Essential Weather

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This page last updated on 02/28/2014.

Copyright 2001-2014 by Russ Meyer


There are a lot of great aviation weather products offered by the National Weather Service and other government agencies.  In fact, there are so many different depictions of aviation weather that it can get overwhelming.  During flight training, I was taught about all of these weather products.  What I was not taught was how to efficiently use them to form a clear picture of the weather.  They all seemed equally important.  When it came time to plan a flight, I was hard pressed to digest it all.  They ended up seeming like a haphazard jumble of current observations and disconnected forecasts.  I had no clue which were most important and which I could safely ignore.  To look at everything takes an inordinate amount of time, and I usually just don't have that luxury; especially while planning the next leg of a long cross country in a noisy, poorly lit pilot lounge 500 miles from home.  Through experience, I came to realize not all of these weather products were of equal importance; it depends on the type of flying you're doing.

If you are flying a 100 knot airplane on four hour cross-country then there are only four essential weather products.  The rest are "nice-to-haves" but not absolutely essential.  All those other weather products become more important, if you are flying 1000 miles, flying at high altitudes, conducting special flight operations, etc.

VFR Weather Essentials

For a 100 knot airplane on a VFR cross-country, you basically need to know:

  1. METAR - Current weather at the departure airport.
    • Is the weather flyable at the departure airport?
    • What will you have to contend with on take-off?
       
  2. Terminal Area Forecast - Forecast weather at the destination airport.
    • Will the weather be good enough to land when you get to your destination?
    • What will you have to contend with on landing?
    • If your destination airport doesn't issue TAFs, you have other options.  Technically, in a case like this, the FAA expects you to infer weather conditions using the area forecast.  However, it's also possible to look for trends in the last few METAR reports and extrapolate what the conditions will be when you actually arrive.  This method is a bit dicey though, since a rapidly moving front or other dynamic weather condition might cause a sudden change you couldn't anticipate just by looking for trends in METAR history.  Another possibility is to get TAFs from other airports in the vicinity of your destination.  This is probably better than looking at METAR trends and may be a good supplement to an area forecast.
       
  3. Winds Aloft - The forecast winds aloft.
    • What is your expected ground speed?
    • How long will it take to get to your destination?
    • Do you have enough fuel to make it non-stop?
    • What wind correction angle will you have to hold to track your course?
       
  4. Area Forecast - Forecast weather in the general area flight.
    • What will the weather be like enroute?
    • If the weather is marginal along your course, which way do you have to go to find better weather.  Study the area forecast to find an escape route should it become necessary.

IFR Weather Essentials

On an IFR cross-country, you also need to know:

  1. Airmet Zulu - Icing forecast.  Pick up ice in the clouds and that little Cessna will be on the ground in 15 minutes, like it or not!
    • There better not be any ice along your route at your chosen altitude.
    • If your airplane is certified for flight into known icing conditions, you might chance it.
    • You might look at pilot reports to supplement the icing picture.
       
  2. Convective Sigmet - Thunderstorms...don't let the giant roll you between his thumb and forefinger!
    • No convective activity, right?  The embedded stuff is particularly hazardous.
    • With a great RADAR you might be able to pick your way through widely scattered embedded T-storms.

Chocked Full of Weather Goodness

Of course, there are many sources of weather data.  I've used these on occasion:

Caution - FAA at Work!

There are lots of great sources of weather information, including all the links furnished above, but beware...the FAA doesn't recognize them as official sources of weather data.  The FAA only recognizes DUATS and Flight Service Station weather briefings.  (We're talking about weather briefings furnished by a real, live FSS weather briefer...not the pre-recorded weather information the FSS provides.)  It doesn't matter whether or not the information on other government web sites is accurate.

All of this is of little concern unless you have an incident during the flight.  Should that incident involve weather in any way, like a little gust of wind blowing you off the runway on landing, the FAA may  note that you did not receive a weather briefing.  Sure, sure...you got METARs and TAFs from the NWS aviation portal and they were accurate...so what.  You did not get a weather briefing from a source officially recognized by the FAA.  It is possible you could be judged as negligent in the eyes of the FAA, and that might factor into any enforcement action they elect to take.  Something to think about.

A Tale of Two DUATS

Did you know that there are two DUATS?  One is called DUAT and the other DUATS.  The FAA recognizes both as official sources of aviation weather.  They are accessible via the web and are run by different companies contracted by the FAA to provide the service.  They differ somewhat in the way they present information.  Here are a few notable tidbits:

DUAT

  • Content is similar to the official weather products discussed in the FAA publication "Aviation Weather."
  • Contains fairly current, up to date weather information.

DUATS

  • Has easier to understand weather graphics
  • Is notorious for occasionally having out of date weather data.  There have been occasions when some weather maps have been one or two days out of date!  Better check the date stamp on any of the data you retrieve from this site.