Monday, March 8, 2010

First WTF?!? day of the season

So as most weather nerds know already there was a long track tornado in western Oklahoma today. Andy Gabrielson of Luverne, MN who I have chased with a few times caught some great footage of the tornado near Hammon, OK in the later afternoon. Bart Comstock also got some great video and both have some of their footage playing on TWC so congrats to both on bagging the tornado and getting the footage on several news outlets. This was a day that noone really expected, and the chasers that did go for it were pretty skeptical. Temps barely breaking 60, dewpoints barely breaking 50, and models showing far less than par helicities over the area that had the tornado. For some chasers and wx nerds here in Minnesota and Wisconsin this might sound somewhat familiar. August 19th, 2009 had SOMEWHAT of a same setup. Relatively cool temps and low instability. While there were many differences between 8/19/09 and today, cool core nature and low instability dynamics are obviously major factors. MLCAPE values were ~500-750 j/kg (8/19 here in MN MLCAPE were around 200-300). The forecast models were showing the helicity today being pretty low, definitely not what you would expect for a long track tornado. The forecasted helicities for 8/19 in MN were pretty big. While I can't be 100% sure about this since I am no expert but I'm guessing that for today the models were neglecting to pick up on on the localized shear just to the east/northeast of the center of the low which is where the tornado touched down. I don't know how strong this low was since I wasn't really paying attention, but regardless the shear will be maximized in the area mentioned above. Couple strong shear (eventhough no one knew it was there) with just enough instability and you get what we had today. There was someone at ST who said they drove though 1.5" hail in the core of the storm so it's possible a brief tornado would've touched down with even less instability, but nothing like what actually happened. Another amazing thing is how good the visibility was today given that it was a cold core event. Days like today are the reason we chasers go out on days that don't look good because every once in a while it will really pay off. Also just goes to prove that there doesn't need to be a tornado watch or even warning (severe t-storm warning for that matter) before you get a tornado. It is also very important to note that this storm did not look good at all on any level or any scan. There was no way to know what it was about to do because it was so far away from any radar site and at that distance you can't see the lower levels of the storm. It had no couplet on velocity, no hook, no organization all on radar, and tops only ~30k ft. Nothing about this setup looked good except the storm itself, which is ultimately the most important thing. I think it was great listening to TWC and listening to them talk about how big of a role Spotter Network played in getting the warning out. I'll definitely have to keep these kinds of days in mind for the future. Congrats again to Andy, Bart, and everyone else who got the tor today!


Timothy said...

The low was somewhere in the mid 990's mb range the day of the tornado, and I agree about the great coverage on TWC! Looks like Today could be quite active in Arkansas and nearby states.

Midwestchaser said...

Wow, 990 that's pretty good! Didn't realize it was that strong. Wish I would've caught TWC when they were showing Bart's stream of the tornado live. But I was able to catch the tornado live on his stream at SevereStudios. Pretty cool, I've never done that before.