I was surprised when I read recently that many new airline pilot job applicants struggle with decoding basic metar weather reports. It would seem to me that if you’ve done enough flying to reach the interview stage with a commercial carrier, you would have interpreted hundreds if not thousands of metars along the way.
Maybe it’s the invention of software that can translate metars into “plain English” that has caused such befuddlement among would-be airline pilots. Still, with a little practice metars aren’t hard to grasp – and being able to do so could save your bacon if you’re staring down an un-translated report and need to make a go/no-go decision in marginal weather.
First things first: A metar is a weather report issued near the end of each hour, while a SPECI is a special metar that alerts pilots of new hazards, such as thunderstorms or low ceilings and visibility that arise during the hour.
Metar information is always given in a specific order, and that’s key to understanding how to read one, especially when they get complicated. (It’s also important to realize that if data is missing, such as the altimeter setting, for example, it will simply be omitted.)
The order in which metar data is given is: Where; When; Wind; Visibility; Significant Hazards; Clouds; Temp/Dew Point; Altimeter Setting; and Remarks.
Let’s break down each of these in the following Metar:
METAR KABC 121755Z AUTO 21016G24KT 180V240 1SM R11/P6000FT -RA BR BKN015 OVC025 06/04 A2990 RMK A02 PK WND 20032/25
KABC is the airport identifier. All controlled airports in the continental U.S. begin with the letter K.
All dates and times are UTC using the 24-hour clock. The first two digits are the day (sorry, you have to know the month) and the last four are the time, followed by a Z to indicate UTC (“Zulu” time). In this example, it’s the 12th day of the month and the time of the observation was 17:55 UTC.
(NOTE: The word AUTO simply tells us this is an automatic observation with no human intervention. If it said COR instead, that would mean it is a corrected observation. If a human performed the observation, it wouldn’t say anything.)
The wind is given in tens of degrees from true north with the next two digits telling us is the speed in knots. G means gusts to whatever max speed, and V means variable by 60 degrees or more for winds that are greater than 6 knots (the term VRB will be used for variable winds 6 knots or less). So in this example, the wind is blowing from 210 degrees at 16 knots with peak gusts to 24 knots. The winds are also variable from 180 degrees to 240 degrees.
Visibility is given in statute miles and fractions, with spaces between numbers denoting fractions. In our example the vis is 1 statute mile. If the visibility is 1 mile or less or the runway visual range is 6,000 feet or less, the RVR will also be given. In this example, the RVR for Runway 11 is reported as 6,000 feet (an M or P will be affixed to tell us whether the value is lower or higher than reportable RVR; a V will be used if the RVR is variable, e.g. 2000V4000).