Tuesday May 13 Chase

Early morning thoughts -- I'm planning to chase in OK later today, most likely within an hour or two of central OK. My expectation is for isolated to scattered supercells to develop along/east of a cold front and intersecting dryline later this afternoon/early evening. The morning observed sounding from Norman exhibited a stout elevated mixed layer/cap, however sufficient boundary layer converge and surface heating should lead to at least isolated storm development later today. Experimental 4km WRF-NMM and 4km WRF-NSSL models both lead credence toward central OK initiation, with each model developing a supercell or two near the OKC metro by around 00z. Given the 71F dewpoint and 14.4 g/kg mean mixing ratio in the Dallas-Fort Worth 12z raob, it would appear there is a good shot at upper 60s F dewpoints into central OK. With the strong instability and good deep layer shear, the conditional potential for supercells is high -- it's just a matter of initiation, and the extent thereof. I'm not particularly high on well-sustained tornadoes given the initially modest low level flow, with weaknesses likely from the surface through 2-3 km per model soundings. However, there is certainly some tornado threat, along with the potential for very large hail.

May 7 Chase Summary

Being May 7th, I figured it was about time to get my first chase of the season in -- long overdue. Not really wanting to commit to north TX, I decided I would hang around within an hour or two of Norman in an attempt to find a rogue low topped supercell/tornado near the advancing surface low and adjacent surface boundaries (wind shift and sagging cold front). My initial target was the Duncan, OK area, largely driven by the position of the surface low along with model forecasts (and later objective analysis trends) of low level CAPE/lapse rates etc. I watched the back side of the initial Stephens County storm as it quickly developed and went severe. Since I was west of that storm, I decided to sit tight for a while and keep an eye on the upstream development across southwest OK/far north TX. But after taking in some data, and seeing the surface winds come around to westerly at Ardmore/Duncan (while still backed near the OKC metro), I decided to relocate northward for a play west of the OKC metro. I didn't exactly expect a tornado given the surface inhibition and lack of low level CAPE etc., but figured the vorticity-rich area near the surface low/boundary intersections was still worth a shot. I was coming through Mustang when the tornado warning for Oklahoma County was issued. I tried to weave my way north/eastward from there, but Hwy 152 and I-44/240 were largely bogged down with cars stopped for the tornado warning. Very low clouds/plentiful precipitation otherwise blocked my view of the storm that did damage on the northwest side of OKC.

May Day Supercell from Norman

Isolated to scattered supercells developed along the dryline yesterday (May 1) afternoon across central OK. In particular, a supercell began to develop just west of Norman by around 615 pm, moving northeastward and producing large hail (plenty of 1.5-1.75" reports, isolated up to 3") across the east part of the OKC metro by 7 pm, including the Midwest City area. Above is a picture of the backside of this supercell -- looking north/northwest from Norman just as it began producing some of the larger hail. A vigorous updraft and impressive backsheared anvil are evident in the middle to upper part of this supercell storm.

Thurs April 3 - No Go

A no-go for me... contrary to my optimism early yesterday, I ended up not chasing today. Had several concerns regarding the impact of the lead impulse/shortwave trough today and initially (pre-dark) modest low level SRH etc. within a couple hours drive. Only exception will be if something develops near here before sunset.

Spring 2008 - Thurs April 3 Chase Potential

Just a quick post to say that it looks like I'll be able to get my first chase of 2008 in on Thursday. A look at Tuesday evening model guidance/forecast soundings suggest a rather ominous scenario, with supercells likely especially across southern OK and north TX. I see no reason why there won't be at least some tornadoes. The good thing... short drive as it may be close to home... the bad thing, it's potentially close to home!? At 36+ hours out, my prelim target is Duncan, OK (south central OK). Anyways, I do look forward to getting out in the field for the first time this year.... I'll have to dust off the gear tomorrow. More later.

Erin Remnants

Woke up early this morning to see that "Tropical Storm" (for all intensive purposes) Erin has apparently undergone some intensification/increased organization across west central OK overnight, with very heavy rain/flooding and strong wind gusts problematic. In the attached image, one can clearly the remnant eye of Erin -- Wow! -- just west of the OKC metro in Canadian County -- OKC and Norman are roughly in the center of the image. A quick perusal of some obs early this morning shows we've had 4+ inches of rainfall overnight in Norman, with more to come this morning. We've had 40 mph measured gusts overnight in Norman. Farther west, there's been a number of measured 60-80 mph gusts and reports of wind damage since late last evening closer to the center of circulation, along with considerably higher rainfall amounts (see second image).

Night Shots from Norman MCS

As of this late night post, an apparent derecho continues to plunge southward across north TX with high winds ongoing. This MCS produced at least 40-50 mph winds as it moved through Norman soon after midnight. Unfortunately, cloud-to-ground lightning didn't really cooperate for me as I viewed the incoming storm from west Norman, but below are a few pictures of the approaching shelf cloud/gust front around midnight.