Killer Tornado in Evansville, Indiana

[Mike Johnston]

Ah, Jeff, now I get it even more. I was making an incorrect assumption the LLJ was primarily a feeder of warm, moist air (probably because - whenever I think 850mb, I'm on the lookout for warm air advection.) Your explanation makes it more clear that the nocturnal LLJ is more a source of enhanced sheer than a feeder for surface instability. It also made me remember the LLJ can "slide" more easily once the boundary layer is de-coupled, which is something I knew but forgot. I guess, in hindsight, this was just a situation where strong kinematics won out.

The cell that prompted the tornado warnings was quite prominent and bulged out over the squall line, reflecting higher dbz and VIL signatures. Wish I would have screen-saved some of those last night; I was so amazed at what I was seeing (and so p***'d off TWC wasn't picking up on it at all), I didn't even think about it. Anyway, thanks for the explanations.

 

[Jeff Snyder]

Originally posted by Mike Johnston
Ah, Jeff, now I get it even more. I was making an incorrect assumption the LLJ was primarily a feeder of warm, moist air (probably because - whenever I think 850mb, I'm on the lookout for warm air advection.) Your explanation makes it more clear that the nocturnal LLJ is more a source of enhanced sheer than a feeder for surface instability.

It is a "feeder of warm, moist air", but not so much at the surface (the LLJ is primarily used to describe the jet in the 900-750mb range). Since the LLJ is above the surface, the warm, moist air that "rides" the LLJ affects (or defines) the low-level warm-air advection regime. In other words, as the boundary layer decouples, the increased WAA caused by the increased LLJ doesn't really affect the surface layer -- so surface-based instability is not really affected (and usually decreases rapidly as the surface layer cools). Oftentimes, the strengthening LLJ does help drive elevated convection, as strong isentropic lift develops and lifts elevated parcels to their LFC.

 

[Kevin Bowman]

Originally posted by rdale
\"SEVERE THUNDERSTORMS CAN AND OCCASIONALLY DO PRODUCE TORNADOES.\"

I tire of people saying that the public needs to be alert for an F3 tornado in a SVR warning... Remember, SVR warnings are supposed to mean \"you could be hurt or killed.\" Do they? Nope. Will they in the future? Probably not. So since we all know that a SVR means \"this is a bad storm, but likely won't do you any harm\" we can't use that as an excuse for residents not taking cover.

In this case, nobody expected a major tornado to form near EVV. Nobody.

no one expected the plainfield F5 either since it was under a svr watch and warning at the time

 

[Angie Norris]

Andrew, the "tornado report" came from MSNBC this morning...they were saying damage from a "possible tornado" in TN. There were 8 LSRs from west and middle TN, but they were all wind damage. Nothing confirmed that I know of.
Angie

 

[rdale]

"no one expected the plainfield F5 either since it was under a svr watch and warning at the time"

That's a little different... Plenty of people (FAA / public service employees / spotters) knew about the Plainfield F5 - it's just that nobody bothered to tell the NWS.

What I'm saying is you can't pull the "SVR's CAN PRODUCE TORNADOES" line and equate that to "THEY SHOULD HAVE BEEN WATCHING."

- Rob

 

[Michael Auker]

Sounds like the special investigative team will have to make a determination of the strength of the tornado. Paducah calls it a F-3, but says it might be stronger. Tim Marshall is on that team, isn't he?

 

[Glen Romine]

Originally posted by Jeff Snyder
The upper-level dynamics were strong, but there was very little in the way of surface-based instability. Typically, as the sun sets and the surface layer cools, substantial CINH develops, which is largely the reason why we typically see a transitition to elevated convection overnight. The strong surface low created a strong pressure gradient and resultant strong gradient wind. This likely kept the boundary layer semi-well mixed, prohibiting decoupling and a transition to a parcel updraft above the surface ('elevated convection').

Of course it's tough to know how much instability was really present since there were no representative soundings, but if you modify the ILN sounding at 12Z for the sfc conditions at EVV and assume it is roughly representative - it's probably ~1000 J/Kg. Also, I agree the strong LLJ likely prevented decoupling through strong mechanical mixing, coupled with weak warm advection. Note the EVV sfc temp was nearly constant at 71 from 2pm to 1 am prior to the arrival of the storms.

Glen

 

[Tyler Allison]

If anybody cares I have the raw Level 3 data from KVWX available in NCDC format on AllisonHouse for free download.

Time window is 0600 to 0800 GMT

http://nexrad.allisonhouse.com/downloads/K...051106-L3.tar.Z

I'll leave it up for a few weeks to give the NCDC time to update their archives.

If anybody wants a different radar site drop me an email or PM and I'll package it up. But let me know within a day or two or my auto-purger will take over.

 

[Glen Romine]

Originally posted by Tyler Allison


Time window is 0600 to 0800 GMT

Thanks for posting these.

The view from there looks pretty good - but could you grab the times through about 0830Z? Tornado is still ongoing in the last frame it appears.

Glen

 

[Tyler Allison]

package updated to include time through 1000 GMT

 

[nickgrillo]

Originally posted by Tyler Allison
If anybody cares I have the raw Level 3 data from KVWX available in NCDC format on AllisonHouse for free download.

Time window is 0600 to 0800 GMT

http://nexrad.allisonhouse.com/downloads/K...051106-L3.tar.Z

I'll leave it up for a few weeks to give the NCDC time to update their archives.

If anybody wants a different radar site drop me an email or PM and I'll package it up. But let me know within a day or two or my auto-purger will take over.

If you could, could you unTAR a few of the files for me? I'd only need a few... I would like them in a reguler format (GIF, PNG, etc.).

 

[Scott Olson]

Here are a couple screenshots from the data.

BR4 6.000-8,000 feet a couple minutes prior to the trailer park being hit.


Right before Trailer park gets hit. Red Dot is a rough guess of Trailer Park.

 

[Bill Schintler]

Case study for this morning's storms

I’m Just now looking over the data for this event that took place earlier today. Since I didn't look at/nor archive data from the event as it unfolded, I'm now reviewing a number of 12Z SFC and UA charts (3 hours after the deadly tornado in Evansville, IN), in addition to hourly surface data from the region. Also, I haven't yet read every post on this thread, so I apologize if I'm repeating something that has already been mentioned.

Overall, it looks as though this event was characterized by marginal instability coupled with very impressive shear, forcing, and dynamics. This is not at all unusual for this time of year. Looking at the 250mb upper-level chart, especially noteworthy is the exit region of a 90kt jet max and somewhat of a coupled jet structure resulting in impressive divergence and upward forcing over Ohio. During the time of the storms, this upper-air environment would have been 150-200mi or so upstream (to the west) over southern IN/northern KY. Attendant very strong mid-level flow with a potent streak (85kt at 500mb, and 75kt at 700mb) is also noted. This streak, coupled with SSW surface winds of around 15mph, would have resulted in deep-layer (0-6km) shear values of 70 kts or more. Additionally, hodographs were very long and somewhat curved below 800mb. See the Wilmington, OH hodograph for 12Z, which shows this well. This sounding/hodograph also indicates a 0-3km SRH of 876 m^2/s^2!

So, one can see that these impressive dynamics and shear have overcome rather marginal instability (Evansville T/Td = 69/62 at 2 AM, contributing to SBCAPE’s of on the order of 1000J/kG).

- bill

 

[Brett Adair]

Originally posted by Tyler Allison
package updated to include time through 1000 GMT

For some reason, I can't get the TAR file to unpack through my .rv3 converter. Is there an error in the file, Tyler?

 

[B Doss]

F3 gets my vote. Spoke with my sister who lives near the state line between Henderson and Evansville. It came close but she didn't sustain any major damage, tornadic or otherwise.