Extreme vertical winds measured by dropwindsondes in hurricanes

Since the operational use of Global Positioning System drowindsondes in hurricanes commenced in 1997, 26 instruments have measured upward motions strong enough to cause the instrument to rise substantially before resuming its descent. This includes the observation of 25 m/s updrafts in Hurricane Isabel (2003) that caused an instrument to rise nearly 500 m and remain suspended for more than 90 s. The 26 observations will potentially be augmented by further observations from the unusually active 2005 hurricane season.

Previous studies have related the Isabel observation to an eyewall misovortex. These additional observations, combined with aircraft flight-level and airborne reflectivity and Doppler data (when available) will help to elucidate the structures responsible for these extreme winds. Special consideration will be given to the possibility that such vertical motions can cause strong horizontal motions associated with the features to reach the surface and do damage to life and property. Proposals for the mechanism for the formation of these features, especially the superintensity theory of Persing and Montgomery, will be presented.