STORM2K

How come this year, tornado numbers in the USA are so low? This boggles my mind, how can something just prevent them from happening when they should? It is also really wierd how Canada has had above average tornado confirmations. I believe it is about 75 now. I got around to counting all the tornado reports of this year for a few tornado alley states...

2005 Tornado reports in Oklahoma
Total: 18

June 16: 1
June 9: 3
June 5: 2
June 4: 1
May 24: 1
April 21: 1
April 10: 1
April 5: 1
March 21: 7

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2005 Kansas tornado reports:
Total: 125

September 13: 3
September 5: 1
August 19: 7
August 17: 1
July 3: 5
June 30: 5
June 29: 1
June 16: 1
June 15: 2
June 9: 28
June 8: 1
June 4: 9
June 3: 7
May 30: 1
May 28: 1
May 11: 7
May 10: 1
April 21: 15
April 10: 18
April 5: 9
March 21: 2

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Nebraska tornado reports
Total: 66

September 12: 1
July 5: 1
June 17: 16
June 15: 1
June 6: 5
June 4: 2
May 17: 1
May 12: 1
May 11: 7
May 10: 14
May 7: 12
April 21: 1
April 18: 3
March 30: 1

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South Dakota Tornado Reports
Total: 17

July 7: 1
June 26: 3
June 25: 1
June 13: 2
June 7: 8
June 4: 1
May 8: 1

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So wierd. Anyone have an answer?

There is a tendency for tornado frequency in the Alley to be down in Springs following a Niño winter.

Steve

Wisconsin's total is up to 60 for the year, following two additional tornadoes the other day. This blows away the old yearly total, and conditions look ripe for severe weather again next week. Not a quiet year in the upper Midwest!

Scostorms,

The May-July synoptic setups were starkly different between 2004 and 2005. In 2004, there was a predominant strong trough in central Canada and dual ridges--one over Alaska and another over the Southeast. Clashes between sharply contrasting air masses were favored in such a setup.

May-July 2004 500 mb Height Anomalies:


In the comparable period this year, there was only a weak predominant trough across northern Canada and a ridge that predominated in eastern Canada. This setup was much less favorable for the kind of clashes in air masses that typically spark tornadic activity.

May-July 2005 500 mb Height Anomalies:


The fact that spring-summer 2005 preceded a weak El Niño might well have led to the evolution of a pattern that favored reduced tornadic activity.