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AIM

10/12/17

7−1−46

Meteorology

7−1−24. Wind Shear PIREPs

a. Because unexpected changes in wind speed and

direction can be hazardous to aircraft operations at

low altitudes on approach to and departing from

airports, pilots are urged to promptly volunteer

reports to controllers of wind shear conditions they

encounter. An advance warning of this information

will assist other pilots in avoiding or coping with a

wind shear on approach or departure.

b. When describing conditions, use of the terms

“negative” or “positive” wind shear should be

avoided. PIREPs of negative wind shear on final,”

intended to describe loss of airspeed and lift, have

been interpreted to mean that no wind shear was

encountered. The recommended method for wind

shear reporting is to state the loss or gain of airspeed

and the altitudes at which it was encountered.

EXAMPLE−
1. Denver Tower, Cessna 1234 encountered wind shear,
loss of 20 knots at 400.
2. Tulsa Tower, American 721 encountered wind shear on
final, gained 25 knots between 600 and 400 feet followed
by loss of 40 knots between 400 feet and surface.

1. Pilots who are not able to report wind shear in

these specific terms are encouraged to make reports

in terms of the effect upon their aircraft.

EXAMPLE−

Miami Tower, Gulfstream 403 Charlie encountered an

abrupt wind shear at 800 feet on final, max thrust required.

2. Pilots using Inertial Navigation Systems

(INSs) should report the wind and altitude both above

and below the shear level.

7−1−25. Clear Air Turbulence (CAT) PIREPs
CAT has become a very serious operational factor to

flight operations at all levels and especially to jet

traffic flying in excess of 15,000 feet. The best

available information on this phenomenon must

come from pilots via the PIREP reporting procedures.

All pilots encountering CAT conditions are urgently

requested to report time, location, and intensity (light,

moderate, severe, or extreme) of the element to the

FAA facility with which they are maintaining radio

contact. If time and conditions permit, elements

should be reported according to the standards for

other PIREPs and position reports.

REFERENCE−

AIM, Paragraph 7−1−23 , PIREPs Relating to Turbulence

7−1−26. Microbursts

a. Relatively recent meteorological studies have

confirmed the existence of microburst phenomenon.

Microbursts are small scale intense downdrafts

which, on reaching the surface, spread outward in all

directions from the downdraft center. This causes the

presence of both vertical and horizontal wind shears

that can be extremely hazardous to all types and

categories of aircraft, especially at low altitudes. Due

to their small size, short life span, and the fact that

they can occur over areas without surface precipita-

tion, microbursts are not easily detectable using

conventional weather radar or wind shear alert

systems.

b. Parent clouds producing microburst activity

can be any of the low or middle layer convective

cloud types. Note, however, that microbursts

commonly occur within the heavy rain portion of

thunderstorms, and in much weaker, benign

appearing convective cells that have little or no

precipitation reaching the ground.