[AFPhys]

It looks like Ike is moving out so rapidly that it won't be interacting (so far) in a way that will kick up MAJOR amounts of violent weather, at least. That was a real possibility as I read it yesterday. Today most of that likelihood seems to have been dissipated. I hope that holds true - I'm on Ike's exit route, as are quite a few FReepers, including you.

Here's the current tornado watch map (It will update when page is loaded)

http://www.spc.noaa.gov/products/watch/validww.png

[jeffers]

http://www.spc.noaa.gov/products/wwa/

http://www.spc.noaa.gov/products/outlook/day1otlk.html

So far, the projected severe weather area for today has extended north and east, now comprising a crescent around 1500 miles long and 300 miles wide, from southern Louisiana, to western Maine.

The risk has not been elevated above Slight, which usually means “some homes will be damaged in your state, and a few people might die”. Moderate Risk means “this will make the news tomorrow, because we expect severe storms to kill some people in your state”. High Risk means “find a hole and crawl inside.”

The major forcing mechanisms that produce severe weather, cold front, warm moist air, cold Canadian air, an jet stream are already in play, but there are some subtler mechanisms, vorticity, lifted index, CAPE, insolation, etc. that are not so clearly in favor of severe development.

Simply put, the lower third of the atmosphere is strongly conducive to producing tornadoes and high straight line winds. The middle third is counter-productive towards rotating and strong storms, and the upper third of the atmosphere has strong support for tornadic storms. The strongest, longest lived tornadoes require support at all three levels.

You probably WILL see short lived severe storms throughout the warned area, embedded in a dynamic, long lived squall line, but if any cells punch through the middle unfriendly layer to reach up to jtstream support, look out for long lived supercells with sustained tornadic activity.

More than anything else we’ll need to watch how the day develops. The middle third of the atmosphere is unfriendly because it’s warm enough to inhibit sustained updrafts. If the sun comes out ahead of the cold front, the lower layer air will be hotter and then the middle layer won’t seem so unfriendly, allowing some storms to reach up for jet support.