Medium Range Forecast Exercise for Tallahassee, Florida

Based on this case, we can come to the following conclusions about the forecasts for TLH for 28 October 2003, based on information from 23 October 2003:

• In the final analysis it appears that all day-5 forecasts on 23 October 2003 failed because
  
  • The two short waves in the westerlies over the eastern Pacific “dug” southward into south Texas as the long wave pattern underwent retrogression, rather than propagating southeastward to reinforce a major trough in the long wave pattern over the east central U. S. as forecast by the GFS.
    
  • Additionally, it seems likely that the residual moisture from Tropical Depression Patricia migrated into the south Texas trough. This system, with its enhanced moisture, propagated northeastward across the Gulf of Mexico giving TLH over an inch of rain on 28 October 2003, a day that was forecast to be sunny and cool.
    
• A medium range forecast (3-5 day) during October for a city along the Gulf coast, such as Tallahassee, is influenced by
  
  • The prevailing long wave pattern,
    
  • The progression of short waves in the westerlies, and by
    
  • The possible input of moisture from a late season tropical system in the Gulf of Mexico, or even the eastern Pacific.
    
• Forecasters should examine model initializations carefully to determine the degree of uncertainty in the model’s initial state.
  
  • They should be wary of model forecasts when the atmosphere is undergoing a major adjustment, such as a retrogression in the long wave pattern.
    
• Finally, they should keep an eye on the tropics for the possible interaction of a weakening tropical system with the ever- strengthening short waves in the westerlies.