Storm Highway by Dan Robinson
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Thursday, May 7, 2009 - 4:03PM

Wavering models making forecasting difficult

By DAN ROBINSON
Editor/Photographer
25 Years of Storm Observing
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Still holding tight here, watching for signs of something worth making a second run out to the Plains. Long-range forecast models have not been performing well this season, making any long-term weather expedition planning nearly impossible. Several times during the past few days, both the GFS and the Euro models have been flip-flopping dramatically between a great western trough and a less-favorable, higher-latitude zonal flow pattern. The latter has actually been showing up more - leading to a lower probability of any trip happening in the next week. The latest two runs (at 00z yesterday and 12z today) do not look good for tornadoes in the Plains for as far out as the models go. Due to the models' poor performance, I have a very low confidence level in speculating out beyond a week. So, I have no choice but to give equal departure date probabilities for the remainder of the month - with the exception of the upcoming week, which gets a lower percentage.

As a matter of fact, the upper air forecast actually favors some expedition days in Kentucky, Ohio and West Virginia next week.

Based on the current outlook, this probability table charts the chance of the second Plains weather expedition starting on a particular date:

2009 Weather Expedition #2 - Departure Date Probability as of May 7
May 7-1212%
May 13-2022%
May 21-3122%
June 1-1522%
No trip #222%

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