P3.27
An assessment of global models ability to accurately forecast downstream extra-tropical cyclone development in the southern hemisphere winter
Matthew A. Lazzara, Univ. of Wisconsin, Madison, WI; and J. G. McLay and S. G. Decker
This study uses Antarctic composite satellite imagery to assess the skill of two global models in forecasting a vigorous extra-tropical cyclone downstream development event in the southern hemisphere winter. The study addresses two significant factors that influence the numerical forecasting of southern hemisphere flow: the active occurrence of downstream baroclinic development and the sparsity of observations. The presence of vigorous downstream development implies that the downstream dispersal of energy by an extratropical cyclone can lead to long-lived coherent wave packets, or baroclinic wavetrains, that influence locations far downstream of the cyclone. The sparsity of observations throughout the southern hemisphere limits the accuracy of numerical model analyses and the numerical forecasts that are derived from them, and hence the ability of the models to precisely predict downstream development. In this study, energetics diagnostics are performed on upper air analyses and forecasts from the MRF and UKMET global models every 12 hours over a 3 to 5 day period. These diagnostics offer a convenient and effective way of isolating the forecast locations of developing downstream disturbances. The energetics diagnostics are then overlaid on Antarctic composite infrared and water vapor satellite imagery made from GOES, Meteosat, GMS, NOAA and DMSP satellites. This allows a comparison of the forecast locations of developing downstream vortices and other synoptic features with the actual locations of developing downstream disturbances seen in the satellite imagery. The skill of each of the models in capturing the location of the downstream development is then described. The study also illuminates the relationship between the energetics features and the cloud structures observed in the satellite imagery.
Poster Session 3, Operational Applications
Tuesday, 16 October 2001, 9:15 AM-11:00 AM
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