Abstract
Results are presented from a nine-hour limited area fine mesh (35 km) mesoscale model simulation initialize with SESAME-AVE I radiosonde data for 10 April 1979 at 2100 GMT. Emphasis is on the diagnosis of mesoscale structure in the man and precipitation fields.
The model simulated most of the life cycle of a propagating mesoscale short wave/precipitation band (≈250 km wide) which developed from a dry low-level (700 mb) mesoscale short wave trough in the initial state. The short wave, which was supported initially by balanced winds, was retained by the model, propagated around a synoptic scale trough from Oklahoma to Nebraska, while initiating and organizing precipitation into a mesoscale band along the trough axis. The short wave and precipitation propagated northward together at about 18 m s−1 The onset of precipitation was accompanied by a decrease in width of the short wave. The system displayed distinctive vertical structure including downwind tilt with height. The short wave precipitation band verified well with a similar band evident in NMC hourly radar summaries in terms of location, rate of movement and spatial dimensions.
Along the Texas/Oklahoma border, independent of the short wave, convective precipitation formed several hours into the simulation and was organized into a narrow band suggestive of the observed 10 April squall line. The orientation and location of model convective precipitation were generally consistent with observed convective weather areas over Texas and Oklahoma.
The good results of model simulation are attributed to a combination of comprehensive model physics, fine grid resolution and subsynoptic scale initial data.
