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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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: 420 Comments: 127549
283. chessrascal
8:06 PM GMT on May 06, 2007
The storms are blowing up!
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282. chessrascal
8:05 PM GMT on May 06, 2007
lol
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281. Dyce
4:02 PM EDT on May 06, 2007
Wow that's the first time i've ever seen them put us (belle isle) on the map.
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280. RL3AO
2:58 PM CDT on May 06, 2007
It lasted 8 years and 1 day. Now how long until the next EF5/F5 tornado.
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279. DocBen
7:57 PM GMT on May 06, 2007
Lots of rumbling around Wichita right now. Looks like we might add flooding to the story.
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278. chessrascal
7:56 PM GMT on May 06, 2007
.
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277. Patrap
2:56 PM CDT on May 06, 2007
6
Member Since: July 3, 2005 Posts: 420 Comments: 127549
276. Patrap
2:54 PM CDT on May 06, 2007
823
WUUS52 KTBW 061946
SVRTBW
FLC119-062015-
/O.NEW.KTBW.SV.W.0028.070506T1946Z-070506T2015Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE TAMPA BAY AREA - RUSKIN FL
346 PM EDT SUN MAY 6 2007

THE NATIONAL WEATHER SERVICE IN RUSKIN HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
CENTRAL SUMTER COUNTY IN FLORIDA.

* UNTIL 415 PM EDT

* AT 346 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM...CAPABLE OF PRODUCING PENNY SIZE HAIL...6
MILES NORTHWEST OF BUSHNELL...MOVING SOUTH AT 20 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
BUSHNELL.
NOBLETON.

MOVE INSIDE A STURDY BUILDING. DAMAGING WIND...LARGE HAIL...
TORRENTIAL RAIN...AND DEADLY LIGHTNING ARE EXPECTED. STAY INSIDE AWAY
FROM WINDOWS UNTIL THE STORM HAS PASSED.

QUARTER SIZE HAIL IS LIKELY. MOVE INDOORS IMMEDIATELY.

PLEASE REPORT TORNADOES OR FUNNEL CLOUDS...WINDS OF 58 MPH OR
HIGHER...HAIL THE SIZE OF PENNIES OF LARGER...AND ANY WIND DAMAGE TO
YOUR NATIONAL WEATHER SERVICE IN RUSKIN BY CALLING 813-645-2323
Member Since: July 3, 2005 Posts: 420 Comments: 127549
275. seminolesfan
7:53 PM GMT on May 06, 2007
lurkin',lurkin',lurkin'
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274. Patrap
2:54 PM CDT on May 06, 2007
6
Member Since: July 3, 2005 Posts: 420 Comments: 127549
272. V26R
7:50 PM GMT on May 06, 2007
Gotta get back to work, Take Care JP Stay Safe
Mike
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270. V26R
7:46 PM GMT on May 06, 2007
Guess you're under one of those radar returns JP?
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268. V26R
7:45 PM GMT on May 06, 2007
SPC had a MSdiscussion about the FLA aea as well as a Watch out for most of the state
Radar showing some BIG Boomers with Hail moving southerly

Link
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266. Chicklit
7:41 PM GMT on May 06, 2007
Bring it on...I'm having a pre-season hurricane party.
Member Since: July 11, 2006 Posts: 14 Comments: 11174
265. V26R
7:40 PM GMT on May 06, 2007
Looks like Central and South Fla is going to be in the crosshairs really soon
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264. Chicklit
7:38 PM GMT on May 06, 2007
I know, I'll go try to walk my dog and it will start raining...
Member Since: July 11, 2006 Posts: 14 Comments: 11174
263. Chicklit
7:37 PM GMT on May 06, 2007
I got to think with that big orange blob just north of us we're going to get somethin...
Member Since: July 11, 2006 Posts: 14 Comments: 11174
260. Chicklit
7:28 PM GMT on May 06, 2007
Still the bridesmaid....Ho hum. We may have some interesting activity here this summer though if the prevailing winds stay from east to west as they are now.
Member Since: July 11, 2006 Posts: 14 Comments: 11174
258. Chicklit
7:26 PM GMT on May 06, 2007
Yeah, it looks like it stayed off-shore and west of our area as it passed through, unless there's more to come from the north.
Member Since: July 11, 2006 Posts: 14 Comments: 11174
257. Chicklit
7:24 PM GMT on May 06, 2007
I'm between Daytona and Edgewater, just west of Ponce Inlet. It's just sprinkling here. Wondering if the action is to the west of us.
Member Since: July 11, 2006 Posts: 14 Comments: 11174
253. RL3AO
2:20 PM CDT on May 06, 2007
Can we say this was the first F5 since 1999 since both scales are rated on damage?
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252. FTmyersZ
3:19 PM EDT on May 06, 2007
station 41001 - 150 NM East of Cape HATTERAS

Conditions at 41001 as of
(2:50 pm EDT)
1850 GMT on 05/06/2007:
Unit of Measure: Time Zone:
Click on the graph icon in the table below to see a time series plot of the last five days of that observation.

Wind Direction (WDIR): N ( 10 deg true )
Wind Speed (WSPD): 19.0 m/s
Wind Gust (GST): 25.0 m/s
Wave Height (WVHT): 2.8 m
Dominant Wave Period (DPD): 5 sec
Average Period (APD): 5.1 sec
Atmospheric Pressure (PRES): 1008.8 mb
Pressure Tendency (PTDY): -1.9 mb ( Falling )
Air Temperature (ATMP): 16.7 C
Water Temperature (WTMP): 20.3 C
Dew Point (DEWP): 13.8 C
Member Since: August 26, 2005 Posts: 0 Comments: 60
248. Chicklit
7:17 PM GMT on May 06, 2007
Seven miles east of Osteen is well south of here! Looks like we've missed it again. Darn!
Member Since: July 11, 2006 Posts: 14 Comments: 11174
245. cajunkid
7:15 PM GMT on May 06, 2007
STORMTOP where are you?
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243. Chicklit
7:08 PM GMT on May 06, 2007
I'm hitting the wine a little early today so should be in good shape to watch the weather out my picture window which conveniently faces NORTH. (No sense trying to paint the fence or mow the lawn...and I already got my tennis game in!) So it's guilt-free slacking for me today. The thunder is getting louder, the leaves on the trees are moving sporadically, and the sky is a slate grey color. I'm going to refill my glass of wine and sit on my front lawn bench...
Member Since: July 11, 2006 Posts: 14 Comments: 11174
242. cajunkid
7:12 PM GMT on May 06, 2007
by-by dry air t-minus Link
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239. HurricaneKing
3:09 PM EDT on May 06, 2007
I've been here for along time. I had to take a break for a while but I'm back.
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238. Dyce
3:07 PM EDT on May 06, 2007
90 degree high and a afternoon thunderstorm. Starting to feel like summer.
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236. cajunkid
7:08 PM GMT on May 06, 2007
winding up Link
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235. Chicklit
7:06 PM GMT on May 06, 2007
...Although I'm quite happy to ride my bicycle to the beach with the wind coming at me and at my back on the way home...Wondering if that on-shore breeze is a sign of El Nina.
Member Since: July 11, 2006 Posts: 14 Comments: 11174

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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.