An Evaluation of Mesoscale Model Simulations of An Oscillating Dryline

It is well known that convective initiation may occur in the vicinity of a surface dryline. Contributing factors to initiation such as enhanced temperature and dewpoint temperature gradients, increased lift, and mass and moisture gradients may each be present in varying degrees along the dryline. During synoptically quiescent conditions, the dryline often oscillates east-west across the high plains, with not any or only isolated moist convection. These drylines are excellent candidates for simulations since there are no storm-scale processes to interact with the dryline environment. Previous numerical studies have shown that during these conditions, topography and soil moisture gradients are very two very important controls of the dryline environment. Mesoscale models are now often employed for forecasting dryline motion as their finer resolution should allow better representation of these and other surface features. For this study, simulations were conducted of an oscillating dryline from 14-18 April 2002. The study domain is an approximately 200 square km area centered nearby Lubbock, TX. The two mesoscale models used were the PSU/NCAR MM5 and the CSU/ATMET RAMS; each run with an inner-grid resolution of 6 km and initialized from NCEP ETA model fields. The in-situ measurements of the observed dryline in this case are provided by 30 meteorological observation stations of the West Texas Mesonet. A comparison of model output to the observations is performed through a spatial analysis of dryline position and through calculation of the mean bias and rmse for several meteorological variables.