Another wild night in Tornado Alley

By: Dr. Jeff Masters , 11:40 AM GMT on May 06, 2007

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The sirens sounded two more times in tornado-ravaged Greensburg, Kansas last night, as two more twisters tore through the county. However, both tornadoes missed populated areas, as did most of the approximately 75 tornadoes that touched down yesterday. The action should quiet down considerably today; the Storm Prediction Center (SPC) has placed most of Kansas and Nebraska under its "Slight Risk" area for severe weather. Sweetwater, Oklahoma received significant damage from a tornado last night, and we've saved 300 Kb animations of the radar reflectivity and Doppler velocities of the tornado.

It will take a long time for Greensburg to recover from Friday's tornado. To get an idea of the scale of devastation, see the aerial photos posted by the Wichita Eagle. Damage surveys are not yet complete on the tornado, but photos I've seen of the destruction show damage consistent with EF4 winds(168-199 mph). It is possible the storm was an EF5 (winds more than 200 mph). The nine deaths from the tornado bring the U.S. tornado death toll to 68 so far this year, two more than the toll for all of last year.

We've saved some extraordinary 1 Mb animations of the radar reflectivity and Doppler velocities of the tornado. I asked wunderground meteorologist and tornado expert Rob Carver to comment on what's going on in the animations, and here was his analysis:

This was likely an example of cyclic mesocyclogenesis. In a nutshell, the rear-flank downdraft surges out, wraps around and occludes the mesocyclone (Meso A for short). Meso A then veers to the left and dies, this is why tornado family members curve to the left as they dissipate. While Meso A is dying, a new meso spins up and becomes the dominant meso. Now, while I've seen plenty of simulated cyclic cases where the hook retreats when Meso A occludes, I don't think I've seen anything as dramatic.



Figure 1. Radar image of the storm that spawned the Greensburg, KS tornado of May 4, 2007, showing the clearly defined hook echo associated with the twister.

Coastal Carolina storm
The latest (8pm EDT) computer forecast models continue to show a moderately strong coastal storm developing several hundred miles southeast of Cape Hatteras, North Carolina, on Monday. The storm will be extratropical in nature when it forms. We'll have a lot of time to watch the storm, as it is expected to meander offshore for five days and gradually weaken. Water temperatures are 22-23 C off of the coast, which may be warm enough to allow the low to acquire some subtropical characteristics and become the season's first named storm. The models are hinting that the storm could remain over water long enough for this to happen, and I put the odds of a Subtropical Storm Andrea forming late this week at about 20%.

Wunderblogger Mike Theiss was out chasing yesterday and caught some of the storms; be sure to tune into his blog over the next few days to read his chase accounts. Stormchaser Dan Robinson posted some video stills of the Greensburg tornado.

Jeff Masters

()
Storm Brewing (thomasanthony)
A big storm moved in on the 3rd. Wasn't as bad as it looked though.
Storm Brewing

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334. sporteguy03
8:57 PM GMT on May 06, 2007
JP,
6000 Lightning Strikes in Central FL since 12 noon!
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333. Thundercloud01221991
8:57 PM GMT on May 06, 2007
http://www.ndbc.noaa.gov/quikscat.php?station=41001

Definetly some ciculation
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332. weathersp
4:49 PM EDT on May 06, 2007
I found something Scary when searching around the Internet for the actual report of the Greensburg Tornado.


Click on the image to see it closer up
The full size and power of the greensburg tornado
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330. Drakoen
8:53 PM GMT on May 06, 2007
Posted By: HurricaneFCast at 8:52 PM GMT on May 06, 2007.

Wow, possibility of tropical cyclogenesis just increased. Thanks Michael, I didn't realize that the front was already warm-core.. Ehhh, not good. Michael, do you have a link to Current SST's for the Atlantic Basin, and maybe cropped down to the GOM & Southeast coast? That would be awesome. I'm looking at the Wind Shear forecast for the next 2-5 days and it seems like that will be a factor, wind shear does appear to be dropping, if it continues to do so and remains under 10-15 knots, we could see tropical cyclogenesis.

yea things are getting very exciting now. Golf Stream Temperatures at 80 degrees and winds at 36 miles sustained. The cyclogenisis is improving. You can see on the satellite imagery that it has the wrapping feature already. Although ont much convection associated with it as far as thunderstorm activity that could change in a few hours.
Member Since: October 28, 2006 Posts: 57 Comments: 29938
326. sporteguy03
8:51 PM GMT on May 06, 2007
JP,
Is the system in question just off the Carolina Coast or FL Coast?
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325. chessrascal
8:51 PM GMT on May 06, 2007
yeah it probably was. Adrian has it mines a trial i just didnt want to bother to pull up Storm Predator
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324. savedbygod
8:45 PM GMT on May 06, 2007
MSTL...There is a weak system in the Gulf now. If they meet as it looks like they would, if the one in Florida moved to the Gulf; would that give it a stronger chance of strenthening?
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323. HurricaneFCast
8:45 PM GMT on May 06, 2007
Wow, possibility of tropical cyclogenesis just increased. Thanks Michael, I didn't realize that the front was already warm-core.. Ehhh, not good. Michael, do you have a link to Current SST's for the Atlantic Basin, and maybe cropped down to the GOM & Southeast coast? That would be awesome. I'm looking at the Wind Shear forecast for the next 2-5 days and it seems like that will be a factor, wind shear does appear to be dropping, if it continues to do so and remains under 10-15 knots, we could see tropical cyclogenesis.
Member Since: April 20, 2007 Posts: 7 Comments: 1482
319. Drakoen
8:48 PM GMT on May 06, 2007
Yes thundercloud, but at the time there is very little thunderstorm activity associated with it even though the winds speeds are tropical depression strength. There is clearly a low though and you can see it sorta "wrapping" the rain clouds around it.
Member Since: October 28, 2006 Posts: 57 Comments: 29938
318. chessrascal
8:47 PM GMT on May 06, 2007
Posted By: StormW at 8:39 PM GMT on May 06, 2007.
Posted By: chessrascal at 8:38 PM GMT on May 06, 2007.



view from my radar software.

chessrascal, what software is that?


ITS GRlevel3
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317. RL3AO
3:47 PM CDT on May 06, 2007
it will need to get alot more compact if it wants anychance at being named. I'm wondering if the NHC will even name it if its sub-tropical just to aviod the media crap of a named storm in May.
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315. Thundercloud01221991
8:44 PM GMT on May 06, 2007


Look to the right you can clearly see the circulation and the increasing convection
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314. Drakoen
8:45 PM GMT on May 06, 2007
Posted By: MichaelSTL at 8:44 PM GMT on May 06, 2007.

The CMC and NAM are still forecasting a tropical storm; in fact, it is already warm-core but frontal:


yes. Just where will it go though. That high is the determining factor.
Member Since: October 28, 2006 Posts: 57 Comments: 29938
312. Thundercloud01221991
8:43 PM GMT on May 06, 2007
at 44001 the winds already are tropical storm strength.
Thanks I forgot to convert from knts
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311. Bamatracker
8:44 PM GMT on May 06, 2007
any chance the low will cross florida and get into the gulf of mexico?
Member Since: May 17, 2006 Posts: 6 Comments: 1367
310. savedbygod
8:34 PM GMT on May 06, 2007
I'm adding you Floridians to my prayers. I pray for the rain that you desperately need, without the severity of the storms ripping through our portion of tornado alley. It came a little closer to us today. Had our babies (cats & dogs), ready to hit my son's basement next door. Looks as if the night will be long for all of us. Good Luck
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309. Drakoen
8:41 PM GMT on May 06, 2007
I really hope that low comes into florida as we need the rain badly especially in south flroida all we can do is hope. Right now its just a coastal low if that.
Member Since: October 28, 2006 Posts: 57 Comments: 29938
307. Thundercloud01221991
8:41 PM GMT on May 06, 2007
Winds are approaching Tropical Storm Strength
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304. chessrascal
8:37 PM GMT on May 06, 2007
radar

view from my radar software.
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302. sporteguy03
8:33 PM GMT on May 06, 2007
Jp we are getting strong winds here near Disney..strongest I've seen since 04
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301. sporteguy03
8:29 PM GMT on May 06, 2007
Michael,
What does that mean if it moved over land?
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300. RL3AO
3:30 PM CDT on May 06, 2007
Once the front gets out of here we will be able to see the system clearer.
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299. Drakoen
8:29 PM GMT on May 06, 2007
Its still fairly disorganized and not much heavy thunderstorm activity located with it.
Member Since: October 28, 2006 Posts: 57 Comments: 29938
298. chessrascal
8:28 PM GMT on May 06, 2007
sorry i cant post the link computer trouble: http://www.wunderground.com/radar/radblast.asp?ID=TBW&lat=0&lon=0&label=you&type=N0R&zoommode=pan&ma p.x=400&map.y=240¢erx=400¢ery=240&prevzoom=zoom&num=1&delay=15&scale=1&noclutter=1&showstorm s=31&showlabels=1&rainsnow=1&lightning=1
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295. sporteguy03
8:25 PM GMT on May 06, 2007
Jp very smokey air in clermont, very windy too, I thought fronts don't come this far south?
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293. chessrascal
8:22 PM GMT on May 06, 2007
lol

a closeup
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290. Drakoen
8:22 PM GMT on May 06, 2007
Ah so this is the system. Taking shape!
link
Member Since: October 28, 2006 Posts: 57 Comments: 29938
289. chessrascal
8:21 PM GMT on May 06, 2007
that is one wide twister. Thanks for posting the article Michael.
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288. sporteguy03
8:20 PM GMT on May 06, 2007
Does Bruce Edwards still work at the Weather Channel?
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287. Chicklit
8:17 PM GMT on May 06, 2007
While walking' the dog, heard the sound and the fury...signifying nothing (at least for east central fla...) It's south of here.
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286. sporteguy03
8:09 PM GMT on May 06, 2007
JpHurricane,
Windy tomorrow why?
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284. Patrap
3:09 PM CDT on May 06, 2007

472
WFUS54 KOUN 062007
TOROUN
OKC151-062030-
/O.NEW.KOUN.TO.W.0042.070506T2006Z-070506T2030Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE NORMAN OK
306 PM CDT SUN MAY 6 2007

THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A

* TORNADO WARNING FOR...
WOODS COUNTY IN NORTHWEST OKLAHOMA...

* UNTIL 330 PM CDT

* AT 306 PM CDT...A DEVELOPING TORNADO WAS DETECTED BY DOPPLER RADAR
7 MILES SOUTHWEST OF FREEDOM...MOVING NORTHEAST AT 35 MPH.

* THE TORNADO WILL BE NEAR...
FREEDOM AROUND 315 PM CDT...
CAMP HOUSTON AROUND 320 PM CDT...

IN ADDITION TO A TORNADO THREAT... THIS STORM LIKELY CONTAINS
DAMAGING HAIL TO THE SIZE OF BASEBALLS OR LARGER.

TAKE COVER NOW. LEAVE MOBILE HOMES AND VEHICLES. IF POSSIBLE...MOVE
TO A BASEMENT OR STORM SHELTER. OTHERWISE MOVE TO AN INTERIOR ROOM OR
HALLWAY ON THE LOWEST FLOOR. STAY AWAY FROM WINDOWS AND OUTSIDE
WALLS.

LAT...LON 3681 9926 3679 9917 3668 9903 3692 9892
Member Since: July 3, 2005 Posts: 421 Comments: 127664

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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