Aviation Weather Forecasts Based on Advection: Experiments Using Modified Initial Conditions and Improved Analyses.
Environmental research papers Oct 83-Oct 84,
AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA
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Previous experiments had shown that upper-level wind flows could be used to advect surface weather parameters to produce short-range 0-15 hours forecasts. However, to achieve scores better than persistence, allowance had to be made for stationary weather patterns and also for diurnal changes in weather conditions. Two new forecast experiments were prepared and carried out, using data from 12 cases during March 1983. First, data were edited and adjusted to reduce effects of local conditions altitude, surface roughness, and then were advected. Finally, the adjustment was removed. The forecasts using a 500 mb space-averaged flow with modified initial conditions produced improved advection forecasts, with some parameters better than persistence and MOS Model Output Statistics for 2-7 hours. In the second experiment, an improved objective-analysis procedure was introduced, one based on the Barnes approach, which uses one-half degree about 45 km resolution and previous analysis as a first guess. Prior analyses were 1 degree, single pass, Cressman-type analyses. These improved analyses resulted in a somewhat better score for 1-3 hours using a change-advection technique, but were slightly worse at longer periods. Apparently, the small-scale patterns recovered by the improved analyses were largely either short-lived or stationary. These conditions would not lead to better advection forecasts. Further examination revealed that those parameters most difficult to resolve in the objective analyses visibility, ceiling, and wind speed also had the lowest forecast skill scores for persistence. Keywords Aviation forecasting Meteorology Mesoscale analysis and forecasting.