c. Include in the SIGMET the SIGMET number and the term "convective" when applicable.
(Convective SIGMETs are issued for tornadoes, lines of thunderstorms, embedded thunderstorms, and
hail 3/4 inch or greater.) Include also in the SIGMET a general description of the area affected and a
brief description of the type of weather.
NOTE: While the message should be brief, it must contain enough information to alert aviators to
significant weather conditions along their route of flight and to enable them to decide whether or not
they should contact a flight service station (FSS) for more detailed information.
EXAMPLE: "Attention all aircraft, convective SIGMET Delta Three. From Fort Rucker to Crestview
to Pensacola. Embedded thunderstorms and severe clear icing below one-five thousand feet. Expected
to continue beyond one-niner-zero-zero UTC."
16.
ISSUE LOW-LEVEL WIND SHEAR ALERT SYSTEM (LLWAS) ADVISORIES
At those locations equipped with an LLWAS, the local controller shall provide wind information
as shown below. The LLWAS detects possible low-level wind shear conditions around the periphery of
an airport. It does NOT detect wind shear beyond that limitation.
a. When low-level windshear is reported by pilots or detected on any of the Doppler or
LLWAS, a statement shall be included on the ATIS for 20 minutes following the last report or indication
of windshear. At facilities without ATIS, ensure that windshear information is broadcast to all arriving
and departing aircraft for 20 minutes following the last report or indication of windshear.
b. If an alert is received, issue the center field wind and the displayed field boundary wind.
EXAMPLE: "Wind shear alert. Center field wind two-seven-zero at one-zero. East boundary wind
one-eight-zero at two-five."
c. If unstable conditions produce multiple alerts, issue an advisory that there are wind shear
alerts in two, several, or all quadrants. Then issue the center field wind from the LLWAS display
followed by the field boundary wind most appropriate to the aircraft operation.
EXAMPLE: "Wind shear alert all-quadrants. Center field wind two-one-zero at four, west boundary
wind one-four-zero at two-two."
3-7
AV2400
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