Convective Meteorology (Mesoscale Dynamics)

Ensemble Prediction of Splitting Supercells on 10 May 2010

Jonathan Labriola

School of Meteorology

29 January 2016, 3:00 PM

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

Though rare, left-splitting storms are known to produce a disproportionate 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. Long-lived left-split supercells are relatively uncommon; accurate numerical prediction of such storms requires capturing the sheared environment in which they develop, making prediction difficult. Furthermore, left-moving supercells have been found to cause a disproportionate number of hail reports. To predict the splitting storms of 10 May 2010 and their environment, multiple data sources, including NEXRAD and CASA radar data, Mesonet surface observations, as well as radiosonde and wind profiler data, were assimilated into a set of 40-member ensemble forecast experiments with 500 m horizontal grid spacing run using the ARPS EnKF system.

Practical predictability of the left-splitting storm is investigated, along with the forecast sensitivity to the choice of a single moment (LIN) or double moment (MY2) microphysical scheme. Overall, the MY2 ensemble skillfully predicts the left-splitting storm for lead times of up to 30 minutes; the LIN ensemble is skillful only at shorter lead times and produces a less favorable wind shear environment. Storm relative helicity (SRH) in the near storm environment is analyzed; SRH is highly sensitive to the storm motion vector, and varies substantially due to the assumptions used to obtain it. The storm tracking method is found to produce a more representative SRH field than the Bunkers method, helping to distinguish environments that produce strong, weak, and no splitting storms.

Convective Meteorology (Mesoscale Dynamics) Seminar Series website