Originally posted by nickgrillo+--><div class='quotetop'>QUOTE(nickgrillo)</div>
<!--QuoteBegin-Andy Wehrle
Yeah...what I meant was that there is a good possiblity of a near-surface stable layer, and the tornado threat is conditional on there NOT being one.
With the strength of the LLJ I wonder if the SPC did not include the "strong tornado" wording with last November's Evansville event in mind. If I recall correctly the strong jet fueled a lone significant tornadic supercell despite the generally low instability.
Actually, I'm concluding a substantial case study about the "EVV" (and surrounding) tornadoes... There wasn't low instability at all. If you modified the Lincoln ob sounding to the 0700 UTC (about 40 mins prior to tornadogenesis) EVV sfc conditions... You got a solid ~2000 J/kg of CAPE. Additionally, if you go back to SPC mesoanalysis graphics to the timeframe of the tornadoes, you will see a jump in 3km CAPE (low-level CAPE) which implied the deep moisture and the lack of CIN. And in addition, you also had significantly low LFC and LCL heights.
There was an area of very strong 300mb divergence overhead during the tornado -- which helped lower surface pressure and created a mesolow analyzed at PAH at 0700 UTC. Sorry to hi-jack the thread, but I've been doing a lot of research on that day this past week... LOL...
However, with the presence of a 50-60 southwesterly LLJ, you will definitely get some substantial low-level moisture advected well into IL and IN tomorrow (and at least moderate boundary layer instability developing in central IL).[/b]