It isn't just pilots who are concerned about the changeover to METAR and TAF weather reporting. Air traffic controllers are scrambling to learn how to break the new code, too. New York TRACON's resident expert on METAR shows how the new weather reports aren't really as tough to figure out as they look ... and are actually better than the old familiar SA reports in a number of important respects.
May 22, 1996
The results of the New York TRACON's Safety Survey "Are You
Ready for METAR?" are in, and the results are unanimous:
No one around here knows anything about METAR!
Well, in the interest of safety, the mystery of METAR can now
METAR is the ICAO (International Civil Aviation Organization)
meteorological format for Aviation Routine Weather Reports. In
order to enhance safety, the U.S. agreed to modifying its domestic
weather codes to match ICAO's standards.
This isn't exactly late-breaking news. The first changes began
happening in 1993! Although these changes were mostly transparent
to domestic operations, the FAA made it known to aviation user
groups early-on that the changes would be coming and several prominent
aviation magazines have run articles describing in general the
format changes. And yet, no one thought to tell the controllers.
Not until the change was almost here, that is.
The good news is that METAR was NOT implemented on the originally-planned
date of January 1, 1996. The FAA and NWS just weren't ready in
time, lucky for us. The new implementation date is July 1, 1996,
Here is the sequence of elements in a METAR report:
Type of report
Time of report
Weather and obstructions to visibility
Temperature and dew point (in CELSIUS!)
Here is a quick overview of each of the elements and what's new
and different about them:
- 1. Type of report:
There are two types of report: (a) the
METAR, which is a routine observation report, and (b) the SPECI,
which is a Special METAR weather observation.
- 2. Station designator:
The METAR codes uses ICAO 4-letter
station identifiers. In the contiguous 48 states, the 3-letter
domestic station identifier is prefixed with a "K",
i.e. the domestic identifier for Newark is EWR while the ICAO
identifier is KEWR.
- 3. Time of report:
The time is the time the observation
was taken in UTC, as it is now, but will also be preceded by the day of the
month and followed by the letter "Z", e.g. 091250Z.
- 4. Wind:
In METAR reports, the wind will be the first weather
element. Also, the wind will be reported with three digits for
the direction and two digits for the speed (3 digits if needed).
If the wind is gusty, it is reported after the speed with a "G",
followed by the highest gust reported (in 2 or 3 digits). It will
be appended with the abbreviation "KT" to denote the
use of knots for wind speed.
Winds now reported as 1308 will be shown as 13008KT.
Winds now reported as 0832G45 will be shown as
Also, if the winds are variable,
the information will immediately follow the wind group instead
of being in the Remarks.
If you think about it, this actually is an improvement to the
way winds are now done.
- 5. Visibility:
Visibility is reported in statute miles
with "SM" appended to it. If Runway Visual Range is
reported, it will immediately follow, in the format: R(Runway)/(Visual
Range)FT. The 'R' identifies the RVR group.
Again, this is all pretty much straight forward and shouldn't
be too hard to get used to.
- 6. Weather:
Now this is where things start to get confusing.
All of the weather abbreviations will be in two letter codes,
and some of the codes don't exactly lend themselves to immediate
understanding. The big ones are pretty easy, such as Thunderstorm
= TS and Rain = RA, but some are just weird, like Hail = GR and
Smoke = FU. The NWS folks say these are derived from the French words,
but personally, I think there are some 'inside jokes' behind those two.
Also, weather will be broken down into sub-categories and will
be reported in the following format:
This will apply ONLY to the first type of precipitation
reported. A minus sign (-) denotes light, no sign denotes medium,
and a plus sign (+) denotes heavy.
Applies to and reported ONLY for weather occurring
in the vicinity of the airport (5-10 NM). It is denoted by the
The standard METAR format has these seven
descriptors that apply to the precipitation or obstruction to
There are six types of precipitation in
the METAR code:
- Obstructions to Visibility:
There are eight types of obstructing
phenomena in the METAR code:
Fog (FG) is forecast only when the visibility is less
than 5/8 mile; otherwise mist (BR) is forecast.
There are five categories of Other Weather Phenomena
which are reported when they occur:
- 7. Sky Condition:
The sky condition as reported in METAR
represents a significant change from the way sky condition is
presently reported. In METAR, the sky condition is reported in
the following format:
The amount of sky cover is reported in eights of sky cover,
using the contractions:
Now, what is interesting is that there is no ceiling layer designated
in the METAR code. For aviation purposes, the ceiling is the lowest
reported broken or overcast layer, or vertical visibility into
an obscuration. Also, there is no provision for reporting thin
One more oddball detail: automated weather reporting stations report CLR
(meaning sky clear below 12,000 feet) instead of SKC. Go figure!
Cloud bases are reported with three digits in hundreds
Sky conditions are 1100' scattered, ceiling 1500' overcast.
If towering cumulus (TCU) or cumulonimbus (CB) are present,
they are reported after the height which represents their base.
This is a nice feature of the METAR format. It really helps you
develop a good visual picture of what the weather is doing.
- Vertical Visibility:
Total obscurations are reported in the format
"VVhhh", where VV denotes Vertical Visibility and the
hhh is the vertical visibility in hundreds of feet. There is no
provision in METAR to report partial obscurations:
1SM FG VV003
Prevailing visibility is 1 statute mile in fog, with a vertical
visibility of 300 ft.
- 8. Temperature and Dew Point:
Here's the part that will
probably cause the most grief. The temperature and dew point will
be reported in a two digit form in Celsius. Also, temperatures
below zero will be prefixed with an "M".
- 9. Altimeter:
Minor changes here. The altimeter will be
reported in a full four digit format prefixed with an "A".
- 10. Remarks:
This is where the U.S. domestic METAR will
deviate significantly from the rest of the world. Normally, remarks
in METAR are limited to reporting operational significant weather
(i.e. lightning: LTGICCCCA), the beginning and ending times of
certain weather phenomena, and low-level wind shear reports. Until
we get the full training packages, we can't be exactly sure what's
going to be in the Remarks. In any case, the contraction "RMK"
will precede the remarks themselves. "RE" stands for
"Recent Event" (not "Rain Ended"). "WS
is for "Wind Shear", followed by "TKO" (take-off)
or "LDG" (landing), and "RWxx" which will
denote the runway affected.
RMK REFZDZB45 WS TKO RW04L
Remarks: Recent Event: Freezing Drizzle, Began 45 minutes past
the hour; Wind Shear: On Take-off, Rwy 041.
This should give you a pretty good overview of what to expect.
Also, don't sweat trying to memorize all the new weather codes.
There's a nifty METAR/TAF quick refererence card
that you can print out and use as a crib sheet.
Once everyone gets comfortable with the new format, I think most
will find it simple to understand and may actually be able to
better visualize what the weather is doing. There are some weather
abbreviations that we'll never see around here, and the commonly
used ones will become second nature soon enough. And if you do
see one of the strange ones, chances are you'll have plenty of
pilots to tell you what it is, because that's what they're trying
to avoid. Think about it: if you've got "VA" in the
weather sequence at your primary airport, you've got bigger problems
to worry about than learning a new weather code.
No one need to get too uptight about METAR. It's just winds, temp.
and weather, after all. All the same things are there, it's just
the way they're being presented that's new. Happy vectors, and