Chasing the Wind

Today's date is April 6th, 2006. Five years ago today, I chased my first high risk in western Oklahoma. Really, the only thing similar between that day and this day is that the highest SPC categorical risk is the same. That day featured a very thick cirrus canopy that inhibited daytime heating for the vast majority of the day. That will not be the case today, as a very pronounced mid-level dryslot rotates around the base of the upper trough. Even looking at this trough on satellite, it looks like a doozy. Classic comma head appearance---it just looks like it wants to eat something!

The days leading up to now were filled with much uncertainty about whether or not today would be a big day. Most of the storm chasing community knew there was some potential for today, if things shaped up nicely. However, doubts about the position of the dryline, the quality of moisture return, and storm motion prevented us Oklahoma chasers from getting too excited. But, last night, the models began their westward trend and our optimism began to grow.

Today, I am focused on a few things (forecast wise). First of all, I’m monitoring the dewpoint temperatures to see if they will rise to the values progged by the RUC model. RUC has forecasted a plume of mid-60s Tds all the way up into NE OK. Should this occur, CAPE would become quite large and the tornado potential would increase markedly. However, models have overestimated the surface dewpoints for the last few systems, so I’m very skeptical of such a forecast. Nevertheless, lower 60s dewpoints should be sufficient for some nasty storms.

The next item on the forecast list is the potential for an outflow boundary. As I write this, elevated showers and thunderstorms are rapidly sweeping across Oklahoma from border to border. The showers are favorably timed (i.e. they shouldn’t negatively impact daytime heating), so the outflow boundary should have plenty of time to cook under the early April sun. Of course, the impact is three-fold (as usual). First, it will enhance vorticity (because of its inherent baroclinicity) via density differences across the boundary (i.e. warm air rises, cold air sinks). This will create a horizontal circulation that can then be tilted and stretched into the vertical (where you need spin when you want a tornado). Second, it will lower LCL heights (on the north side of the boundary), which has been shown to be very favorable for the development of tornadoes. Third, it will create a focus for convergence and storm development (parameters are great, but you still need a storm!). So, all in all, this is a very positive development in our quest for the ever-elusive tornado.

Because of these favorable developments, I expect the high risk will be expanded to include NE OK into SW MO. Personally, I feel that (other than storm motions) the most favorable region for the development of strong, long-lived tornadoes is in far SE KS, NE OK, and into SW MO. Here, storms will remain more isolated and will have access to high-octane moisture. The only negative here (as compared to further north) is that pressure falls will not be as significant. However, this should not preclude the development of very dangerous tornadic supercells.

Target: Bartlesville, OK

EDIT: The newest RUC looks *awesome*. If this were to verify, I'd expect an outbreak of tornadoes. However, the RUC still seems to be a bit bullish on Tds (compared to the observations). I love how storm fire in SC KS by 21Z! Further west is much, MUCH better. In addition, it seems that all the vort is compacted into one lobe, which is progged to be perfectly timed with daytime heating. Also, sfc winds are still sig. backed, which is maximizing 0-1 km helicity and keeping storm motions down a tad. I love it! Now, if it'll just verify...