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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84. scottsvb
3:24 PM GMT on May 06, 2007
hurricane23 if the system heads back more sw by later thurs and friday..its cause it will be weaker and go with the LLF from the surface ridge over the SE US. Not sure if you were thinking there was a upper ridge...cause there wont be! It may acquire LL tropical characteristics to call it subtropical storm Andrea...but its a wait and see....but it will take a few days.
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83. Drakoen
3:21 PM GMT on May 06, 2007
Its interesting that at this time of the year we could be looking a rapid cyclogenisis. HMM what will the future hold. Wherever the systems goes i hope that it will at least bring beneficial rains. If it were to take the southern track with the high remaining storng in the northeast. It would weaken as it go to south florida probably tropical depression strength if that. That would bring some much needed rain to South Florida as we are exceptionally dry, Especially where i live in Palm Beach county.
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82. Drakoen
3:17 PM GMT on May 06, 2007
Right now I am looking at 4 models the cmc and GFS taking it into Georgia-South Carolina and then the other two models the UKMET and the NOGAPS taking it into MID-SOUTHERN Florida. Where do we draw the line?
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81. hurricane23
11:18 AM EDT on May 06, 2007
Are more models coming into agreement that it will hit Florida?

More like a loop, then into SC. I wouldn't call it agreement yet, either. Still waitin' on some more of the 12z models.

12z models will be interesting but the GFS maybe under estimating the strength of the high.
Member Since: May 14, 2006 Posts: 8 Comments: 13841
80. crownwx
11:18 AM EDT on May 06, 2007
I have posted satellite, radar, surface and weather advisory information regarding the southeast US storm on our Tropical Weather Page, found HERE
Member Since: December 27, 2004 Posts: 3 Comments: 207
79. HurricaneRoman
3:19 PM GMT on May 06, 2007
oh and i live in south Broward by the way
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78. HurricaneRoman
3:16 PM GMT on May 06, 2007
yes..of course u can report severe weather..... I triggered a severe thunderstorm warning b4 ;D .... it was pretty coool...there was like quarter size hail and gust to like 60 and there was no warning so i called in and less then 5 minutes after they issued a warning and put my reprt on the weather channel and the news and all that stuff..... but yeah whenever i get wevere weather i rpeort it ...and u should ,i t could save someones life mayb
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77. seminolesfan
3:14 PM GMT on May 06, 2007
Are more models coming into agreement that it will hit Florida?

More like a loop, then into SC. I wouldn't call it agreement yet, either. Still waitin' on some more of the 12z models.
Member Since: June 14, 2006 Posts: 0 Comments: 2108
76. Drakoen
3:13 PM GMT on May 06, 2007
Are more models coming into agreement that it will hit Florida?
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75. Dakster
3:12 PM GMT on May 06, 2007
I don't think they directly correlate to one another, as both have many factors that influence there respective activities. For one, "Tornado" season (if there really is such a definite time frame) seems to occur outside of the official "Hurricane Season" Therfore, large scale weather patterns can (and do) change. So many other factors that influence Hurricane development do not influence tornado development. (Saharan Dust Layer, Shear, etc...) AND vice versa.

Any correlations would be coincendences, in my humble opinion. I do not hold any degress related to weather forecasting, etc... This is information I have picked up over the past few years of reading this blog... I could be completely wrong.
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74. lilmax
3:03 PM GMT on May 06, 2007
I'm not a trained spotter, but I can still report severe weather, correct?
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73. lilmax
2:59 PM GMT on May 06, 2007
000
FLUS42 KMFL 061421
HWOMFL

HAZARDOUS WEATHER OUTLOOK FOR SOUTH FLORIDA
NATIONAL WEATHER SERVICE MIAMI FL
1021 AM EDT SUN MAY 6 2007

FLZ063-066>075-070200-
GLADES-HENDRY-PALM BEACH WESTERN-PALM BEACH EASTERN-
WESTERN COLLIER-EASTERN COLLIER-WESTERN BROWARD-
BROWARD METROPOLITAN-WESTERN DADE-DADE METROPOLITAN-
MAINLAND MONROE-
1021 AM EDT SUN MAY 6 2007

...STRONG TO SEVERE THUNDERSTORMS POSSIBLE THIS AFTERNOON...
...WINDS AND SEAS TO INCREASE TONIGHT OVER LOCAL WATERS...
...ROUGH SURF CONDITIONS EAST COAST MONDAY THROUGH WEDNESDAY...
...RIP CURRENTS EAST COAST BEACHES MONDAY THROUGH THURSDAY...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH FLORIDA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS: SCATTERED THUNDERSTORMS WILL DEVELOP OVER INTERIOR
MAINLAND SOUTH FLORIDA THIS AFTERNOON. FREQUENT LIGHTNING STRIKES
WITH GUSTY WINDS, HAIL AND LOCALLY HEAVY RAINFALL CAN BE
EXPECTED. THUNDERSTORMS WILL LIKELY LAST INTO THE EVENING HOURS AS
A COLD FRONT MOVES SOUTH ACROSS THE REGION.

TORNADOES: A TORNADO OR TWO MAY BE POSSIBLE WITH ANY THUNDERSTORM
THAT DEVELOPS THIS AFTERNOON AND EVENING...ESPECIALLY ANY STORM
THAT FORMS ALONG THE SEA BREEZES.

HAIL: STRONG INSTABILITY WILL BE IN PLACE THIS AFTERNOON ACROSS
THE REGION...AND THE STRONGER THUNDERSTORMS MAY PRODUCE HAIL OVER
PENNY SIZE THIS AFTERNOON AND EVENING.

WIND: DUE TO RELATIVELY DRY AIR IN THE MID LEVELS OF THE
ATMOSPHERE...ANY THUNDERSTORM IS CAPABLE OF PRODUCING WIND GUSTS
OVER 50 MPH.

IN ADDITION...A COLD FRONT WILL MOVE ACROSS THE LOCAL AREA
TONIGHT. AS A RESULT...NORTHEASTERLY WINDS WILL INCREASE WITH
FREQUENT GUSTS OVER 30 KNOTS AND SOME GUSTS TO 40 KNOTS. THIS
THREAT WILL BEGIN JUST AFTER MIDNIGHT ACROSS LAKE OKEECHOBEE AND
THE NORTHERN ATLANTIC WATERS...AND SPREAD SOUTH THROUGH THE
REMAINDER OF THE ATLANTIC WATERS AND THE GULF WATERS BY MORNING.

FLOODING: STEERING WINDS ALOFT, THOUGH A LITTLE STRONGER TODAY, WILL
STILL ALLOW LOCALLY HEAVY RAINFALL AT A FEW LOCATIONS, RESULTING IN
POSSIBLE PONDING OF WATER IN LOW LYING OR POORLY DRAINED AREAS.

WAVES: STRONG SUSTAINED NORTHEAST WINDS OF 20 TO 25 KNOTS WITH
GUSTS OF 30 TO 40 KNOTS WILL INCREASE GULF STREAM SEAS TO 7 FEET OF
HIGHER BY LATE TONIGHT.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

NORTHEAST WINDS OF 20 TO 25 KNOTS MONDAY WILL INCREASE THE RISK OF
RIP CURRENTS AT THE ATLANTIC BEACHES OF SOUTH FLORIDA. MODERATE TO
LARGE NORTHEAST SWELLS MOVING SOUTH THROUGH THE ATLANTIC WATERS WILL
ALSO KEEP THE RISK OF RIP CURRENTS ELEVATED FOR THE ATLANTIC BEACHES
TUESDAY THROUGH THURSDAY.

THE SWELLS WILL ALSO INCREASE THE SEAS IN THE GULF STREAM TO 10 TO
13 FEET BY MONDAY NIGHT INTO TUESDAY, BEFORE SLOWLY SUBSIDING TO
LESS THAN 7 FEET BY LATE THIS WEEK. NEARSHORE SEAS WILL ALSO BUILD
TO 7 TO 10 FEET DURING THIS PERIOD...ESPECIALLY ALONG THE PALM
BEACH COUNTY COAST. THE SWELLS WILL ALSO INCREASE THE ROUGHNESS OF THE
SURF WITH POSSIBLE MINOR BEACH EROSION AT TIMES OF HIGH TIDE EARLY
NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO REPORT ANY OBSERVED HAIL AND GUSTY
WINDS OVER 50 MPH FROM THUNDERSTORMS THIS AFTERNOON AND EVENING.

FOR MORE INFORMATION...VISIT THE NATIONAL WEATHER SERVICE IN
MIAMI WEBSITE AT WWW.WEATHER.GOV/MIAMI.
$$

What's going on here, are we truly in that time of year where "pop-up" thunderstorms start to form?
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72. ajcamsmom
9:57 AM CDT on May 06, 2007
OK, so what you all are telling me is that all this horrible weather activity that is going on now has no real bearing on the upcoming hurricane season???
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71. ajcamsmom
9:51 AM CDT on May 06, 2007
Taz...thanks for the pictures...those poor people...they need all the help they can get
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70. HurricaneRoman
2:51 PM GMT on May 06, 2007
Whoa thats crazy, its so early in the season.... and it looks large, hmmmmm......
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69. Dakster
2:31 PM GMT on May 06, 2007
NHC Floater 1 is on the system here:

Link

Is that a high level center I see trying to form? It appears to be going SE away from South Carolina...

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68. DocBen
2:48 PM GMT on May 06, 2007
h-23 - what are the numbers in red on the map? They don't seem to follow the isobars.
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67. Tazmanian
7:44 AM PDT on May 06, 2007
photos of what ues to be Greensburg now by looking at this i say EF5
lol

lol

lol

lol

Downtown Greensburg lies in ruins

lol

lol
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
66. weatherboykris
2:48 PM GMT on May 06, 2007
Nice Adrian.BBL guys.Can't wait for the 12z globals.
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65. hurricane23
10:47 AM EDT on May 06, 2007
Closer view of the NAM and UKMET...

NAM-

G

UKMET-

G
Member Since: May 14, 2006 Posts: 8 Comments: 13841
64. seminolesfan
2:46 PM GMT on May 06, 2007
More info from the NWS, this is from the Melbourne office:

LOW PRESSURE AREA STARTING TO TAKE SHAPE OFF
THE SOUTH CAROLINA COAST EARLY THIS MORNING. PGRAD INITIALLY WEAK
THIS MORNING WITH LIGHT WINDS. THE LOW OFFSHORE WILL BEGIN TO DEEPEN
MORE RAPIDLY BY THIS AFTERNOON AND ESPECIALLY TONIGHT WITH STRONG
SHORTWAVE PUSHING ACROSS THE MID ATLANTIC COAST TODAY WITH RAPID
CYCLOGENESIS OCCURRING TONIGHT.
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63. ajcamsmom
9:42 AM CDT on May 06, 2007
All I can say is that whatever it is...I hope it stays out of the GOM!
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62. CrazyC83
2:35 PM GMT on May 06, 2007
Tornado activity and hurricane activity are not related; the 2005 spring tornado season was very quiet...and until November, there was only one significant outbreak not caused by a tropical storm or hurricane (August 18 in Wisconsin)...
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61. seminolesfan
2:37 PM GMT on May 06, 2007
From NWS Tallahassee:

LATEST GUIDANCE PUSHING SURFACE AND UPPER
LEVEL SYSTEM BACK TOWARD THE SOUTHEAST COAST LATER TUESDAY INTO
WEDNESDAY. WHILE THIS BUTS UP AGAINST CLIMATOLOGY WHICH IMPLIES THAT
THE UPPER RIDGE WOULD BE ABLE TO HOLD THIS SYSTEM OFFSHORE...HARD TO
GO AGAINST ALL NUMERICAL GUIDANCE.


How's this for a hedge-betting forcast?
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60. weatherboykris
2:40 PM GMT on May 06, 2007
This should be sub-1000mb.
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59. MZT
2:37 PM GMT on May 06, 2007
I suspect a 1000 millibar storm will get named, if it just looks "moderately tropical" and has a warm core.

Heck, Alberto was in the 1002-1003 millibar range as he approached Florida.
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58. weatherboykris
2:38 PM GMT on May 06, 2007
With a Jeanne like loop.
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57. weatherboykris
2:36 PM GMT on May 06, 2007
The models are starting to bring it closer to FL.
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56. weatherboykris
2:36 PM GMT on May 06, 2007
Very interesting adrian.
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55. hurricane23
10:35 AM EDT on May 06, 2007
Interesting kris....


g
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54. MZT
2:28 PM GMT on May 06, 2007
The models seem to think this will transition to warm core pretty quickly. If so, it could begin looking tropical tomorrow morning...
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53. weatherboykris
2:25 PM GMT on May 06, 2007
The UKMET has it taking a loop in the FL direction:

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52. MZT
2:25 PM GMT on May 06, 2007
We had a few "teaser" events off the Atlantic coast last year... storms that ultimately were not tropical enough or strong enough to name. It's not THAT unusual to be playing this guessing game in May/June.
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51. ajcamsmom
9:18 AM CDT on May 06, 2007
I can hardly believe we are looking at anything in the Atlantic this early...hope it is not a warning of things to come...hope it is more of an initial blast before the storm season fizzles and dies for yet another year...I really would like a repeat of 2006, still not on my feet from Katrina and Rita...but, with the Tornado's, the warm waters, the forecasted lowering of the shear & African Dust...well, I am stocking up on water and keeping my car gassed up.
Lisa
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50. weatherboykris
2:22 PM GMT on May 06, 2007
H23,the NAM is also now saying it could head towards FL.Check what's out so far of the 12z.
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49. hurricane23
10:19 AM EDT on May 06, 2007
Becareful SST'S are almost at 80 degrees near the gulfstream and if it manages to slip to the south as the nogaps and a few other models show it may try to make a run at sub-tropical and may get a name.

SST'S
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48. weatherboykris
2:13 PM GMT on May 06, 2007
WRF and NAM are the same model.
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47. StormJunkie
2:07 PM GMT on May 06, 2007
Morning all.

AS for the SSTs, the Gulf Stream waters look to be at above the 26c mark all the way up to the OBX. It is also interesting to note that the area where this low will be does look warmer then it has been in the past 3 years at this time of year. You can see this in the year to year SST comparison maps in my blog. The previous year maps are from May 15. This years map is from today.
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46. weathersp
10:10 AM EDT on May 06, 2007
The last 12z run the WRF,GFS and the NAM had come to about the same concluion of 1000-1002mb off SC coast.
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45. seminolesfan
2:09 PM GMT on May 06, 2007
Next discussion from NHC is @ 2pm EST
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44. weatherboykris
2:09 PM GMT on May 06, 2007
Not until June 1st,Drakoen.
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43. Drakoen
2:06 PM GMT on May 06, 2007
The SST's are just a bit low but i think that the shear will come down based on the forecast. Does the NHC give out an 11:00 am overview of the atlantic?
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42. MZT
2:00 PM GMT on May 06, 2007
Non-tropical would make more sense. It is *quite* cool for May. Lows in the low 40s the next few nights forecast for Charlotte.

We'll see. It may still be an interesting hybrid storm.
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41. weatherboykris
2:06 PM GMT on May 06, 2007
Posted By: seminolesfan at 2:01 PM GMT on May 06, 2007.

Arn't they forced to by federal law now? Only pass on NWS forcasts I mean.


No.They're forced to by their lack of ability.LOL
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40. Drakoen
2:01 PM GMT on May 06, 2007
Posted By: weatherboykris at 2:01 PM GMT on May 06, 2007.

The only time TWC is interesting is when one of their experts are talking.Steve Lyons or Greg Forbes.


I don't think so there all pretty much the same, being conservative. Sometimes you might hear interesting things from them though, that actually follow through. We won't here from Steve Lyons untill june 1st.
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39. seminolesfan
1:57 PM GMT on May 06, 2007
Arn't they forced to by federal law now? Only pass on NWS forcasts I mean.
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38. chessrascal
2:00 PM GMT on May 06, 2007
lol
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37. weatherboykris
2:00 PM GMT on May 06, 2007
The only time TWC is interesting is when one of their experts are talking.Steve Lyons or Greg Forbes.
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36. weatherboykris
1:59 PM GMT on May 06, 2007
Well would you look at that,huh Skye.Very interesting.
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35. Drakoen
1:58 PM GMT on May 06, 2007
yea thats what i think they just copy information they get. Makes the weather channel even more fake. At least this low will give us something to watch and pass the time till hurricane season begins.
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34. hurricane23
9:49 AM EDT on May 06, 2007
Guys forgot to post this check this out!!Must see video of the F5-F4 tornado on ground in Greensburg .

Video here
Member Since: May 14, 2006 Posts: 8 Comments: 13841

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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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