How to read a 30 hour TAF

I was looking at some crazy midwest weather today at the Aviation Weather Center and noticed an interesting note in the “Top News”. Apparently, on November 5, 2008 the Terminal Aerodrome Forecast (TAF) will change from a 24 hour forecast period to new format to support a 30 hour TAF.

A quick background information about what a TAF is. A TAF stands for Terminal Aerodrome Forecast. It is a standard weather product that pilots use to look at forecasted weather over the next 24 hours. It will tell pilots what the prevailing weather will be in terms that are important for pilots such as wind, cloud ceiling and visibility. Pilots use this weather product to make determination about what kind of instrument approach they will use at an airport and if they have to file an alternate airport if they can’t make it into their primary airport.

I did a little more research on this new TAF rule and found that this is being done because of some of the factors affecting long haul carriers. Imagine if you an airline pilot and you are trying to plan a 14-18 hour flight. If you have a 24 hour TAF that was issued 4 hours ago, you wouldn’t know the weather at the time you are proposed to land! That’s no good. So now we have 30 hour TAFs to help those long haul guys out.

The FAA took a look and determined that only 32 of the biggest airports in the country will need a 30 hour TAF but to keep all TAFs the same they have determined that all TAFs (even the 24 hour ones) will be in this new format.

I looked at a sample of this new TAF format. It seems the big difference is the addition of the date to the time group. Here is a sample 24 hour TAF in the new format:

KABC 131128Z 1312/1412 14005KT P6SM OVC040
TEMPO 1312/1316 OVC025
FM131600 13015G23KT P6SM OVC015
FM132100 13015G22KT P6SM OVC008
TEMPO 1321/1401 1SM -SN
FM140100 09015KT 3SM BR OVC006
TEMPO 1401/1405 2SM -SN BLSN
FM140500 01015KT 5SM BR OVC006=

As you can tell there is a little extra clutter in there that extra clutter is the date! If you can figure out the first line, the rest of it is easy.

KABC 131128Z 1312/1412 14005KT P6SM OVC040

This forecast which was prepared on the 13th of the month at 11:28 Zulu is is valid from the 13th at 12:00 Zulu to the 14th at 12:00 Zulu. Let’s look at a sample forecast period:

TEMPO 1321/1401 1SM -SN

This forecast line says that temporarily (less than 2 hours) between the 13th at 21:00 Zulu and the 14th at 01:00 Zulu the weather will be 1 statue mile with light snow. See, no problem! Just teach yourself to think of the first 2 digits as dates and all will be well!

If you would like to learn some more about this new forecast the FAA has provided some websites for you to visit. Only one problem. The urls they provided are all in upper case and they only work in lower case! So I converted them all to lower case for you to use without a problem.

A listing of all the affected TAFS:

http://www.weather.gov/os/aviation/pdfs/30_hr_taf_tables.pdf

A FAA explanation of the 30 hour TAF and TAF testbed:

http://www.weather.gov/os/aviation/taf_testbed.shtml

National Guidelines regarding the TAF will be included in an appendix as part of a future update of NWS instruction regarding TAFS:

http://www.nws.noaa.gov/directives/sym/pd01008013curr.pdf

And finally, if you are a forecaster and want to know how to edit the new TAF format (there is a nice graphic there for users as well)

http://aviationweather.gov/notice/taf30.php

Fly Safe (even if you are flying for 18+ hours)