September 1, 1993
Don't look now, but the National Weather Service and the Federal Aviation Administration are changing the code words used in terminal forecasts (FTs) and surface observations (SAs). As a matter of fact, they're even changing the names of these reports, all in the name of global conformity to International Civil Aviation Organization (ICAO) standards. So get ready to forget about FTs and SAs.
In the future, these reports will be called TAFs (terminal area forecasts) and METARs (meteorological reports — aviation routine), respectively. As for the contents of these reports, well, they'll be changed, too. So for all of you who struggled through ground school to learn what C20 BKN 3RW- 2220 CHC C8 OVC 1TRW 3015G25 AFT 20Z meant in an FT (translation: "ceiling 2,000 broken, visibility 3 miles in light rainshowers, wind 220 degrees at 20 knots, with a chance of ceiling 800 feet overcast and visibility 1 mile in a thunderstorm and rainshower with wind from 300 degrees at 15 gusting to 25 knots after 2000 Zulu") or what M10 OVC 3/4TRW 103/65/61/2215G25/992 R22LVR27 (translation: "Measured 1,000 feet overcast, visibility 3/4-mile in thunderstorm and rainshowers, atmospheric pressure 1010.3 millibars, temperature 65 degrees Fahrenheit, dew point 61 degrees Fahrenheit, wind 220 degrees at 15 gusting to 25 knots, altimeter 29.92, Runway 22L visual range 2,700 feet") meant in an SA, get ready to relearn.
Under the ICAO code, the FT — er, TAF — mentioned above would read 22020KT 3SM -SHRA BKN 020 FM 20 30015G25KT 3SM SHRA OVC015 PROB40 2022 1/2SM TSRA OVC008CB. (Wind 220 at 20 miles, visibility 3 miles in light rainshowers, broken sky at 2,000 feet, from 2000 Zulu wind 300 degrees at 15 gusting to 25 knots, visibility 3 statute miles in rainshowers, 40- percent probability of wind 200 degrees at 22 knots and visibility 1/2 statute mile in thunderstorm and rainshowers, with an overcast ceiling at 800 feet and cumulonimbus clouds.)
The SA — er, METAR — in the previous paragraph would read 22015G25KT 3/4SM R22L/2700FT TSRA OVC 010CB 18/16 A2992. (Wind 220 degrees at 15 gusting to 25 knots, visibility 3/4-statute mile, Runway 22L visual range 2,700 feet, thunderstorm and rainshower, overcast ceiling at 1,000 feet in cumulonimbus clouds, temperature 18 Celsius, dew point 16 Celsius, altimeter 29.92.)
I can sense that some of you are getting panicky. But don't worry; these changes won't occur all at once. They'll be introduced in two phases. And there will doubtless be plenty of educational and informational material distributed as part of the switchover.
The first to be affected will be those pilots flying into the United States from foreign locations and landing at some 250 landing rights airports. For these pilots, the changes take effect immediately. The angst would be most extreme for pilots relying solely on straight, government-issue textual reports. Fortunately, most of us contact a flight service station — or its foreign equivalent — for our weather briefings, and its personnel can be helpful in deciphering any code problems.
Also, we can expect that any DUAT or private suppliers of weather information will continue to include plain-language translations of coded text.
The next phase takes effect on January 1, 1996. That's when the FTs and SAs become history within the United States, and all of us will have to use TAFs, METARs, and their attendant strange new codes. So far, there's been no word on whether area forecasts, winds aloft, and other textual reports are due to be changed.
Until that happy New Year's Day, we'll continue to see and use FTs and SAs for weather briefing and flight planning. We're using what the meteorological community calls the "North American code," and frankly, we've been pretty lucky to retain our weather codes and abbreviations for as long as we have. The rest of the world has been using METARs and TAFs for years.
We should also be glad that certain concessions were granted us. Even though we'll have to relearn some abbreviations, at least we won't be reading ceilings and visibilities in meters, seeing barometric pressure in hectopascals or millibars, or dealing with sky cover in terms of octas (division of the sky into eighths). That's how other nations report their aviation weather.
With a little practice, learning the new codes shouldn't really be too much of a problem. Sky cover will still be given in terms of clear, scattered, broken, or overcast, for example. Also, many of the abbreviations, while new, are easily deciphered. RA means rain, TS stands for thunderstorm, FG is fog, and FZ stands for freezing. Where barometric pressure is reported, the prefix "A" is attached to remind you that the setting is in inches of mercury. (A "Q" prefix indicates that the setting is being given in millibars or hectopascals, which for practical purposes are one and the same.)
Other changes aren't so kind. Cloud bases are given in a three- digit format; a 1,000-foot ceiling, for example, is published as 010. And some of the abbreviations obviously come from non-English-language roots. The abbreviation for shallow (as in shallow ground fog) is MI, patches are BC, hail is GR, and smoke is FU.
We also lost the great battle to preserve the reporting of surface temperatures in Fahrenheit. From 1996 on, it'll be an all-Celsius world for pilots.
You'll see the terms PROB, TEMPO, and BECMG in the METARs. If you see PROB40 2022 1/2SM RASH, this means there's a 40-percent probability of half-mile visibility in rainshowers between 2000 and 2200 Z. It's a bit like the "chance of" (CHC) reports we've seen in FTs.
TEMPO equates to the FTs' "occasional" (OCNL) notation. Strictly speaking, TEMPO means to expect temporary changes lasting less than one hour and, in total, less than half of the published two-digit beginning and ending time period. TEMPO 0407 1DZ, therefore, means temporary 1-mile visibility in drizzle between 0400 and 0700 Z.
BECMG simply means that a change is expected — again, within a time frame defined by two, two-digit abbreviations of Zulu time.
The most helpful hint is to remember that both METARs and TAFs list surface winds first, then visibility (in statute miles), followed by weather conditions and sky cover. In the case of METARs, temperature, dew point, and barometric pressure follow in the accustomed sequence.
There's plenty of time to learn all the details of the new reports and abbreviations, and we'll be sure to keep reminding you as 1996 draws nearer. Those wanting to bone up now can contact the American Meteorological Society (45 Beacon Street, Boston, Massachusetts 02108; telephone 617/227-2425) to obtain a copy of the World Meteorological Organization's publication number 782, Aerodrome Reports and Forecasts: A User's Guide. You must prepay, and the price is $21.
Understandably, the AMS's supply of number 782 is exhausted. I've been told a new batch is on the way, and you'll get your copy — eventually — after you give your money to the AMS.
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