18th Conference on Weather and Forecasting, 14th Conference on Numerical Weather Prediction, and Ninth Conference on Mesoscale Processes

Wednesday, 1 August 2001: 9:40 AM
Assimilation and forecasting experiments on supercell storms. Part II: Experiments with WSR-88D data
N. Andrew Crook, NCAR, Boulder, CO; and J. Sun
We have performed a number of assimilation and forecasting experiments on long lived supercellular convection. Both simulated data and observed radar data experiments have been performed. The simulated data experiments are described in Part I of this two-part presentation. The experiments with observed radar data concentrate on a tornadic supercell that occurred during the CASES experiment near Wichita, Kansas in May of 1997. This supercell developed in an environment of strong shear and moved at approximately 30 degrees to the right of the mean wind (measured between the surface and 5 km). The goal of this study is to examine the mechanisms that control the motion and evolution of this storm.

The primary data source used in this study is the WSR-88D radar located near Wichita. Radial velocity and reflectivity fields have been assimilated into a storm-scale model using a 4DVar adjoint technique. Short term (90 minute) forecasts are then performed based on the initial conditions retrieved by the adjoint method. After some tuning of the model parameters and environmental sounding, simulations have been performed which successful forecast the storm's longevity as well as its speed and direction of motion. At the Conference we will describe these experiments and show the sensitivity of storm evolution to model parameters and environmental conditions.

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