School of Meteorology (Defense)

Sensitivity of Vortex Production to Small Environmental Perturbations in High-Resolution Supercell Simulations

Brittany Dahl
OU School of Meteorology

21 July 2014, 3:00 PM

National Weather Center, Room 5820
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

Sensitivity of Vortex Production to Small Environmental Perturbations in High-Resolution Supercell Simulations
Studies have indicated that errors in the initial conditions of atmospheric models propagate toward both larger and smaller scales of motion, which limits the range of practical predictability in numerical forecasts. With short-term, storm-scale prediction to play an increasingly important role in tornado warning operations (e.g., Warn-on-Forecast), it is beneficial to understand the relative impact of errors in the background mesoscale environment on storm features associated with tornadogenesis.

To investigate the effect of mesoscale errors on low-level mesocyclone-scale vortex development in simulated supercells, perturbations were randomly drawn from typical 1-hour forecast errors observed from the 13 km RUC in Cintineo and Stensrud (2013) and applied to the 29 May 2004 Geary, OK sounding. Three sounding ensembles were created by scaling these errors to 10%, 25%, 50% of the original magnitude. These soundings were then used to initialize horizontally homogeneous environments for 61 idealized simulations at a resolution of 100 m. The vortex detection and classification (VDAC) algorithm outlined in Potvin (2013) was used to identify vertically continuous mesocyclone-scale vortices. An inter-ensemble comparison of the spatial distribution of detected vortices, timing of detections, and vortex strength will be presented, along with analysis of the relationship between initial environmental conditions and vortex characteristics. Finally, a case study using selected ensemble members to examine possible impacts of the environment on storm-scale processes will be discussed.

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