microburst

(redirected from Dry Microburst)
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Related to Dry Microburst: downburst, Macroburst

microburst

[′mī·krō‚bərst]
(meteorology)
A downdraft with horizontal extent of about 2.5 miles (4 kilometers) or less, associated with atmospheric convection, often a thundershower.

microburst

microburstclick for a larger image
An aircraft flying from A to F will experience strong headwinds at positions A and B. It will experience increasing tail winds at position D and E. There would be downdraft at positions B, C, and D. The maximum intensity of downdraft will be at position C.
The strong downdraft that spreads horizontally just above the ground to form a sharply defined gust front. An aircraft approaching this microburst or gust front may encounter a headwind followed by a strong downdraft and finally end up with a strong tailwind. The area of microburst extends from 3000 to 10,000 ft (1–3 km) and lasts from to 5 to 15 min. An intense microburst could induce wind speeds as high as 150 knots. Microbursts are normally associated with thunderstorms, but there are also “dry microbursts.” In these dry microbursts, precipitation falling from the thunderstorms into the relatively dry air of the lower atmosphere evaporates readily, and the large negative buoyancy thus produced accelerates the air downward, entraining more very dry air. No precipitation reaches the ground, but a microburst wind shear occurs. Airports equipped with an LLWAS (low-level wind-shear alert system) “network expansion,” LLWAS systems integrated with terminal Doppler weather radar (TDWR), and TDWR systems can detect microburst alerts and wind-shear alerts. Controllers will issue the appropriate wind-shear alerts or microburst alerts (e.g., “Runway 28 arrival microburst alert, 45 knot loss 3 mile final”).
References in periodicals archive ?
Conversely, without any associated precipitation, dry microbursts present almost no visual clues of their presence.
At airports located in Western states, like McCarran Airport, the existing microwave TDWR can fail to detect significant dry microbursts as well as frontal passage events in the airport terminal area.
All microbursts contain moisture as they form, but dry microbursts have their moisture evaporate during the downdraft before reaching the earth's surface, making them extremely difficult to detect.