Convective Meteorology (Mesoscale Dynamics)

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

Brittany Dahl
OU School of Meteorology

18 April 2014, 3:00 PM

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

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. Two sounding ensembles were created by scaling these errors to 10% and 25% of the original magnitude. These soundings were then used to initialize horizontally homogeneous environments for 41 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 intra- and inter-ensemble comparison of the spatial distribution of detected vortices, timing of detections, and vortex strength is conducted, as well as analysis of the relationship between initial environmental conditions and vortex characteristics.

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