Frequently Asked Aviation Weather Questions (FAQ)

© Peter Lester

Frequently-asked-questions (FAQs) and appropriate answers are found below. They are organized according to chapter of Aviation Weather, 3rd Edition, unless otherwise stated. In cases of overlapping material, some questions and answers may appear in two or more FAQ locations.

The Table of Contents for Aviation Weather is given below to help you sort through the broad topics of each chapter. Click on the Part or Chapter Number and you will go to the page with the appropriate list of questions for that part of the text.

Can’t find relevant FAQ? Email your query to me.

Table of Contents

Part I Aviation Weather Basics
Chapter 1 The Atmosphere
Chapter 2 Atmospheric Energy and Temperature
Chapter 3 Pressure, Altitude, And Density
Chapter 4 Wind
Chapter 5 Vertical Motion and Stability
Chapter 6 Atmospheric Moisture

Part II Atmospheric Circulation Systems
Chapter 7 Scales of Atmospheric Circulations
Chapter 8 Airmasses, Fronts, and Cyclones
Chapter 9 Thunderstorms
Chapter 10 Local Winds

Part III Aviation Weather Hazards
Chapter 11 Wind Shear
Chapter 12 Turbulence
Chapter 13 Icing
Chapter 14 Instrument Meteorological Conditions (IMC)
Chapter 15 Additional Weather Hazards

Part IV Applying Weather Knowledge
Chapter 16 Aviation Weather Resources
Chapter 17 Weather Evaluation for Flight

Appendixes
Appendix A: Conversion Factors
Appendix B: Standard Atmosphere
Appendix C: Dewpoint and Humidity Tables
Appendix D: Standard Meteorological Codes and Graphics for Aviation
Appendix E: Glossary of Weather Terms
Appendix F: Internet Resources and Printed References
Appendix G: Review Question Answers

Part III Aviation Weather Hazards

Q. The section on Thunderstorms is in Part II Chapter 9 while the related hazards are found in Part III. Why are they separated?

A. A problem that arises frequently when discussing aviation weather with pilots is that they often become focused on one hazard, the thunderstorm, and one simple model, the airmass thunderstorm. Furthermore, they have no knowledge of what large scale conditions set up thunderstorms (its always a “cold front!?). Ask them about “windshear” and they will tell you that the thunderstorm is “the” source; ask them about turbulence, IMC, and icing … again, they are most likely to describe the primarily thunderstorm hazard. Not good.

What I have tried to do in Part II of the text is to describe the large and small circulations (cyclones, jet streams, thunderstorms, mountain waves, mountain and valley breezes, etc.) that produce hazards of all types. Then, in part III, I discuss aviation weather hazards in detail. This way, the reader has a better understanding of, for example, exactly what turbulence is and how it can be produced under several DIFFERENT weather conditions … similarly for Windshear, IMC, etc. In my opinion, the reader carries away a much better understanding each phenomena and a broader view of flight weather hazards. The result is a better ability to deal with all hazards, both preflight and inflight.

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Chapter 11 Wind Shear

Chapter 12 Turbulence

Chapter 13 Icing

1. Q. I have heard that there are planned changes in reporting aircraft icing. Is this true? If so, what are the changes and when will they occur?
   
   A. Yes, changes in icing reporting as well as other icing nomenclature are in the works. These changes will result in more useful icing PIREPs and forecasts. Preliminary details have been discussed in the Federal Register and elsewhere. Precise information on the timing for implementation of the changes was not available at the time this FAQ was prepared. Suffice to say, it will happen.
   

Chapter 14 Instrument Meteorological Conditions

1. Q.Is the Weather Depiction Chart really useful? Sometimes, it seems that it is not very accurate.
   
   A. The Weather Depiction Chart is described in Aviation Weather (3rd Ed.) in Chapter 14 on pages 14-9 and 14-10 (figure 14-7). Further description is given in Appendix D (page D-16). It is also explained in Aviation Weather Services (AC 00-45F) in Chapter 5.
   
   This chart is often a few hours old by the time the data are gathered, communicated, analyzed, and finally distributed to you, the user. The problem is that rapidly changing conditions may not be accurately represented by the time you see the chart. For example, IFR conditions due to radiation fog can quickly improve to MVFR or VFR after the sun rises. Similarly a fast moving squall line can result in a change from VFR to IFR in a few minutes. Also, the Weather Depiction Chart may be unrepresentative in rugged terrain due to the separation of stations by mountain ranges.
   
   The best use of the Weather Depiction chart is as a tool for a “first look” at the weather. It gives you a general idea where the ceiling and visibility problems are. The next step is to sharpen that first view of the current weather with more recent and more detailed observational information such as METAR, RADAR, and PIREP data.
   
   
2. Q 2. Is there a plotting model strictly for METAR reports that is similar to the inset in Figure 4-10 and to Appendices on pp. D-15 and D-16? This would help in the interpretation of plotted METAR reports throughout the text.
   
   A. “Yes. In the U.S., the government Aviation Digital Data Service (ADDS) at http://adds.aviationweather.noaa.gov/metars/description2.php provides a METAR plotting model. It is shown below. Note there may be plotting variations for other countries.

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Chapter 15 Additional Weather Hazards