Convective Meteorology (Mesoscale Dynamics)

Multi-Scale Data Assimilation of the 13 June 2010 Tornadic Supercell Storm Environment during VORTEX2

Terra Thompson
OU School of Meteorology

04 April 2014, 3:00 PM

National Weather Center, Room 5600
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

The success of ensemble data assimilation (hereafter DA) at convective-scales is limited by a number of challenges, including the difficulties associated with accurately analyzing mesoscale phenomenon in the storm environment. A promising new technique combines radar DA with simultaneous assimilation of conventional observations, hereafter referred to as multi-scale DA. Multi-scale DA is applied to the 13 June 2010 case during VORTEX2. On 13 June a cold pool from overnight convection created an outflow boundary that was located near the Oklahoma-Texas Panhandle border in the afternoon. New convection developed along a cold front in the Texas Panhandle. The sub-severe convection slowly moved to the northeast and a cell moved over the intersection of the two boundaries, intensified, gained supercell characteristics, and became tornadic. This case represents a complex mesoscale environment and storm evolution that was not captured well with conventional observations or WSR-88D radars. Thus, it is difficult to analyze and predict without the use of multi-scale DA.

A framework for multi-scale DA is developed to improve forecasts of the mesoscale storm environment and convection. The sensitivity to the background ensemble is investigated by comparing the storm environment after four days of DA cycling, to the storm environment initialized on the day of the event. The impacts of hourly multi-scale DA cycling on the day of the event are compared to conventional six hourly analysis cycles. The value of radar DA in hourly DA cycling is also investigated. Lastly, the impact of the storm environment on convective forecasts will be discussed.

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