Today's operational numerical models continue to struggle with correct prediction of the moisture content of the return flow airmass over the Gulf of Mexico after a cold-air outbreak. Errors in forecasted surface winds and the use of non-varying sea surface temperatures are identified as possible influences on the incorrect moisture forecast (Lewis 2007). Cold-air outbreaks are associated with significant changes in sea surface temperature over a wide region of the Gulf of Mexico. This cooling of the sea surface temperature by as much as several degrees relative to the initial temperature field should be reflected in differences in the air-sea fluxes of latent and sensible heat, which then may be manifested in different boundary layer temperature and humidity structures. Thus it is speculated that the inclusion of this variation in sea surface temperature will influence the nature of the return flow airmass.

In this talk we will present the effects of a realistic time-varying sea surface temperature on the atmospheric conditions leading to the return flow over the Gulf of Mexico The WRF (Weather Research and Forecasting) version 3.0 atmospheric model at high resolution (~4 km) is used to look at past cases of cold-air outbreaks and return flow over the Gulf of Mexico during the November-March time period. The forecast length is approximately 10 days for each case in order to capture the full cycle of the cold-air outbreak and subsequent return flow in the model simulation. Several simulations are performed with several different SST datasets prescribed for initial conditions. These SST datasets are then held constant throughout the forecast period in some cases, while in the other cases the SST is updated daily. This strategy is used in order to better gauge the affect of the SST over the Gulf of Mexico on the model simulation. Particular attention is given to subsequent changes in winds, fluxes, temperature profiles, moisture profiles, and precipitation in the model output. The results are presented with the ultimate goal of working towards a fully coupled, high resolution WRF/HYCOM (HYbrid Coordinate Ocean Model) atmosphere/ocean modeling system over the Gulf of Mexico.