P3.13
Terrain-induced wind shear during the passage of Typhoon Utor near Hong Kong in July 2001
S.Y. Lau, Hong Kong Observatory, Kowloon, Hong Kong; and C. M. Shun
An outer rainband of Typhoon Utor brought gale force winds, severe windshear and turbulence to the Hong Kong International Airport (HKIA) in July 2001, resulting in significant disruptions to the air traffic. The Terminal Doppler Weather Radar (TDWR) revealed a striking Doppler velocity pattern extending over the airport area, with streaks of low and high-speed flow originating downwind of mountains which rise to nearly 1 km to the south of the airport. Advance warnings of severe windshear and turbulence were issued with the aid of the TDWR.
At the height of the stormy weather, commercial aircraft penetrating the streaks recorded rapid windspeed changes exceeding 15 m/s in 25 s. Analysis of on-board flight data showed that very strong downflows accompanied these rapid wind changes.
This paper presents the TDWR observations obtained during the episode and compares them against the on-board data from commercial aircraft to elicit a visualization of the three-dimensional structure of the low- and high-speed streaks. Implications on the operational warning of terrain-induced windshear will be discussed.
| Figure 1 TDWR radial velocity at 2.4-degree elevation at 1341 UTC 6 July 2001. The red boxes mark the airport's 3-mile approach and take-off area. Three streaks of high-speed flow (marked I, II, III) extended downwind of the complex terrain of Lantau to affect the approach area. | Figure 2 Wind direction and speed measured on-board a commercial aircraft as it penetrated the streaks (marked I, II, III in Figure 1) on approach to HKIA. The aircraft eventually had to undertake a go-around at 1344 UTC. |
Poster Session 3, Topographic Flows (with Coffee Break)
Thursday, 20 June 2002, 2:45 PM-4:30 PM
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Extended Abstract (388K)