New DevelopmentsJanuary 29th, 2013 at 4:15 pm by Chad Evans under Chad's WLFI Weather Blog
My math of storm timing does not match the models. They have line of storms more like after midnight, but I come up with 9 p.m. to 12 a.m. So, thinking of totally triming back timing. Be prepared for an earlier arrival, as I am now throwing out model data & NOWCASTING.
I have noticed in these cool-season QLCS events that we usually do not get truly severe gusts or tornadoes (gusts 58 mph or greater) unless dew point reaches 60. That is a critical point whereby updrafts reach critical buoyancy to tap into low-level jet wind energy & transfer it to the ground either as a severe gust or tornado. Dew point of 60 or greater usually gives you SURFACE-BASED instability or CAPE, rather than just elevated CAPE. In order to get severe wind to surface or tornado, you need the storm to root near the ground, not 9,000′ up.
Where pockets of dew point reach 60 or greater, that is where severe weather has the best chance of going.
If we can’t reach that, then it may be hard to get any severe weather to the ground.
That said, I am keeping an eye on the dew points which are running 55-58 degrees. We need to watch 60 threshold with what weather stations we have available that are sited in the best places.
IF it were going to be 70 tonight with a dew point of 66 or 67, then this would be moderate risk for us with significant severe weather outbreak of EF2-EF3 tornadoes & gusts of 60-80 mph (like they will get in Arkansas & Mississippi).
Critical pockets of 60-degree dew points have made it as far north as Bloomington & Pontiac, Illinois.