SPC's First Use of New Svr Wx Probabilities

[Andy Wehrle]

Upgraded from 5% T and 15% wind on the 0600Z outlook. I wonder if they are really seeing a higher threat or if they just wanted to test 'em out?

Note: Please discuss the possible meteorological reasons for the probability increase in today's Map Room thread.

EDIT: Redid image source URLs to retain the relevant graphics.

 

[Skip Talbot]

When SPC described the probability changes they said it was to accomodate a trend in increasing reports over recent years. So although it looks like a significant upgrade in the probabilities to us, perhaps these increased percentages are only to better correspond with storms reports and will be commonplace from now on. Ie. the 10% will now be equivalent to the 5% and so on...

 

[Rich Thompson]

Skip,

You'll probably see a fair number of 10% tornado areas this spring, but the larger probabilities (45-60%) should remain relatively uncommon in outlooks. Perhaps a bigger change will be reverting to a categorical threshold that is more like 2004 than 2005. In other words, not quite as many MDT risks as last year.