05.10.10

Chase #5

Posted in Severe Weather Forecast, Storm Chasing at 9:22 am by Rebekah

SPC Day 1 Convective Outlook

Hmm…where to start.  The first High Risk on the Southern Plains since April 26th of last year, and the third High Risk in less than two weeks.  The SPC has the tornado risk at 30% hatched, meaning there’s the potential for EF2 or greater tornadoes within 25 miles of a point.

A shortwave trough is fast approaching and is expected to be over central Kansas / northern Oklahoma by evening.  A surface low will move across southern Kansas today, as a warm front lifts through Oklahoma up into central Kansas.  A dryline will tighten over west central Oklahoma by late afternoon/evening (NAM dryline keeps pushing back west…something to keep an eye on…), when a narrow band of 70F dewpoints is forecast to stretch north through central up into northeastern Oklahoma.

CAPE of 3000 to 4000 J/kg is expected along the dryline, from northeastern Oklahoma southward all the way to San Antonio.  Mid-level lapse rates will be very steep in this region, approaching dry adiabatic.

With south-southeasterly surface winds in central into eastern Oklahoma and southeastern Kansas (the NAM shows better backed southeasterly winds in north central/northeastern Oklahoma and southeastern Kansas, ahead of a dryline a bit farther west of the GFS), and west-southwesterly winds at 500mb, shear profiles will be more than sufficient for rotating storms.  The NAM shows 0-1 km storm-relative helicity values of over 100 in most of Oklahoma (ahead of the dryline), with over 400 in northeastern Oklahoma into eastern Kansas and Missouri (0-3 km SRH is over 300 in Oklahoma and over 500 in northeastern Oklahoma into eastern Kansas and Missouri).  Soundings and especially hodographs appear to be textbook for classic supercells in much of Oklahoma (from I-35 east) and southeastern Kansas.

Everything appears to be coming together for a major severe weather outbreak from central into northeastern Oklahoma and southeastern Kansas (although severe storms are certainly possible all the way south along the dryline into west central Texas).  Without much of a cap (GFS shows a stronger cap, but it shouldn’t be much of a problem–if anything, it could help stronger, more isolated storms to form), it looks as if there will be supercells with large hail and strong tornadoes from central Oklahoma into southeastern Kansas (and possibly southwestern Missouri near/after dark).

A few early showers in northeastern Oklahoma and south central to southeastern Kansas could set up a few outflow boundaries to assist in storm development later in the day.

Storm motion could be a problem as far as chasing goes, today, as the storms will be moving fast (near 40 mph) through an area with some trees and not the best road network.

Nevertheless, I will be out there streaming today (see my tracking page on my web site), somewhere in north central to northeast Oklahoma.  VORTEX2 is already up in the area, hoping to finally record some quality data, hopefully in rural areas.

My target area for the last couple of days has been Ponca City, Oklahoma to Arkansas City, Kansas.  If the NAM comes closer to verifying on the dryline than the GFS, storms may form farther west in north central Oklahoma / south central Kansas…however, as storm motions will be pretty fast, it would be better to stay ahead of where I think the storms will form, so I don’t have to play catch-up as much.

I think for now, I will target Blackwell, Oklahoma.  I’ll discuss with my chase partners, Jeff and Esther, within the next hour, to see what they think, and then we’ll probably head out around 10:30 to 11 AM…

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