BIG UPDATE

I haven't had enough time to update this blog. But here are the major severe wx events of April:

April 3 - big severe wx outbreak with a couple of tornadoes.
April 10-11 - small event with two very impressive supercells, one over OK, one over AL.
April 13-14 - really had potential with a high risk over TX on the 13th that did not verify.
April 20-21 - tornadoes over the Plains, specifically, NE and the TX Panhandle.
April 23-24 - started out with several discrete and powerful, but widely isolated, Plains supercells. Ended with a high risk bust just to the east over I-35.

Granted, I didn't post a lot on the last two events. But as one can see, it was an active month for severe wx, although not even close to last year.

The limiting factor for this year so far has been the stagnant pattern over Western Europe and the Atlantic, which has been crunching up a fast Pacific jet. The jet is a result of Indian Ocean convection and the associated IO subtropical jet/Siberia polar jet "phasation" (is that even a word, lol?). At any rate, the flow is not as progressive when it punches into the CONUS, so basically a big bowling ball closed low results as the jet energy is forced to crunch up. These big bowling balls tend to not be prolific tornado producers. Case in point: April 24.

WHY DID APRIL 24 BUST?
For those who don't know, April 24, 2007 was predicted to be potentially one of the biggest outbreaks in the Plains in recent years. A big 500mb low was progged to hit a very moist and unstable airmass (the GFS, for instance, had predicted -10 LI's in central OK about a week out, although it did not verify). Many of the ingredients were there. Dr. Greg Forbes of TWC, Larry Cosgrove, among other very good mets were predicting an outbreak on the scale of the intensity of May 3, 1999. An almost unprecedented Day 3 Moderate risk was hoisted by the Storm Prediction Center.

In the end though, it all went bust, as convection formed too early. But why?

IMO, the reason it busted is mainly because the bowling ball closed low which had already stacked by the time. It is fairly common knowledge that a stacked low tends to be less condusive for severe wx. In this case, the dry line pushed very far east as CAA behind it intensified and the low matured and began to stack. Convergence along the dry line intensified, and coupled with strong upper air support, a line formed early and hard.

I think, that perhaps with less instability in the morning, or with some type of earlier convection to stabilize, this could've still ended up being a notable event. Strong instability fostered big anvils, which stablized things, and the convection developed into a line quickly, preventing moist inflow to areas later.

Still though, one tornadic supercell did form along the dryline later that day, a testament to how much potential this setup really had. A high risk was hoisted for central TX later that afternoon, but it mainly busted with few reports in the area. The lack of juxtaposition between the instability axis, the location of initiation, and the low level shear axis probably prevented from supercells which formed there in the afternoon, from being tornadic.

Ironically, the one strong, classic supercell that formed, formed in northern MX and entered deep south TX near Eagle Pass, TX, killing 10 people, 3 in MX, 7 in TX. It had perhaps one of the most impressive radar signatures I've ever seen, along with a monster supercell in rural northwestern KS the night before.