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Gust Front Alert
(c) MULTIPLE WIND SHEAR ALERTS
This is what the controller sees on his/her ribbon display
in the tower cab.
27A WSA 20K+ RWY 250 20
27D WSA 20K+ RWY 250 20
(See FIG 7-1-17 to see how the TDWR/WSP determines
the gust front/wind shear location.)
This is what the controller will say when issuing the
MULTIPLE WIND SHEAR ALERTS. RUNWAY 27
ARRIVAL, WIND SHEAR ALERT, 20 KT GAIN ON
RUNWAY; RUNWAY 27 DEPARTURE, WIND SHEAR
ALERT, 20 KT GAIN ON RUNWAY, WIND 250 AT 20.
In this example, the controller is advising arriving and
departing aircraft that they could encounter a wind shear
condition right on the runway due to a gust front
(significant change of wind direction) with the possibility
of a 20 knot gain in airspeed associated with the gust front.
Additionally, the airport surface winds (for the runway in
use) are reported as 250 degrees at 20 knots.
FAA Order 7110.65, Air Traffic Control, Low Level Wind
Shear/Microburst Advisories, Paragraph 3-1-8b2(d).