Dr. Jeff Masters' WunderBlog

Greensburg tornado an EF-5; coastal storm will bring 3-5' storm surge to Carolinas

Posted by: Dr. Jeff Masters, 14:42 GMT le 07 mai 2007

The huge, 1.4 mile-wide tornado that devastated Greensburg, KS on Friday night, May 4, was an EF-5 tornado on the Enhanced Fujita Scale. A preliminary damage survey by the National Weather Service found that the storm likely had 205 mph winds, putting it just above the 200 mph wind threshold for an EF5 rating. This is the first tornado ever rated as an EF5 using the new scale, adopted in February of 2007, and the first tornado to receive a "5" rating since the May 3, 1999 Moore-Bridge Creek tornado that devastated the southern suburbs of Oklahoma City. Had the Greensburg tornado hit downtown Chicago, the death toll could have easily been in the thousands, as I discussed last month in my blog, "Big Wind in the Windy City".

The severe storm action finally quieted down yesterday in Kansas and the Plains; only 11 reports of tornadoes were received, compared to 93 on Saturday and 33 on Friday. The severe weather action should stay at a slow simmer through Wednesday over the Plains; the Storm Prediction Center (SPC) has portions of the region under its "Slight Risk" area for severe weather through Wednesday. Flooding is a major concern now; most of eastern Kansas, plus large portions of Oklahoma, Texas, Missouri, Iowa, Nebraska, and South Dakota are under flood warnings. More heavy thunderstorm rains during the week are expected to add to the problem.

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.

Wunderblogger Mike Theiss was out chasing the weekend storms; be sure to tune into his blog over the next few days to read his chase accounts.

Figure 1. Visible satellite image of the May 7, 2007 coastal storm.

Coastal Carolina storm
A powerful non-tropical low pressure system formed off the coast of North Carolina last night, and is bringing tropical storm-force winds as high as 55 mph to the waters offshore the Carolina coast, according to the latest QuikSCAT satellite wind estimates. The North Carolina Diamond Shoals buoy had 17 foot seas and sustained winds of 43 mph at 9am EDT this morning, and buoy 41001 about 175 miles east of Cape Hatteras recorded sustained winds of 62 mph gusting to 80 mph at 1am this morning. Seas were 41 feet at this buoy this morning! The strong winds will bring 10-20 foot seas and significant beach erosion to the shores of North Carolina, South Carolina, and northeast Florida through Wednesday. A 3-5 foot storm surge is expected along portions of the North Carolina coast through Tuesday morning. The latest set of computer model runs have the storm drifting slowly southwest, and bring it ashore between the South Carolina and northern Florida coast on Wednesday. The storm will start to develop thunderstorm activity and a warm core, but will probably not have time to become fully subtropical and become Subtropical Storm Andrea. However, the storm is only expected to weaken slowly, and will have an impact similar to a tropical storm in regards to offshore winds and coastal flooding today and Tuesday. If the storm does indeed make landfall on Wednesday as expected, it will most likely be of tropical depression strength, with top sustained winds around 30-35 mph. Heavy rains of 1-3 inches can be expected to the north of where the center makes landfall, but rains will not be as significant as what a tropical storm would bring.

I'll have an update on this storm Tuesday morning.
Jeff Masters

Raging Waters - Mill Creek1 (Cptkirk)

Same location - evenig shots!

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Storm Cloud Formation (FT2)

Detail of Turbulance Under the Trough on 05/06/2007 in SE Iowa.

Categories: Tornado

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1001. Jedkins 14:39 GMT le 08 mai 2007
Levi is right on target folks, I have been a little harsh I admit, but please understand what I have stated, and I rest my case from here.

1002. Chocolatethunder 14:40 GMT le 08 mai 2007
Link Al just makes me laugh........I love the weather

1003. Jedkins 14:41 GMT le 08 mai 2007
Hey look at last few sattelite frames, looks like its headed for Florida, it might just be a job, but its worth watching further.

1004. Levi32 14:41 GMT le 08 mai 2007
This blog is already going down the slippery slope that it was last year.... No one wants to listen to anyone else. And now the arguing sets in. Gee wiz guys. Pull it together. Do you really think anyone is going to want to read this to get info when major hurricanes are making landfall in August?? Member Since: 24 novembre 2005 Posts: 586 Comments: 25459

1005. Jedkins 14:41 GMT le 08 mai 2007
jog*

1006. SCwxwatch 14:41 GMT le 08 mai 2007
Jedkins this is a blog! The only person being childlike is you! A blog is meant for conversation, nowhere in the introduction of this blog does it remotley mention this is a Professional or experts blog. Get your head out of your arse and quit acting like your some sort of professional , because we can all see through your idiotic antics. We are all here for discusion you seem to be the only one who wants to argue. Now be gone Troll!!

1007. rxse7en 14:42 GMT le 08 mai 2007
LOL! @ GulfScotsman. Love it when the easily-angered get tormented...or is that a real prediction? :D B Member Since: 21 août 2005 Posts: 0 Comments: 526

1008. kmanislander 14:43 GMT le 08 mai 2007
90L is now up on the Navy site. Don't know if anyone has posted this yet so apologies if you all know this Member Since: 19 août 2006 Posts: 0 Comments: 14939

1009. thelmores 14:43 GMT le 08 mai 2007
"CAT 1 landfall near Savannah." no fair! I called Savannah yesterday! LOL Member Since: 8 septembre 2005 Posts: 0 Comments: 3748

1010. Patrap 14:43 GMT le 08 mai 2007
u2 Member Since: 3 juillet 2005 Posts: 372 Comments: 111617

1012. thelmores 14:44 GMT le 08 mai 2007
Kman..... you'd have a tough time getting "anything" by this crowd! LOL Member Since: 8 septembre 2005 Posts: 0 Comments: 3748

1013. Chocolatethunder 14:46 GMT le 08 mai 2007
Is it me or are we starting to see a prelude to an active season of tropical weather?

1014. ForecasterColby 14:46 GMT le 08 mai 2007
No hard feelings, agreed. I'm off for an AP exam, will be back later. /cheer for Andrea!

1015. incogNeato 14:46 GMT le 08 mai 2007
The arguing about the status of the storm is pretty humorous... it defines the world of subtropical storms! How "subtropical" does it need to be to be called "subtropical". I don't think there's a soul on here who could possibly argue that it is either 100% tropical or 100% extratropical. The question is, how much is enough to call it subtropical? Very subjective, IMO. Given its virtually complete frontal disconnect this morning, I'd say it crosses the threshold for my opinion. But with the disorganization of the convection and lack of much near the center... I can certainly see the opposing opinion - the one to which NHC is apparently subscribing. Subtropical storms are such a joy.

1016. thelmores 14:49 GMT le 08 mai 2007
Pat...... keep that up, and anybody on dial-up will get peeved! LOL 1MB download on your "loop"...... 3-5 minute download on dial-up.... course I think we do have an image-less blog also don't we?? If I were dial-up, thats what i would be looking at! but I guess as long as nobody complains....... Member Since: 8 septembre 2005 Posts: 0 Comments: 3748

1017. Jedkins 14:49 GMT le 08 mai 2007
well you can't be sure, but local guys have rain season pattern here by friday into next week, which normally isn't till june. So maybe tropical weather is off to an early start. Hard to tell for sure just yet.

1018. thelmores 14:50 GMT le 08 mai 2007
"Very subjective" finally, somebody that gets my point! I say blue, you say green! LOL Member Since: 8 septembre 2005 Posts: 0 Comments: 3748

1019. seminolesfan 14:50 GMT le 08 mai 2007
EXTREMELY well put incongN!! ;) Member Since: 14 juin 2006 Posts: 0 Comments: 1726

1020. thelmores 14:52 GMT le 08 mai 2007
new blog!!!! Member Since: 8 septembre 2005 Posts: 0 Comments: 3748

1021. SCwxwatch 14:53 GMT le 08 mai 2007
Posted By: thelmores new blog!!!! Isnt it due anytime?

1022. Patrap 15:35 GMT le 08 mai 2007
..from 0930 am CST last entry 30 frame loop..The showers earler were taking on some banding organazation. But now .. in the latest few frames, its less organised and somewhat pocketed. It may however ,,get the structure going this afternoon. Time will tell Member Since: 3 juillet 2005 Posts: 372 Comments: 111617

1024. lightning10 03:17 GMT le 09 mai 2007
RIP griffiths observatory. Record heat + wind + DRYEST SEASON TO DATE... Member Since: 24 novembre 2005 Posts: 41 Comments: 629

1025. stormwatcher247 01:12 GMT le 10 mai 2007
So, what's the remainder of the tropics look like?

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