Funny story for you with humor that only a pilot may understand. I was checking the ASOS at my home airport on the way in tonight and I heard something interesting on the radio:

Automated weather, time 2156 zulu, winds 290 at 9, visibility 10, sky clear, light rain, temperature 22, dewpoint 16, altimeter 30.22

Sky Clear and Rain? I’m confused. I’m not sure where the rain came from? I sure didn’t see any. Now here is the really funny coincidence, as I was listening to the radio on the way home, Creedence Clearwater Revival came on singing, “Have you ever seen the rain?” Now if you aren’t familiar with the lyrics, let me quote the chorus for you:

I want to know, have you ever seen the rain?
I want to know, have you ever seen the rain?
Comin down on a sunny day?

No, CCR, I haven’t seen the rain come down on a sunny day, but it sure wasn’t for the lack of trying.

Now, to turn this into an educational experience, I’m going to add a quick lesson. How do you seriously know when an ASOS might be reporting inaccurate or corrupted data? You can look for a “$” sign at the end of the METAR report. Here’s an example:

260256Z AUTO 19007KT 8SM FEW080 22/19 A3002 RMK AO2 56010 T02220194 LTG DSNT NW-NE SLP158 $

You know from the $ sign at the end of the report that maintenance is needed on the weather station system making this report. That is the station’s way of saying, “I’m in need of some attention.” You don’t know what is broke but you know that something may be inaccurate. I would recommend trying to find another surface observation in the area and compare it to the other to make sure they are reporting somewhat similar weather.

Fly Safe.

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)

As reported in this month’s Flying Magazine, the National Weather Association (NWA) is offering a free online weather theory course.   It is designed to help general aviation pilots understand how weather theory affects flying.
When you go to their website (see links below) you will find they currently offer two “modules”  An introduction module and an aircraft performance module.  To begin you download each module to your computer.  You are actually downloading a zip file which contains an executable file that will launch a  Macromedia Shockwave presentation.  Each download is roughly 22 megabytes.  The introduction module goes over:

• Moisture
• Vertical Motion
• Stability

The aircraft performance module goes over…well, how weather affect aircraft performance.

I found both tutorials and courses to be extremely informative and highly educational.   The aircraft performance is very through and goes through many different aircraft performance scenarios and how weather would affect that situation.    I also learned from their website that they are planning on releasing two more courses Aviation Weather Forecasts and Application of Weather Theory.  I look forward to both additional courses.

My only complaints about this course would be that it is advertised as online and really you download the course which makes a “offline” course and also the menu and navigation were a little bit clumsy.  Once you start a section, you can’t stop it.   I actually had to use CTL-ALT-DEL and the task manager to end it when I had to stop it mid course.

You can check it out and review it for yourself at http://www.nwas.org/committees/aviation/WeatherTheory/

Enjoy.  I look forward to hearing your comments about the course.