REPORT: 05/01/10 – ARKANSAS
Posted on 02. May, 2010 by Jesse in Jesse's Chase Logs, Uncategorized
Note: I noticed when I reviewed the video today that the iris was open too wide, so it won’t be winning any academy awards for crisp quality, but the features of the storm are discernible on the time lapse.
I chased with Kevin Crawmer on Saturday, initially staging near Stuttgart, Arkansas, which was a community with good road options that was co-located near a fairly evident Theta-E moisture boundary on KLZK radar for most of the afternoon. When we saw initiation near the Louisiana border, we bolted south, crossing the Arkansas River at Pine Bluff and intercepting the TOR warned cell in the video just NW of Monticello in extreme western Arkansas County. We followed the cell NE for the next several hours, constantly trying to play catch up due to getting cut-off by the river again as we trekked ENE, though we eventually abandoned the chase near Memphis after 10:00 PM. Near the end of the video I have put the speed into slow motion to show what appears to be some sort of a finger (or funnel?) beneath the lowering, as the storm was TOR warned the entire time until it went through the Memphis area. Some storm chasers on the ham radio simplex frequency were reporting a tornado, though we saw nothing that could be confirmed as such. The most interesting feature found prior to nightfall was the obvious lowering with enhanced LL convergence that has been time lapsed.
First and foremost the SPC was certainly justified in their issuance of the high risk for Saturday. All of the parameters were converging on central and eastern Arkansas for a respectable severe weather outbreak for Saturday afternoon and evening, so I would argue that, since the risk did exist, the forecast risk level was justified. However, given the fact that a high risk was issued for a potential tornado outbreak featuring strong to violent, long-track tornadoes, some are certain to begin pointing fingers to somehow justify blowing their chase expenses on an opportunity that didn’t exactly materialize for most in the field on Saturday evening. Very strong deep layer shear in the lower levels, coupled with SBCAPE values AOA 2000 J/KG ahead of an advancing shortwave created an environment very favorable for the development of supercells.
So what went wrong? There’s already been some speculation as to what might have prevented a major tornado outbreak on Saturday. One possibly hypothesis is that when storms actually fired around 00z -01z, there were numerous (app. 19 to be exact) storms that developed in central and southern Arkansas and far northern Louisiana, so potentially a “catastrophic” initiation of too many storms over a concentrated area in a relatively short period of time disrupted an environment that was otherwise felicitous for tornadogenesis.
However, based on the 00z sounding at LZK, a small cap near the surface is evident, though that wouldn’t have necessarily impacted some of the cells, such as ours, which was in a primed environment well to the south of Little Rock. The sounding does indicated relatively weak surface flow (~15 kts), along with a lack of stolid directional shear above the lowest 1 km. However, even 15 kts of surface flow coupled with the other parameters that were in place would have been enough to sustain rotation at the lowest levels, though the absence of a stronger mesocyclone creating deep rotation within the storms would likely have precluded a substantive threat for stronger tornadoes. Finally, as noted by the subsequent image, there was no strong wave moving through the region.
Was any or all of this a factor? Maybe and maybe not. However, this once again serves as a reminder that while the atmosphere doesn’t always perform to our expectations, it can continually provide us with an impetus to learn more about synoptic and mesoscale features that make or break a given day.
Author: Jesse Risley, with contributions from Convective Addiction’s Ryan Wichman and Danny Neal.
100502 00z sounding - LZK
0-3 km lapse rates 23z May 1st
Note the absence of a strong wave
Note the numerous T-storms developing by 00:26z
