Dynamical Analysis of Splitting Supercells on 10 May 2010 Using a High-Resolution Ensemble

Jonathan Labriola* and Ming Xue, Nathan Snook, Youngsun Jung
University of Oklahoma,CAPS

Though relatively rare, left-splitting storms are known to produce a disproportionately high number of severe hail reports. On 10 May 2010, a left-splitting supercell occurred over southwestern Oklahoma, producing a swath of severe hail, as well as two anticyclonic tornadoes. Accurate numerical prediction of left-moving supercells requires accurately capturing the sheared environment in which they develop, making such prediction is difficult. To predict the splitting storms of 10 May 2010 and correctly reproduce the near-storm environment, multiple data sources, including NEXRAD and CASA radar data, Mesonet surface observations, as well as radiosonde and wind profiler data, are assimilated into a set of 40-member ensemble forecast experiments with 500 m horizontal grid spacing using the ARPS EnKF system.

Ensemble members that predict splitting- and non-splitting supercells are analyzed to determine which kinematic variables most strongly influence the storm split. Results suggest ensemble members that produce a splitting storm have higher 0-6 km bulk shear, influenced by a strong dryline boundary upwind of the storm. The subsequent maintenance of the left-moving storms is also considered, with a focus on determining which environmental features correspond to the maintenance of the left-moving supercells. Members that forecast long-lived left-splitting storms have negative 1-3km SRH values in the storm inflow region, in agreement with Bunkers (2002). SRH is highly sensitive to the storm motion vector—a data-mining-based storm tracking method is found to produce a more representative SRH field than estimation using the methods of Bunkers et al. (2000), helping to distinguish environments that produce strong and weak splitting storms.

*email: j.labriola@ou.edu
*Preference: Poster