5/19/22
AIM
FIG 7
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1
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16
Warning Boxes
(b)
LLWAS was fielded in 1988 at 110 air-
ports across the nation. Many of these systems have
been replaced by new TDWR and WSP technology.
While all legacy LLWAS systems will eventually be
phased out, 39 airports will be upgraded to
LLWAS
−
NE (Network Expansion) system. The new
LLWAS
−
NE systems not only provide the controller
with wind shear warnings and alerts, including wind
shear/microburst detection at the airport wind sensor
location, but also provide the location of the hazards
relative to the airport runway(s). It also has the
flexibility and capability to grow with the airport as
new runways are built. As many as 32 sensors,
strategically located around the airport and in
relationship to its runway configuration, can be
accommodated by the LLWAS
−
NE network.
3. Terminal Doppler Weather Radar (TD-
WR).
(a)
TDWRs have been deployed at 45 loca-
tions across the U.S. Optimum locations for TDWRs
are 8 to 12 miles off of the airport proper, and
designed to look at the airspace around and over the
airport to detect microbursts, gust fronts, wind shifts,
and precipitation intensities. TDWR products advise
the controller of wind shear and microburst events
impacting all runways and the areas
1
/
2
mile on either
side of the extended centerline of the runways out to
3 miles on final approach and 2 miles out on
departure. (FIG 7
−
1
−
16 is a theoretical view of the
warning boxes, including the runway, that the
software uses in determining the location(s) of wind
shear or microbursts). These warnings are displayed
(as depicted in the examples in subparagraph 5) on the
RBDT.
(b)
It is very important to understand what
TDWR does NOT DO:
(1)
It
DOES NOT
warn of wind shear
outside of the alert boxes (on the arrival and departure
ends of the runways);
(2)
It
DOES NOT
detect wind shear that is
NOT a microburst or a gust front;
(3)
It
DOES NOT
detect gusty or cross
wind conditions; and
(4)
It
DOES NOT
detect turbulence.
However, research and development is continuing on
these systems. Future improvements may include
such areas as storm motion (movement), improved
gust front detection, storm growth and decay,
microburst prediction, and turbulence detection.
Meteorology
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1
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