AIM 

4/20/23

 

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Meteorology

(c)

TDWR also provides a geographical situation display (GSD) for supervisors and traffic management

specialists for planning purposes. The GSD displays (in color) 6 levels of weather (precipitation), gust fronts and
predicted storm movement(s). This data is used by the tower supervisor(s), traffic management specialists and
controllers to plan for runway changes and arrival/departure route changes in order to both reduce aircraft delays
and increase airport capacity.

4. Weather Systems Processor (WSP).

(a)

The WSP provides the controller, supervisor, traffic management specialist, and ultimately the pilot,

with the same products as the terminal doppler weather radar (TDWR) at a fraction of the cost of a TDWR. This
is accomplished by utilizing new technologies to access the weather channel capabilities of the existing ASR

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radar located on or near the airport, thus eliminating the requirements for a separate radar location, land
acquisition, support facilities and the associated communication landlines and expenses.

(b)

The WSP utilizes the same RBDT display as the TDWR and LLWAS, and, just like TDWR, also has

a GSD for planning purposes by supervisors, traffic management specialists and controllers. The WSP GSD
emulates the TDWR display, i.e., it also depicts 6 levels of precipitation, gust fronts and predicted storm
movement, and like the TDWR GSD, is used to plan for runway changes and arrival/departure route changes
in order to reduce aircraft delays and to increase airport capacity.

(c)

This system is installed at 34 airports across the nation, substantially increasing the safety of flying.

5. Operational aspects of LLWAS, TDWR and WSP.

To demonstrate how this data is used by both the controller and the pilot, 3 ribbon display examples and their
explanations are presented:

(a) MICROBURST ALERTS

EXAMPLE

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This is what the controller sees on his/her ribbon display in the tower cab.

27A MBA 35K

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 2MF 250 20

NOTE

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(See FIG 7

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18 to see how the TDWR/WSP determines the microburst location).

This is what the controller will say when issuing the alert.

PHRASEOLOGY

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RUNWAY 27 ARRIVAL, MICROBURST ALERT, 35 KT LOSS 2 MILE FINAL, THRESHOLD WIND 250 AT 20.

In plain language, the controller is telling the pilot that on approach to runway 27, there is a microburst alert on
the approach lane to the runway, and to anticipate or expect a 35 knot loss of airspeed at approximately 2 miles
out on final approach (where it will first encounter the phenomena). With that information, the aircrew is
forewarned, and should be prepared to apply wind shear/microburst escape procedures should they decide to
continue the approach. Additionally, the surface winds at the airport for landing runway 27 are reported as
250 degrees at 20 knots.

NOTE

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Threshold wind is at pilot’s request or as deemed appropriate by the controller.

REFERENCE

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FAA Order JO 7110.65, Para 3

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8b2(a), Air Traffic Control, Low Level Wind Shear/Microburst Advisories.