13 Updates to a mobile radar climatology of supercell tornado structures and dynamics

Monday, 26 September 2011
Grand Ballroom (William Penn Hotel)
Curtis R. Alexander, NOAA/ESRL, Boulder, CO; and J. M. Wurman

Fine-scale-resolution mobile radar observations of supercell tornadoes have been collected by the Doppler On Wheels (DOWs) platform between 1995 and 2010. The result of this ongoing effort is a large observational database spanning over 170 separate supercell tornadoes with a typical data spacing of O(50 m X 50 m X 50 m), updates every O(60s) and measurements within 20 m of the surface extending to several km above the ground. The data used in this study span 1995-2001 and 69 tornadoes along with about four selected tornadoes from 2003-2004.

Stemming from this observational database is an effort to characterize both the structure and dynamics of the high wind speed environments in and near supercell tornadoes. To this end, a suite of algorithms was developed for and applied to the DOW radar observations for quality assurance along with detection, tracking and extraction of attributes associated with the tornadoes.

The integration of observations across tornado cases in the database produced tornado size and intensity distributions revealing a preferred scale and amplitude for tornadoes produced from mesocyclones of supercell thunderstorms while exhibiting a weak negative correlation between the horizontal scale of a tornado vortex core and the peak intensity. Two horizontal scales are apparent in the clustering of intensity observations with the strongest tornadoes on the smaller scale. The observed intensity distribution is contrasted with traditional damage derived intensity estimates of the same tornadoes from a storm report database to highlight the existing low-bias in supercell tornado intensity estimates. Additional tornado structures and evolution are also discussed.

Data analysis work and the DOWs have been supported by NSF grants 0801041 and 0734001.

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