The use of hourly model-generated soundings to forecast mesoscale phenomena. Part I: Initial assessment in forecasting warm-season phenomena

Since late 1995, NCEP has made available to forecasters hourly model guidan ce at selected sites in the form of vertical profiles of various forecast f ields. These profiles provide forecasters with increased temporal resolutio n and greater vertical resolution than had been previously available. The h ourly forecast profiles are provided for all of NCEP's short-range models: the Nested Grid Model, Era Model, and Mesoscale Eta Model. The high-resolut ion forecasts aid in the timing of frontal passages, low-level jets, and co nvective initiation. In addition, through time-height cross sections of Ric hardson numbers, forecasters can alert pilots to the potential for clear ai r turbulence several hours to a day in advance. Further, the profiles are u seful in prediction of cloudiness and the dissipation of low-level stratus and fog. Time-height cross sections of wind velocity have proven extraordin arily useful in visualizing and forecasting inversion heights, frontal pass age timing, boundary layer depth, and available environmental and storm-rel ative helicity during convective events. The hourly model forecasts were found to be exceptionally helpful when comb ined with hourly surface observations to produce enhanced real-time analyse s of convective parameters for use in very short term forecasting. High-res olution analyses of lifted index, CAFE, convective inhibition, moisture flu x convergence, and 2-h changes in these fields aid the forecaster in antici pating convective trends. The introduction of model forecast error into the se real-time analyses was minimized by using the latest available Era or Me soscale Era Model runs. Therefore, the model data used to enhance the analy ses are typically no more than 6-12 h old.