|Tuesday, May 19, 2009 - 4:12PM
2009 Plains tornado season running out of time
The last few model runs keep reaffirming previous thinking about the long-range outlook for the 2009 storm season in the Plains. The ridge out west entrenches itself even further as signs of a 'blocking pattern' set in. Blocking configurations are so named because they are very hard to break, and therefore linger for a long period of time (sometimes for weeks). Spring tornado season in the Plains is a finite period that usually ends when this type of summer-esque pattern shows itself, by mid-June in the average year. With the long-range outlook showing consistent downtime in the Plains through the end of the month (at least), it is not looking good for the rest of the season.
As a result of all this, I'm further lowering my confidence level on a second Plains trip happening this year. Of course, I'll 'never say never', since the atmosphere is known for last-minute curveballs. There is still the chance that the models are wrong and a turnaround could happen after June 1, but I'm beginning to lose any confidence in the chances of that taking place. Most storm seasons are done by early June, and there isn't much of a window now for the pattern to realign itself.
The northern Plains tornado season does ramp up by mid-June, but most years, good events there are fewer in number, widely spaced in time (not many multi-day setups to make a long trip cost effective) and of course require a much longer drive than setups in the southern/central Plains. I almost consider the northern season chances akin to southern Plains non-southwest flow opportunities, IE, a much higher money/miles-per-tornado cost that puts it out of practicality range for those of us with limited budgets. So unless an anomalous string of healthy outbreak setups pop up for the northern territories, I have no plans to observe storms there this year.
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 19|
|No trip #2||68%|