7/11/06 DISC: OH

Details regarding the exact extent of the damage are still varying, but several homes have lost large portions of their roofs in the southwestern Ohio area. I looked at the 00z sounding from Wilmington OH, which was VERY close to the area in question, and it definitely supports a tornado potential; SBCAPE around 1500 J/Kg, 0-1km SRH >200 m2/s2, T/Td of 77/72, and a resulting LCL of 300m. Pictures from various news sites show what appears to be an extremely large tornado moving through a forested area behind a neighborhood, though thankfully no injuries have been reported. The tornadic thunderstorms have since dissipated, but new convection has devoloped behind them in the past hour, which should remain below severe limits. I can't help but note that the SPC omitted the region from any type of risk (or mention) of severe thunderstorms.



 
I was chasing today and was in Cincinnati one hour before the tornadic storm developed, on my way from Indy heading south to get in front of the squall line in Louisville. Visually everything was junk and I could not believe the tornado warnings when they showed up on WxWorx. Synoptically, parameters seemed just to be not there. The cell was tiny on radar and did not have any ThreatNet meso markers that I saw. But that video at those links says it all. I thought something had to be up because those three adjacent counties were warned for a long time.

I believe this storm went up on a fresh outflow boundary from an earlier squall line that collapsed in southern Indiana. I saw several small cells try to go up along such a line that at least appeared that way.

The way things looked out there I'm very surprised that anything came of these cells. Everything south of I-70 was having a hard time keeping lightning going let alone much else. It looked like there was no upper support except in the far north.
 
Interesting video... I wish the houses weren't in the way so we could see ground contact. It's tough to figure out what that feature is, but I have to think that it's a a tornado given the proximity of the condensation to the ground and the obvious rotation. The motion of the condensation areas isn't anything impressive from a tornado standpoint, so I can't imagine winds were too intense at the surface. Personally, it's difficult to judge distance in that video, so I can't really say too much more. I was taken back by the calm and collected nature of the folks in the video. I'm tired of the screaming that tends to accompany many 'general public' videos.
 
Yeah, I noticed those cells too on the NWS website radar. They were definitely unimpressive to say the least, I figured it was someone who reported a scud...
 
Yeah, interesting video... It's quite likely a tornado (from what I could distinguish, the video showed substantial rotation and condensation more than 80% to the sfc). A few of the pictures I have seen of the tornadoes do appear to have condensation all the way to the ground (with one photo showing a large, fully condensated cone picking up lots of dirt). Its hard to tell if there was ground circulation based off the video, given the houses and trees blocking the view (given this was in poor chase country -- near and east of I-75 in southwest OH). It does appear that the main storm that produced these tornadoes was supercellular in nature (judging by a few radar grabs I've seen and a relatively pronounced RFD cut in several pics).

Meteorologically-speaking, while these tornadic events weren't from a "synoptically-evident" setup, reviewing the archived NAM and RUC forecast soundings across the region did indicate the potential for low-level mesocyclones. The 12z NAM forecasted considerable hodograph curvature (with strong 0-1km and 0-3km SRH) and substantial 0-3km low-level CAPE indicating enhanced low-level accelerations available to an updraft. On the other hand, deep-layer shear was quite weak (given the poor ~15-20kts midlevel flow) for a supercell structure (yet strong enough for sustained multicells. Nonetheless, there was enough low-level shear and CAPE to yield an isolated tornado threat with any updraft that could recieve surface-based inflow; with the forecast soundings for the region (both the NAM and RUC, for that matter) exhibiting no CINH for surface-based and mixed-layer parcels, which allowed for low LFC heights (e.g. 500-800m) -- enhancing the potential for ambient vorticity to be stretched and tilted vertically; which would allow for low-level mesocyclone augmentation (and possibley tornadogenesis if vorticity is amplified to tornadic strength). It's also possible the main storm interacted with a pre-existing surface boundary (which would serve as a source of pre-existing vertical vorticity that an updraft could ingest). I haven't done any real analysis on yesterdays environment as of yet -- although I'd look to sometime soon.

I'm rather surprised that SPC did not outlook portions of southern OH (prior to the 01z SWODY1 convective outlook) given the adequate CAPE and low-level shear (at least blanketed the region in a 2% TOR and mentioning for a few severe storms) forecasted prior by both the NAM and RUC. I haven't viewed the models in quite some time; so I certainly did not anticipate this event coming... At any rate, this is certainly an interesting event to perform additional research on.
 
There was a lengthy thread about this storm at Eastern US Weather. This pic was posted there. It is from WCPO. I think it's nice and conclusive as to the nature of the storm.

05.jpg


Here is a link to that thread:
http://www.easternuswx.com/bb/index.php?showtopic=100849
 
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