Hey guys,
Just stumbled across this post as well. AWESOME stuff. I've also read the official report and I believe there was a "double dry-line" set up in place which is not uncommon in situations such as this (in Australia). I know of at least 2 other instances of such events (with Sept 29, 1996 being one of them). Basically a trough (quasi-dryline) sets up to the east of the main trough...without thinking about it in any detail, i'm not sure what mechanism allows this to occur. DP's on this day to the east of the quasi-dryline were in excess of 20C (I think I recall even as high as 22C), whereas to the west of the quasi-dryline the DP's were in the mid-teens (say 16C). Then the main dryline further W sees the DP's drop to the low single figures W of this feature. Also, the surface winds on the eastern side of the quasi-dryline are generally north to north easterly (maybe even easterly depending on the position of the surface low), whereas west of the quasi-dryline, the surface winds are more north westerly with westerly or even south westerly winds following the main dryline. As you can see, this creates conditions which highly favourable for severe convection east of the quasi-dryline with greater turning in the lower levels and also much higher DP's allowing for greater instability.
Storms can and often will develop on the main dryline as well but these are less likely to be supercellular/tornadic given the more linear shear, however, they can still pack quite a punch as the upper levels are usually more unstable further back to the west nearer to the upper level low/cold pool and the shear is still quite strong.
And just to make things interesting, in this case where there is such a strong upper level low/cold pool, you may even get storms "in" the cold pool as well given that surface temperatures would be quite tasty in January and there may be enough residual moisture left over from storms to kick off more.
All bets are off when we get another set up like this. BRING IT ON!
Macca
