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Pilot's Handbook of Aeronautical Knowledge
Aviation Weather Services

Aviation Weather Reports

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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

3. Date and time of report—depicted in a six-digit group
(161753Z). The first two digits are the date. The last
four digits are the time of the METAR, which is always
given in coordinated universal time (UTC). A "Z" is
appended to the end of the time to denote the time is
given in Zulu time (UTC) as opposed to local time.

4. Modifier—denotes that the METAR came from an
automated source or that the report was corrected.
If the notation "AUTO" is listed in the METAR, the
report came from an automated source. It also lists
"AO1" or "AO2" in the remarks section to indicate
the type of precipitation sensors employed at the
automated station.

When the modifier "COR" is used, it identifies a
corrected report sent out to replace an earlier report
that contained an error (for example: METAR KGGG
161753Z COR).

5. Wind—reported with five digits (14021) unless the
speed is greater than 99 knots, in which case the
wind is reported with six digits. The first three digits
indicate the direction the true wind is blowing in
tens of degrees. If the wind is variable, it is reported
as "VRB." The last two digits indicate the speed of
the wind in knots unless the wind is greater than 99
knots, in which case it is indicated by three digits.
If the winds are gusting, the letter "G" follows the
wind speed (G26). After the letter "G," the peak gust
recorded is provided. If the wind varies more than 60°
and the wind speed is greater than six knots, a separate
group of numbers, separated by a "V," will indicate the
extremes of the wind directions. Figure 12-7 shows
how the TDWR/Weather System Processor (WSP)
determines the true wind, as well as gust front/wind
shear location.

Example of what the controller sees on the ribbon display in the tower cab.
Figure 12-7. Example of what the controller sees on the ribbon
display in the tower cab.

6. Visibility—the prevailing visibility (¾ SM) is reported
in statute miles as denoted by the letters "SM." It is
reported in both miles and fractions of miles. At times,
runway visual range (RVR) is reported following the
prevailing visibility. RVR is the distance a pilot can
see down the runway in a moving aircraft. When RVR
is reported, it is shown with an R, then the runway
number followed by a slant, then the visual range
in feet. For example, when the RVR is reported as
R17L/1400FT, it translates to a visual range of 1,400
feet on runway 17 left.

7. Weather—can be broken down into two different
categories: qualifiers and weather phenomenon
(+TSRA BR). First, the qualifiers of intensity,
proximity, and the descriptor of the weather will
be given. The intensity may be light (-), moderate
( ), or heavy (+). Proximity only depicts weather
phenomena that are in the airport vicinity. The notation
"VC" indicates a specific weather phenomenon is
in the vicinity of five to ten miles from the airport.
Descriptors are used to describe certain types of
precipitation and obscurations. Weather phenomena
may be reported as being precipitation, obscurations,
and other phenomena such as squalls or funnel clouds.
Descriptions of weather phenomena as they begin or
end, and hailstone size are also listed in the remarks
sections of the report. [Figure 12-8]

8. Sky condition—always reported in the sequence
of amount, height, and type or indefinite ceiling/
height (vertical visibility) (BKN008 OVC012CB).
The heights of the cloud bases are reported with a
three-digit number in hundreds of feet AGL. Clouds
above 12,000 feet are not detected or reported by an
automated station. The types of clouds, specifically
towering cumulus (TCU) or cumulonimbus (CB)
clouds, are reported with their height. Contractions
are used to describe the amount of cloud coverage and
obscuring phenomena. The amount of sky coverage is
reported in eighths of the sky from horizon to horizon.
[Figure 12-9]

9. Temperature and dew point—the air temperature and
dew point are always given in degrees Celsius (C) or
(°C 18/17). Temperatures below 0 °C are preceded by
the letter "M" to indicate minus.
10. Altimeter setting—reported as inches of mercury
("Hg) in a four-digit number group (A2970). It is
always preceded by the letter "A." Rising or falling
pressure may also be denoted in the remarks sections
as "PRESRR" or "PRESFR" respectively.

11. Zulu time—a term used in aviation for UTC which
places the entire world on one time standard.

 

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