Aviation Weather: Meteorological Aviation Routine Report (METAR)

I promised you last Friday that I would write about one of the aviation weather products this week. There is one type of surface weather report that some of you may have seen on some weather sites on the internet, the METAR. METAR stands for Meteorological Aviation Routine Report. METARs, used worldwide, are coded reports with each country making modifications for use in their specific country.

Routine METARs are done on an hourly basis, usually at airports. Some METARs are done automatically (without the benefit of humans) and will include the code "AUTO". Other METARs are done for special weather reports and are labeled "SPECI". METAR's are but one of the sources of aviation weather information used by pilots as a part of their pre-flight planning and while enroute. I access METARs over the internet, which I'll get to in a moment, and most of the METARs that I have accessed are those done on an hourly basis.

Ok, I mentioned that METAR reports are coded, and I'll include an example in a moment along with a translation. You may have seen a METAR, perhaps on Intellicast Weather or Weather Underground, hopefully these links will take you directly to pages for Newark Liberty International Airport in Newark, NJ where you can see the coded METAR. On Weather Underground, look for the METAR under current data on the left side of the page, they provide a nice METAR faq where you can go to learn about how to decode the METAR. The METAR on the intellicast website should be in the box labeled current conditions near the top left side of the page.

Here is a coded METAR and translation which I got using the form found on the  the NWS Aviation digital data website (note 1):

METAR (code) text: KEWR 291951Z 06008KT 2SM RA BR BKN010 OVC020 06/03 A3001 RMK AO2 SLP161 CIG 009V011 P0010 T00560033

TRANSLATION (note 2,3):
Conditions at: KEWR (NEWARK , NJ, US) observed 1951 UTC 29 February 2012
Temperature: 5.6°C (42°F)
Dewpoint: 3.3°C (38°F) [RH = 85%]
Pressure (altimeter): 30.01 inches Hg (1016.3 mb)
[Sea-level pressure: 1016.1 mb]
Winds: from the ENE (60 degrees) at 9 MPH (8 knots; 4.2 m/s)
Visibility: 2.00 miles (3.22 km)
Ceiling: 1000 feet AGL
Clouds: broken clouds at 1000 feet AGL
overcast cloud deck at 2000 feet AGL
Weather: RA BR  (rain, mist)

The coding in METARs take some getting used, and are covered in the FAA Private Pilot Exam. I like METARs and will look for METARs before I go on a scenic flight. Checking out the METARs are also an easy way to see weather conditions around my region.

Notes:
(1) This page is used to access both METARs and TAFs (Terminal Aerodrome Forecasts), a forecast for a five mile radius around the airport mentioned in the TAF. I'll cover those in a later article. Most of your major international airports in the US will have TAF reports for their terminal (5 mile radius) area.

(2) UTC stands for coordinated time universal or universal time. You may see UTC time referred to by the letter "Z" in coded reports such as the METAR above. UTC is also Greenwich Mean Time (obtained at the observatory in Greenwich England (near London). UTC time is used for all aviation weather information products, and takes a little getting used. If you want to know what UTC time is in your time zone, go to this website.

(3) The National Weather Service has a guide that may be found here that aids in translating the coding used in METARs and TAFs.

References:

U.S. Department of Transportation, Federal Aviation Administration, Flight Standards Service. Pilots Handbook of Aeronautical Knowledge (2008), pp 12-6 to 12-8 obtained from this page on the FAA website where individual chapters may be downloaded. Chapter 12 is devoted to Aviation Weather Services.

U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service. U.S. Department of Transportation, Federal Aviation Administration. Aviation Weather Services, Advisory Circular AC 00-45G (2011) obtained from the FAA, pp. 3-1 to 3-31.