A3007 30.07"
Hg
Finally, is the remarks section, given in plain language or special
acronyms, which starts with the RMK acronym.