A NUMERICAL-SIMULATION OF THE 7 MAY 1985 MESOSCALE CONVECTIVE SYSTEM

On 7 May 1985 a mesoscale convective system (MCS) developed within a m oderately forced large-scale environment for upward motion and moved i nto the observing network of the Oklahoma-Kansas Preliminary Regional Experiment for STORM (PRE-STORM). The initial region of convective dev elopment occurred outside the PRE-STORM network in a data-sparse area. Simulations using The Pennsylvania State University National Center f or Atmospheric Research(PSU-NCAR) Mesoscale Model are produced using i nitial conditions from two different initialization techniques, static initialization and improved dynamic initialization, to evaluate the a bility of the mesoscale model to reproduce the complex evolution and s tructure of this MCS. The results indicate that, even when including t he special PRE-STORM data in the model initialization process, the num erical simulation that uses the initial condition from the static init ialization fails to simulate the observed evolution of the 7 May 1985 MCS. This is attributed to both the relatively weak large-scale forcin g for upward motion and the lack of adequate mesoscale observations of the low-level moisture distribution and wind field in the Texas panha ndle and western Oklahoma. In contrast, the initial condition from the dynamic initialization approach that uses the results of a continuous four-dimensional data-assimilation technique (nudging) as a first gue ss for a static initialization (both of which include the special PRE- STORM data) produces a successful simulation of the MCS. This simulati on captures remarkably well many of the observed and analyzed mesoscal e features determined from the high-resolution PRE-STORM observing net work data. Threat scores for precipitation amounts and root-mean-squar e errors of sea level pressure are calculated to provide an objective measure of the quality of the simulations.