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Pilot's Handbook of Aeronautical Knowledge
Aviation Weather Services

Aviation Forecasts

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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

Area forecast region map.
Figure 12-12. Area forecast region map.

Each AIRMET bulletin has a fixed alphanumeric designator,
numbered sequentially for easy identification, beginning with
the first issuance of the day. Sierra is the AIRMET code used
to denote IFR and mountain obscuration; Tango is used to
denote turbulence, strong surface winds, and low-level wind
shear; and Zulu is used to denote icing and freezing levels.

Example:
DFWTWA 241650
AIRMET TANGO UPDT 3 FOR TURBC… STG
SFC WINDS AND LLWS VALID UNTIL 242000
AIRMET TURBC… OK TX…UPDT
FROM OKC TO DFW TO SAT TO MAF TO CDS
TO OKC OCNL MDT TURBC BLO 60 DUE TO
STG AND GUSTY LOW LVL WINDS. CONDS
CONTG BYD 2000Z

Explanation:
This AIRMET was issued by Dallas–Fort Worth on the
24th day of the month, at 1650Z time. On this third update,
the AIRMET Tango is issued for turbulence, strong surface
winds, and low-level wind shear until 2000Z on the same
day. The turbulence section of the AIRMET is an update
for Oklahoma and Texas. It defines an area from Oklahoma
City to Dallas, Texas, to San Antonio, to Midland, Texas,
to Childress, Texas, to Oklahoma City that will experience
occasional moderate turbulence below 6,000 feet due to
strong and gusty low-level winds. It also notes that these
conditions are forecast to continue beyond 2000Z.

SIGMET
SIGMETs (WSs) are inflight advisories concerning nonconvective
weather that is potentially hazardous to all
aircraft. They report weather forecasts that include severe
icing not associated with thunderstorms, severe or extreme
turbulence or clear air turbulence (CAT) not associated with
thunderstorms, dust storms or sandstorms that lower surface
or inflight visibilities to below three miles, and volcanic
ash. SIGMETs are unscheduled forecasts that are valid for
4 hours, but if the SIGMET relates to hurricanes, it is valid
for 6 hours.

A SIGMET is issued under an alphabetic identifier, from
November through Yankee, excluding Sierra and Tango.
The first issuance of a SIGMET is designated as an Urgent
Weather SIGMET (UWS). Reissued SIGMETs for the same
weather phenomenon are sequentially numbered until the
weather phenomenon ends.