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Another wild night in Tornado Alley

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

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

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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834. BahaHurican
6:14 AM EDT on May 07, 2007
Morning all,

Would u believe it's barely rained here? That blob just fizzled out as it crossed the Gulf Stream. However, I just heard a bit of thunder, so perhaps later this a. m. we will get a bit of rain. Meanwhile, the temperature has really dropped; it feels almost 10 degrees cooler out there than it did yesterday morning around this time . . .

I'm out for the day. Have a good one! (hope nobody gets hit with another tornado)
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833. lilmax
10:12 AM GMT on May 07, 2007
Hello everyone. Those 7 hours of sleep really did me well.
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832. StoryOfTheCane
9:20 AM GMT on May 07, 2007
who knows what it will be, just take note that a disturbance is in the forecast
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831. TayTay
8:55 AM GMT on May 07, 2007
Doesn't look like it will even become subtropical. It's just a gale.
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830. StoryOfTheCane
8:48 AM GMT on May 07, 2007
check out the Southern Caribbean around May 14th on the GFS:MSL:Tropical Atlantic:18z, could affect the islands before heading out to sea
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829. Starwoman
10:40 AM CEST on May 07, 2007
Thanks, GR. I thought something like that would happen but wasn't sure (as I'm new to forcasting).
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828. GetReal
8:33 AM GMT on May 07, 2007
Star the dry continental air entraining into the system will hinder the development of heavy convection. Consequently the system will be less likely to become a true tropical system... Sub-tropical maybe with time... It currently has the look of a cold core low (Gale center).
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827. Starwoman
10:25 AM CEST on May 07, 2007
Would the dry air hinder the development?
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826. StoryOfTheCane
6:45 AM GMT on May 07, 2007
buoy reading 48kts, 60kt gusts. 29.69in/.05 (Rising). a lot of spin in there but not a whole lot of convection, its sucking in a bunch of dry air.

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825. Starwoman
8:37 AM CEST on May 07, 2007

Significant Wave Height (WVHT): 32.2 ft
Swell Height (SwH): 28.9 ft
Swell Period (SwP): 14.3 sec
Wind Wave Height (WWH): 13.5 ft
Wind Wave Period (WWP): 5.9 sec
Average Wave Period (APD): 9.9 sec
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824. franck
6:30 AM GMT on May 07, 2007
What about the wave heights??!!
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822. strong
5:22 AM GMT on May 07, 2007
I'm no expert at weather, but from what I have seen ,a jet stream over a thunder storm
will give you much higher odds of a tornado manifesting, and on the other hand, a thunder
storm with no jet stream with in , lets say 500
miles will have a slim chance of producing a tornado! is this a fairly true statment?
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5:26 AM GMT on May 07, 2007
Statement as of 12:07 PM CDT on May 07, 2007
The National Weather Service in San Angelo has issued a
* Tornado Warning for...
southern Irion County in southwest Texas...
* until 1245 am CDT

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817. Skyepony (Mod)
4:29 AM GMT on May 07, 2007
Not only has this year's tornado fatalities surpased last year's total it has surpased the 10 year average of 62 & the 30 year average of 54 & we're not even 1/2 through the year yet.
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816. MZT
4:26 AM GMT on May 07, 2007
Hmm, getting easy to spot the center of circulation now...

-Dang- it's workday tomorrow. Guess I'll check up on it in the morning, to see what happened overnight!
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815. MZT
4:10 AM GMT on May 07, 2007
Bouy 41013 is no slouch either... windspeeds are just touching 39 mph .. tropical storm boundary strength.

Even bouy 41012 off the coast of northern FLA is registering 9 foot waves and 30 mph winds. Tropical or not, this is a strong storm.
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812. MZT
3:57 AM GMT on May 07, 2007
Another storm that the Southeast "thing" looks like is hurricane Gordon from Y2000. Messy commas can be tropical...

Gordon 2000
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811. Jedkins
3:48 AM GMT on May 07, 2007
Rainfall total estimates are way below what they actually are in soth Florida, areas in south Florida(like Miami) that have rain guages reported totals as high as 3 inches when radar estimated only 1.5 maximum.

In fact Miami reported 2.90 inches in a half hours time, pretty darn heavy.
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810. MZT
3:38 AM GMT on May 07, 2007
The Atlantic storm may still be a comma shape, but it's fattening up nicely on the shortwave loops.

Ya know, to be honest, I think it's starting to look a lot like Alberto on the infrared.
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808. RL3AO
9:53 PM CDT on May 06, 2007
Definatly a tornado on the ground in Pecos county.

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805. Bamatracker
2:48 AM GMT on May 07, 2007
o...k... things are just getting wierd in here now.
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802. TheCaneWhisperer
10:43 PM EDT on May 06, 2007
Evening all! Seems the models are pushing the low off the East Coast a little further south! Keep it coming, we need the rains down here!
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800. KoritheMan
2:42 AM GMT on May 07, 2007
Would SOMEONE PLEASE mail me and tell me what TUNNELS are??
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799. seminolesfan
2:42 AM GMT on May 07, 2007
f-this; nite all!!!!
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798. seminolesfan
2:41 AM GMT on May 07, 2007
you need to be given your meds.
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796. stormhank
2:37 AM GMT on May 07, 2007
66 Hr 00Z NAM.. looks almost stationary?Link
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795. pottery
10:34 PM AST on May 06, 2007
Bahahurican, what are the sea conditions there now ?
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794. hurricane23
10:35 PM EDT on May 06, 2007
Right now the NHC has at 1005mb area of low pressure.We'll see what happens over the next day or two.

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793. seminolesfan
2:30 AM GMT on May 07, 2007
buster-I remember when the admins 'requested' that you leave the tunnels out of the underground ,if you'll pardon the pun.

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792. Bamatracker
2:31 AM GMT on May 07, 2007
well that looks the same...looks like the low is starting to wrap a little
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791. BahaHurican
10:25 PM EDT on May 06, 2007
If u want a satellite closeup of that cell as it moves off the FL coast, go here.

I notice it seems to be losing power as it slides off the coast, but it still has enough oomph to it it (hopefully) give us a good night's rain shower. I did check car windows and house windows just now to make sure nothing got wet.

One of the advantages of living in the islands is that tornados rarely form here and even more rarely do damage on land. Mostly we see waterspouts, and the rare tornado is usually embedded in a hurricane.
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790. stormhank
2:31 AM GMT on May 07, 2007
new 00Z NAM 48hr..Link
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788. lilmax
2:24 AM GMT on May 07, 2007
I'm tired people, all this watching loops of the future system in the Atlantic, watching Tornado Warnings pop up in my side of town and tracking the severe weather in the Central Plains has made me tired. Good night everyone and be safe.
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787. pottery
10:25 PM AST on May 06, 2007
" use our tunnels
to stop those funnels " tm

I'm the marketing dept....................
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786. KoritheMan
2:25 AM GMT on May 07, 2007
I'm sorry if I started anything by asking. Can't someone MAIL me and tell me? I'm really curious.
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785. Bamatracker
2:25 AM GMT on May 07, 2007
nnooooooooooooooooo....dont ask about the tunnels!!!! LOL
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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