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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

Surface analysis chart.
Figure 12-14. Surface analysis chart.

Explanation of Figure 12-13:
The heading indicates that this FD was transmitted on the 15th
of the month at 1640Z and is based on the 1200Z radiosonde.
The valid time is 1800Z on the same day and should be
used for the period between 1700Z and 2100Z. The heading
also indicates that the temperatures above 24,000 feet MSL
are negative. Since the temperatures above 24,000 feet are
negative, the minus sign is omitted.

A four-digit data group shows the wind direction in reference
to true north and the wind speed in knots. The elevation at
Amarillo, Texas (AMA) is 3,605 feet, so the lowest reportable
altitude is 6,000 feet for the forecast winds. In this case,
"2714" means the wind is forecast to be from 270° at a speed
of 14 knots.

A six-digit group includes the forecast temperature aloft.
The elevation at Denver (DEN) is 5,431 feet, so the lowest
reportable altitude is 9,000 feet for the winds and temperature
forecast. In this case, "2321-04" indicates the wind is forecast
to be from 230° at a speed of 21 knots with a temperature
of –4 °C.

Weather Charts

Weather charts are graphic charts that depict current or
forecast weather. They provide an overall picture of the
United States and should be used in the beginning stages of
flight planning. Typically, weather charts show the movement
of major weather systems and fronts. Surface analysis,
weather depiction, and radar summary charts are sources of
current weather information. Significant weather prognostic
charts provide an overall forecast weather picture.

Surface Analysis Chart
The surface analysis chart depicts an analysis of the current
surface weather. [Figure 12-14] This chart is a computer
prepared report that is transmitted every 3 hours and covers
the contiguous 48 states and adjacent areas. A surface analysis
chart shows the areas of high and low pressure, fronts,
temperatures, dew points, wind directions and speeds, local
weather, and visual obstructions.

Surface weather observations for reporting points across
the United States are also depicted on this chart. Each of
these reporting points is illustrated by a station model.

[Figure 12-15] A station model includes:
• Type of observation—a round model indicates an
official weather observer made the observation. A
square model indicates the observation is from an
automated station. Stations located offshore give data
from ships, buoys, or offshore platforms.
• Sky cover—the station model depicts total sky cover
and is shown as clear, scattered, broken, overcast, or
obscured/partially obscured.
• Clouds—represented by specific symbols. Low cloud
symbols are placed beneath the station model, while
middle and high cloud symbols are placed directly
above the station model. Typically, only one type of
cloud will be depicted with the station model.