Multi-Doppler and polarimetric analysis of a tornado and rear-inflow jet

The Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) is funded by the National Science Foundation with the objective to create low-power, low-cost, short-range (X-band) radars that can be deployed on cell-phone towers.  Multiple CASA radars will be deployed collectively, together comprising an integrated network with the radars operating collaboratively and adaptively, sensing when and where end-user needs are greatest.  A demonstration testbed of four CASA radars was deployed in Oklahoma in 2006, and since that time has operated each spring and fall during convective events.  Each radar has a range of 40 km, a bandwidth of 1.8 degrees, dual-polarization capability, and rapid update capacity (< 1 minute refresh).

On 13 May 2009, a thunderstorm complex associated with a cold front moved south through the CASA network. A tornado rapidly developed in an embedded supercell on the northeast side of the complex. The lifecycle of the tornado was sampled by two CASA radars and caused up to EF-2 and over 19 km of damage near the town of Anadarko. Several other areas of rotation were visible on CASA, but none of which produced confirmed tornado damage. Once the tornado dissipated, a strong rear-inflow jet (> 90 mph) developed in the center of the complex. The rear-inflow jet was sampled at low elevations by several CASA radars. This study will analyze both multi-Doppler and dual-polarimetric attributes of this complex using data from the CASA and NEXRAD networks and wind fields from ARPS 3DVAR analysis.  In particular, the possible relationship between the tornado and rear-inflow jet will be discussed.