Diagnosis of 3D Wind Structure of a Tornado Using VTD Analysis

A tornado occurred in 4 May 1999 during the tornado outbreak near Oklahoma City was observed by the Doppler on Wheels located about 4 km from the tornado. Excellent Doppler radar data with high temporal and spatial resolutions were collected with maximum Doppler velocities exceeding 80 m/s.

The purpose of this paper is to attempt to deduce the tangential wind structures of this tornado using the ground-based velocity track display (GBVTD) technique. The GBVTD technique was originally designed to deduce tropical cyclone circulations from single Doppler radar data. It was found that the GBVTD technique can resolve reasonable structures of this tornado. A wave number 3 asymmetric circulation was resolved by the GBVTD technique. Similar to tropical cyclone's structure, the intensity of the circulation decreases with altitude while the radius of maximum wind increases with altitude. This may be the first successful attempt to resolve the asymmetric tangential circulation of a tornado from single Doppler radar data.

The evolution and structure of this tornado over a 20-min period will be shown in the conference.