Are GFS 500hPa Forecasts More Consistent when the Energy is over land?

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Sunday, 2 February 2014
Hall C3 (The Georgia World Congress Center )
Eswar R. Iyer, Iowa State University, Ames, IA

Forecasts during the winter are always very hard to make because a 50 mile error can mean the difference between snow and rain. The run to run consistency of the GFS model will be analyzed to see if the GFS has more run to run consistency (in the forecast location of the main 500mb low over the central U.S.) when the main area of 500mb vorticity is over the Pacific Ocean or inland. Cases from November-April will be analyzed. Previous runs of the GFS will be analyzed to see if the consistency does indeed increase when the energy crosses ashore. I will track the forecast location of the 500mb low in the central U.S. for several different cases. Two things will be reported: 1) whether the GFS is indeed more consistent when the main 500mb trough is over land and 2) whether there is a more rapid decrease in the forecast error in the GFS right as the 500mb trough and vorticity cross ashore relative to the average decrease in forecast error due to the event getting closer in time. To numerically analyze my results, a statistical test will be used.