Dr. Jeff Masters' WunderBlog

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

Posted by: Dr. Jeff Masters, 02:42 PM GMT del 07 Maggio 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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3. SavannahStorm 02:50 PM GMT del 07 Maggio 2007
Conditions at 41001 as of (9:50 am EDT) 1350 GMT on 05/07/2007 Wind Direction (WDIR): ENE ( 70 deg true ) Wind Speed (WSPD): 36.9 kts Wind Gust (GST): 46.6 kts Wave Height (WVHT): 40.7 ft 40 Foot Waves!!! Member Since: Settembre 22, 2005 Posts: 18 Comments: 2135

4. HCW 02:54 PM GMT del 07 Maggio 2007
INVEST 90L look for model runs to be posted very soon Hardcoreweather.com Member Since: Agosto 10, 2002 Posts: 0 Comments: 1280

5. HadesGodWyvern 02:55 PM GMT del 07 Maggio 2007
ST2.5/2.5 Satellite Service Division has a fix on the system whether its tropical or not.. Member Since: Maggio 24, 2006 Posts: 43 Comments: 36686

6. IKE 02:58 PM GMT del 07 Maggio 2007
Thanx for the update Dr.Masters...come on 90L...head west/SW and bring some rain to the parched SE USA. It's no fun mowing grass and having dirt flying up everywhere from it being so dry. Head west young lady! Member Since: Giugno 9, 2005 Posts: 23 Comments: 37044

7. thelmores 02:59 PM GMT del 07 Maggio 2007
I see Ike has engaged into westcasting with me! WEST 90L, GO WEST! LOL we need rain!!! Member Since: Settembre 8, 2005 Posts: 0 Comments: 3748

8. SavannahStorm 03:00 PM GMT del 07 Maggio 2007
Joe Bastardi thinks it will go warm core: SUNDAY 10:30 A.M. THE CASE FOR CONVERSION TO WARM CORE. In a way, the GFS is saying this will happen. One has to remember that warm core would mean dry subsiding air in the middle of a storm that is surrounded by air that is cooler. The mechanism to sustain the storm then becomes forced, rather than baroclinically induced. In other words, at first it is the mixing of cold and warm air in a way that causes upward motion to develop the storm, but once the storm develops and the temperature gradient fades, the input of energy is driven by strong long-level winds over warm moist water that rises as it approaches the center. This releases heat up and out of the storm, but an areas of sinking develops in the center of storm because of the air going up so quickly as it approaches. The process is helped along by the existence of dry air anyway which, like gulls in the eye of the storm, gets caught there, so we open up the dry center. The conversion to a warm core system is one that has always been a mystery and causes great wailing and gnashing of teeth. For instance, Karen a few years ago blasted Bermuda, but was not declared a tropical cyclone until the recon got in and found out what many of us knew, that no storm causing winds to 80 mph over 83-degree water in September is cold core, even though its origins were. The solution of course is to develop a result-based criteria; in other words, closed rotary circulation with sustained gales in one quad over water warmer than 25c, name it. Chances are with that type of convergence to cause that, over water that warm, if it's not warm core, it will be soon. In addition, unsuspecting boaters in the warm water areas of our coasts will be warned in advance, as I am trying to do now for people along the southern Atlantic coast. The most interesting aspect as far as the GFS now goes is IT IS PREDICTING THIS TO BECOME WARM CORE. How so? 1) The fronts disappear. 2) It is moving it west-northwest and not in some small look but instead for a few hundred miles, so much so it actually takes it back to the coast. 3) It WEAKENS it as it reaches the cooler water and goes over land. Baroclinic systems usually move northeast and intensify with time not west-northwest and weaken as they hit land. From Accuweather Blog Post Member Since: Settembre 22, 2005 Posts: 18 Comments: 2135

9. IKE 03:01 PM GMT del 07 Maggio 2007
Hell yes..go west! Member Since: Giugno 9, 2005 Posts: 23 Comments: 37044

10. thelmores 03:04 PM GMT del 07 Maggio 2007
does anybody think JB knows what he is talking about?? sounds like accu-hype to me! :D Member Since: Settembre 8, 2005 Posts: 0 Comments: 3748

11. pseabury 03:05 PM GMT del 07 Maggio 2007
40 foot waves at 41001... Buoy 41001 Member Since: Maggio 28, 2005 Posts: 0 Comments: 3

14. thelmores 03:09 PM GMT del 07 Maggio 2007
hope the Canadian model plays out..... that looks like rain for the Carolina's! GO WEST I SAY, GO WEST 90L!!! Member Since: Settembre 8, 2005 Posts: 0 Comments: 3748

15. spiceymonster 03:12 PM GMT del 07 Maggio 2007
PIRSRON i am sorry but you are DEAD wrong, they had KATRINA going for the big bend of FLA, and where did it hit, um i think you need to rethink it. And the Wunderground folks NAILED the location of it too Member Since: Febbraio 10, 2002 Posts: 1 Comments: 158

16. thelmores 03:12 PM GMT del 07 Maggio 2007
rofl Gulf! we gonna lasso that sucka and bring it west! LOL Member Since: Settembre 8, 2005 Posts: 0 Comments: 3748

17. IKE 03:13 PM GMT del 07 Maggio 2007
All that's needed now is STORMTOP in here. It does appear to be drifting WSW...slowly. Head west 90L..... Member Since: Giugno 9, 2005 Posts: 23 Comments: 37044

18. IKE 03:16 PM GMT del 07 Maggio 2007
Looks like A Flock Of Seagulls...heading toward the SE USA....Link Member Since: Giugno 9, 2005 Posts: 23 Comments: 37044

19. SavannahStorm 03:18 PM GMT del 07 Maggio 2007
The only reason Accu didn't forecast Katrina going to LA is because they are anti-westcasting over there. Member Since: Settembre 22, 2005 Posts: 18 Comments: 2135

20. thelmores 03:21 PM GMT del 07 Maggio 2007
"and I ran..... I ran so far away....." Member Since: Settembre 8, 2005 Posts: 0 Comments: 3748

21. melwerle 03:36 PM GMT del 07 Maggio 2007
Funny - when it's a BAD storm, we all route for it to go the other way...in this case (so far) we're all routing for it to come OUR way. HIT SAVANNAH! I'm routing for it - NEED RAIN. Our lawn is terribly brown and I have lost a bunch of plants already since I'm awful at watering. Member Since: Giugno 28, 2006 Posts: 12 Comments: 1837

23. melwerle 03:40 PM GMT del 07 Maggio 2007
Let me rephrase that...how about just hitting us with rain so we can have a bit of green here? Put out the fires and such. Any ideas on this thing? Member Since: Giugno 28, 2006 Posts: 12 Comments: 1837

24. StormJunkie 03:43 PM GMT del 07 Maggio 2007
Still has a ton of dry air getting in to the center. It has to cut that off, or the rain will only be a sporadic rain shield for some areas. Afternoon mel, good to see you. Breezy down there? Member Since: Agosto 17, 2005 Posts: 26 Comments: 15218

25. melwerle 03:48 PM GMT del 07 Maggio 2007
Hey SJ - yep - it's breezy but not that bad. It was worse a couple of weekends ago - gusts at 45. I actually went SAILING in that nonsense. My daughter is bugging me to go out this week in this but I think I will play it safe. Should the winds be getting stronger throughout the week? Member Since: Giugno 28, 2006 Posts: 12 Comments: 1837

27. StormJunkie 03:52 PM GMT del 07 Maggio 2007
Mel, maybe in rain bands, but the low should start weekening if the models are correct. The worst winds should remain off shore, but as the low approaches the coast, could see some 30+mph sustained winds. Can't believe you went sailing when we had those winds. That was a odd event. Windy as hell when that system passed through. Member Since: Agosto 17, 2005 Posts: 26 Comments: 15218

28. SavannahStorm 03:53 PM GMT del 07 Maggio 2007
Beware of the rouge waves- they might bring a blush to your cheeks. Member Since: Settembre 22, 2005 Posts: 18 Comments: 2135

29. melwerle 03:56 PM GMT del 07 Maggio 2007
yeah - it was pretty crazy. Kid had a BLAST - flipped the boat a couple of times but she was having a great time. Won't be doing THAT again. So when will they have a better grip on what this thing is or isn't? Later today? Tonight? Hey - great page btw SJ - you have everything on there. wooo hoooo! Member Since: Giugno 28, 2006 Posts: 12 Comments: 1837

30. StormJunkie 03:57 PM GMT del 07 Maggio 2007
lol SS. Next GFS run should be coming out soon. Other models to follow between one and two. Someone wundermail me with anything interesting the next GFS says. For some reason, can't view the NWS model page from work, can't use the SSD page either. Thanks, back to work! Quick Links-Easily find model pages, imagery, marine data, wind data, and much more. Member Since: Agosto 17, 2005 Posts: 26 Comments: 15218

32. StormJunkie 03:58 PM GMT del 07 Maggio 2007
Thanks mel :~) Maybe later tonight...Maybe. You will know for sure what it is going to do when it does it though...lol Morning GS...lmao... Member Since: Agosto 17, 2005 Posts: 26 Comments: 15218

33. Parkay 03:58 PM GMT del 07 Maggio 2007
I captured my own loop of the storm cluster spinning up and spreading out. Its not the same zoom in as Dr. Master's, but it gives you an idea of the scale of the system. Its a capture of all of the n0r reflectivity images on May 5 as they came in over my NOAAPORT feed. http://weather.psychoses.org/ddc-n0r-may5-radloop.gif Member Since: Aprile 21, 2005 Posts: 0 Comments: 28

34. melwerle 03:59 PM GMT del 07 Maggio 2007
Nap time for me...catch y'all later! Member Since: Giugno 28, 2006 Posts: 12 Comments: 1837

35. V26R 04:02 PM GMT del 07 Maggio 2007
Aren't Rouge Waves part of the red Menace? Member Since: Luglio 20, 2006 Posts: 0 Comments: 1759

37. V26R 04:07 PM GMT del 07 Maggio 2007
Whats Up CB? How Ya Been? Member Since: Luglio 20, 2006 Posts: 0 Comments: 1759

38. weathermanwannabe 04:08 PM GMT del 07 Maggio 2007
Hey all......We need a rainmaker for the SE so I hope it lingers around and sqeezes out the juice........... Member Since: Agosto 8, 2006 Posts: 0 Comments: 6695

39. lilmax 04:08 PM GMT del 07 Maggio 2007
Thanks Dr. M.

40. V26R 04:09 PM GMT del 07 Maggio 2007
LilMax did you getthe Link for the Lightning Tracking site I posted for you last night? Member Since: Luglio 20, 2006 Posts: 0 Comments: 1759

42. V26R 04:15 PM GMT del 07 Maggio 2007
Closest Bouy at Frying Pan Sholes showing about 68 degs. Theres another one that I think could be closer to the Center but its OOS Link Member Since: Luglio 20, 2006 Posts: 0 Comments: 1759

43. fredwx 04:17 PM GMT del 07 Maggio 2007
NWS High Seas Forecast has a warning for Hurricane Force Winds: NORTH ATLANTIC NORTH OF 31N TO 67N AND WEST OF 35W. SYNOPSIS VALID 1200 UTC MAY 07. 24 HOUR FORECAST VALID 1200 UTC MAY 08. 48 HOUR FORECAST VALID 1200 UTC MAY 09. .WARNINGS. HURRICANE FORCE WIND WARNING .LOW 32N 73W 998 MB MOVING SW 10 KT. OVER FORECAST WATERS...WINDS 55 TO 70 KT SEAS 26 TO 39 FT BETWEEN 60 NM AND 180 NM N SEMICIRCLE. ELSEWHERE WINDS 40 TO 55 KT SEAS 18 TO 28 FT WITHIN 300 NM N SEMICIRCLE. WINDS 25 TO 40 KT SEAS 12 TO 24 FT ELSEWHERE FROM 31N TO 39N W OF 62W. .24 HOUR FORECAST LOW MOVED S OF AREA NEAR 30N 77W 1002 MB. FORECAST WINDS 40 TO 50 KT SEAS 16 TO 28 FT WITHIN 240 NM N QUADRANT OVER FORECAST WATERS. ELSEWHERE FORECAST WINDS 25 TO 40 KT SEAS 12 TO 22 FT FROM 31N TO 38N W OF 68W. .48 HOUR FORECAST LOW 31N 79W 1005 MB. FORECAST WINDS 25 TO 40 KT SEAS 11 TO 18 FT FROM 31N TO 34N W OF 71W. Member Since: Giugno 8, 2005 Posts: 221 Comments: 261

44. Jedkins 04:17 PM GMT del 07 Maggio 2007
And no, the Carolinas don't need the rain that much, Florida does, Lake Okee is at record low leves, heavy storms last 2 days has brought it back up just a bit, but we need alot more, yes the rain season is almost here, but its still about 3 weeks away on average, and with the strong Florida sun, thats plenty time to dry things up much further.

45. V26R 04:17 PM GMT del 07 Maggio 2007
Gotta get back to work, Talk to you later CB Mike Member Since: Luglio 20, 2006 Posts: 0 Comments: 1759

46. Jedkins 04:18 PM GMT del 07 Maggio 2007
And also, its not heading wsw, use your eyes, its moving south-southwest, as it has since last night.

47. Jedkins 04:20 PM GMT del 07 Maggio 2007
Oh and there is some convective activity on the west side of the center, but its not deep moit tropical convection found in warm core yet, this thing is over too cool of water at this time to begin transition just yet. Its chances to do so will not apply till tommorrow folks please don't overhype, be civilized.

48. rxse7en 04:20 PM GMT del 07 Maggio 2007
"I'll catch this bird for you, but it ain't gonna be easy." Member Since: Agosto 21, 2005 Posts: 0 Comments: 526

50. thelmores 04:24 PM GMT del 07 Maggio 2007
looks like we finally have some thunderstorms firing on the west side...... GO WEST!! GO WEST!! Member Since: Settembre 8, 2005 Posts: 0 Comments: 3748

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