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Pilot's Handbook of Aeronautical Knowledge
Aviation Weather Services

Weather Charts

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Pilot's Handbook of Aeronautical Knowledge

Preface

Acknowledgements

Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making

Appendix

Glossary

Index

Sample station model and weather chart symbols.
Figure 12-15. Sample station model and weather chart symbols.

• Sea level pressure—given in three digits to the nearest
tenth of a millibar (mb). For 1,000 mbs or greater,
prefix a 10 to the three digits. For less than 1,000 mbs,
prefix a 9 to the three digits.
• Pressure change/tendency—pressure change in tenths
of mb over the past 3 hours. This is depicted directly
below the sea level pressure.
• Precipitation—a record of the precipitation that has
fallen over the last 6 hours to the nearest hundredth
of an inch.
• Dew point—given in degrees Fahrenheit.
• Present weather—over 100 different weather symbols
are used to describe the current weather.
• Temperature—given in degrees Fahrenheit.
• Wind—true direction of wind is given by the wind
pointer line, indicating the direction from which the
wind is coming. A short barb is equal to 5 knots of
wind, a long barb is equal to 10 knots of wind, and a
pennant is equal to 50 knots.

Weather Depiction Chart
A weather depiction chart details surface conditions as
derived from METAR and other surface observations. The
weather depiction chart is prepared and transmitted by
computer every 3 hours beginning at 0100Z time, and is valid
at the time of the plotted data. It is designed to be used for
flight planning by giving an overall picture of the weather
across the United States. [Figure 12-16]

This type of chart typically displays major fronts or areas
of high and low pressure. The weather depiction chart
also provides a graphic display of IFR, VFR, and MVFR
(marginal VFR) weather. Areas of IFR conditions (ceilings
less than 1,000 feet and visibility less than three miles) are
shown by a hatched area outlined by a smooth line. MVFR
regions (ceilings 1,000 to 3,000 feet, visibility 3 to 5 miles)
are shown by a nonhatched area outlined by a smooth line.
Areas of VFR (no ceiling or ceiling greater than 3,000 feet
and visibility greater than five miles) are not outlined.

 

12-16