Andy Wehrle
EF5
Re: early
I've had a lot of time to study "high risk climatology" while compiling my archive. High risks are fairly frequent in April (it's only in the last 2 years that May has stolen the show).
April high risks seem to be more prone to busting, or verifying only partially; but when they do verify they do so with a vengeance.
Some good recent examples of "partial verification" would be April 6, 2001, where a squall line developed with very little tornadic activity; April 11, 2001; where the high risk included Iowa, Illinois and Wisconsin but only the Iowa part verified; and April 6, 2003; where there was lots of hail and wind but only a few tornadoes (a MDT risk would have sufficed).
Of course you have only to look at lists of historical infamous tornadoes to learn what happens when April high risks do verify...April 26, 1991; April 19, 1996; April 8, 1998; April 16, 1998...etc. Not to mention April 3, 1974, which would certainly have been a high risk had the SPC issued convective outlooks in the modern format.
March high risks are more infrequent, usually because the instability is marginal but kinematic fields are very strong. Fast-moving squall lines are typical (March 8, 1999 and March 4, 2004) but when tornadic supercells can develop they can be just as bad as April outbreaks (March 13, 1990, March 27, 1994).
http://sphs.angeltowns.net/A_R_Wehrle/highrisk.html
I've had a lot of time to study "high risk climatology" while compiling my archive. High risks are fairly frequent in April (it's only in the last 2 years that May has stolen the show).
April high risks seem to be more prone to busting, or verifying only partially; but when they do verify they do so with a vengeance.
Some good recent examples of "partial verification" would be April 6, 2001, where a squall line developed with very little tornadic activity; April 11, 2001; where the high risk included Iowa, Illinois and Wisconsin but only the Iowa part verified; and April 6, 2003; where there was lots of hail and wind but only a few tornadoes (a MDT risk would have sufficed).
Of course you have only to look at lists of historical infamous tornadoes to learn what happens when April high risks do verify...April 26, 1991; April 19, 1996; April 8, 1998; April 16, 1998...etc. Not to mention April 3, 1974, which would certainly have been a high risk had the SPC issued convective outlooks in the modern format.
March high risks are more infrequent, usually because the instability is marginal but kinematic fields are very strong. Fast-moving squall lines are typical (March 8, 1999 and March 4, 2004) but when tornadic supercells can develop they can be just as bad as April outbreaks (March 13, 1990, March 27, 1994).
http://sphs.angeltowns.net/A_R_Wehrle/highrisk.html
