14.1 GBVTD-retrieved near-surface axisymmetric vortex structure in a tornado and tornado-like vortices observed by a W-band radar during VORTEX2

Thursday, 8 November 2012: 10:30 AM
Symphony I and II (Loews Vanderbilt Hotel)
Robin L. Tanamachi, CAPS/Univ. of Oklahoma, Norman, OK; and H. B. Bluestein, K. Orzel, S. J. Frasier, and M. Xue
Manuscript (9.7 MB)

As part of the VORTEX2 field campaign, a mobile, W-band Doppler radar collected near-surface observations in an EF-0 tornado near Tribune, Kansas on 25 May 2010 and in tornado-like vortices (TLVs) near Prospect Valley, Colorado on 26 May 2010. In the Tribune case, the observed tornado condensation funnel dissipated and then reformed after a 4-minute gap. In the Prospect Valley case, no condensation funnel was observed, but evidence from the highest-resolution radars in the VORTEX2 fleet indicates multiple TLVs near the surface, some with weak-echo holes accompanying Doppler velocity couplets. The tangential and radial wind component evolution of these vortices, from genesis to decay, are investigated via Ground-Based Velocity Track Display (GBVTD) analysis of W-band velocity data, which had a range resolution of 30 m and azimuthal resolution of 0.18°. It is found that the appearance and disappearance of the condensation funnel on 25 May coincides with fluctuations in the retrieved axisymmetric winds. It is also found that the 26 May TLVs exhibit similar axisymmetric tangential velocity structure to the 25 May tornado, but have smaller peak tangential winds overall. Implications for the conventional definition of a tornado will be discussed.
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