Convective Meteorology (Mesoscale Dynamics)

Sensitivities of 1-km Forecasts of Tornadic Supercells to Microphysics Parameterizations, Assimilated Radar Data, and Assimilation Techniques

Derek Stratman

School of Meteorology

26 February 2016, 3:00 PM

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

The aim of this study is to examine the impact of using five different microphysics parameterization schemes, including single-, double-, and triple-moment microphysics, in an efficient high-resolution data assimilation system suitable for nowcasting and short-term forecasting with low latencies. In addition to testing sensitivity to microphysics, the impact of gap-filling radars, variations in cycling and incremental analysis updating (IAU) data assimilation are explored using a variety of verification methods.

On 24 May 2011, Oklahoma experienced an outbreak of tornadoes, including one rated EF-5 and two rated EF-4. The extensive observation network in this area, including the WSR-88D radars, Collaborative Adaptive Sensing of the Atmosphere (CASA) IP-1 X-band radars, Oklahoma Mesonet, and standard surface data, makes this an ideal case for these tests. Additionally, the real-time configuration of the 1-km ARPS, which used 3DVar with cloud analysis via IAU, had success providing a good baseline. ARPS forecasts of 0-2h are verified using point-to-point, neighborhood, and object-based verification techniques. The object-based verification technique uses updraft helicity fields to represent mesocyclone centers, which are verified against tornado locations from three supercells of interest from this event. Varying levels of success in the forecasts are found and appear to be dependent on the complexity of storm interaction, with early forecasts of isolated storms exhibiting the most success. Verification scores indicate the multi-moment schemes tend to aid in better forecasts of the three tornadic storms of interest. Additional results from the other experiments will also be presented.

Convective Meteorology (Mesoscale Dynamics) Seminar Series website