An investigation of the tornadic stage of the Goshen County, Wyoming, supercell of 5 June 2009 using EnKF assimilation of mobile radar data collected during VORTEX2

Mobile radar velocity observations collected on 5 June 2009 during VORTEX2 are assimilated into a supercell simulation using the Advanced Weather Research and Forecasting model and the ensemble Kalman filter (EnKF) technique. The EnKF analyzes heterogeneous multi-platform data so that a thorough diagnosis of mesocyclone-scale processes relating to tornadogenesis, maintenance, and decay can be performed. Observations are assimilated at 2-minute intervals into a 50-member ensemble with horizontal model grid spacing of 500 m.

We present results updated from those shown at the 25th Severe Local Storms Conference. Trends of the single-Doppler-estimated tornado intensity are compared to the EnKF representation of the parent supercell. Emphasis is placed on the buoyancy of the surrounding low-level outflow air, the strength of the low-level mesocyclone-scale circulation, and the relative placement of the tornado to the mid-level updraft and mesocyclone. The trajectories of parcels located in the low-level mesocyclone are traced backward and forward from times representative of the formation, mature, and dissipation stages of the tornado to determine if origins of low-level vertical vorticity differ throughout its lifecycle and to assess the evolution of connections between updrafts near the surface and aloft. The thermodynamic history of parcels located just west, south, and southeast of the tornado are evaluated to diagnose origins of a surging rear-flank downdraft, a feature believed to be important to the formation and maintenance of this tornado.