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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884. Patrap
8:35 AM CDT on May 07, 2007
6
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883. sporteguy03
1:32 PM GMT on May 07, 2007
Why would it weaken before hitting land? I thought it needs to hit land to weaken??
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882. Skyepony (Mod)
1:14 PM GMT on May 07, 2007
It isn't an invest. If this was any other basin save the EPAC perhaps...

As for the models 06Zgfs, 00Z NOGAPS, UKMET, MRF & ECMWF all take it over & or disapate it in FL (mostly Northern to central).

CMC & GEM has it meander NFL, GA, SC & out to sea.

A TD looks a little less likely. Maybe STD.
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879. crownwx
9:27 AM EDT on May 07, 2007
Do u have a link to the SSD classification of a 2.5 for this system?
Member Since: December 27, 2004 Posts: 3 Comments: 207
878. Thundercloud01221991
1:29 PM GMT on May 07, 2007
LOOK AT THIS

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877. StormJunkie
1:27 PM GMT on May 07, 2007
Morning all.

Thel, with the size of that rain shield, we may be able to get some. System really needs to get that dry air out though if it is to become much.

Quick Links - Models, imagery, marine data, and more.
Member Since: August 17, 2005 Posts: 26 Comments: 15626
876. thelmores
1:25 PM GMT on May 07, 2007
what does the storm off the SE coast need to become named??? I guess we are looking for tropical characteristics???

we certainly have winds that support a named storm! and 37foot waves to boot!
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875. Patrap
8:27 AM CDT on May 07, 2007
LSU Earth Scans Lab
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874. hurricane23
1:26 PM GMT on May 07, 2007
Good morning....

Checking in from work and everything looks like we will indeed have sub-tropical storm in our hands pretty soon.Be back in 3 hours.

gggg
Member Since: May 14, 2006 Posts: 8 Comments: 13621
873. Snowfire
1:16 PM GMT on May 07, 2007
It'a official--Greensburg has been classified as EF-5. Maximum winds estimated at 205 mph.
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872. ForecasterColby
1:15 PM GMT on May 07, 2007
By the way, since my site has become overwhelmed with spambots, I'll be posting my thoughts in my blog. Posting 90L statement momentarily.
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871. K8eCane
1:15 PM GMT on May 07, 2007
90L yay!
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870. ForecasterColby
1:14 PM GMT on May 07, 2007
NRL hasn't posted it as 90L yet, but this T-number came in an hour or so ago from SSD:

07/1145 UTC 32.0N 73.1W ST2.5/2.5 90L -- Atlantic Ocean

So they're calling it 90L.
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869. K8eCane
1:12 PM GMT on May 07, 2007
LOLOL gulf
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868. Patrap
8:10 AM CDT on May 07, 2007
Privacy Policy
Disclaimer
NRL Monterey Marine Meteorology Division (Code 7500) Tropical Cyclone Page (Ver.4.16)
Development Team
NOTE: this page is short lived (10 m). DO NOT bookmark it or save it to Favorites. Instead, bookmark http://www.nrlmry.navy.mil/tc_pages/tc_home.html
No Active Storms
<-- You may select a previously archived storm from the list in the left frame
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865. thelmores
1:03 PM GMT on May 07, 2007
Colby, we have 90L now???
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864. seminolesfan
1:02 PM GMT on May 07, 2007
Your not saying that it is now an invest are you Colby?
Member Since: June 14, 2006 Posts: 0 Comments: 2108
863. Patrap
8:03 AM CDT on May 07, 2007
6
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862. seminolesfan
12:57 PM GMT on May 07, 2007
Anyone else see the 00z ECMWF? It's the first model I've seen that pushes this thing across FL and into the Gulf.

The others(CMC,NOGAPS,UKMET,GFS)I looked at are still going with the loop then moving off to the E or NE, so the concensus is NOT into the Gulf right now.

I just thought it was worth mentioning.
Member Since: June 14, 2006 Posts: 0 Comments: 2108
861. ForecasterColby
12:59 PM GMT on May 07, 2007
ST2.5 in from SSD on our new friend 90L!

Wooo hoo, let's get this show on the road, folks.
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860. thelmores
12:59 PM GMT on May 07, 2007
Station 41001 - 150 NM East of Cape HATTERAS
(7:50 am EDT)
Wind Direction (WDIR): ENE ( 70 deg true )
Wind Speed (WSPD): 42.7 kts
Wind Gust (GST): 52.4 kts
Wave Height (WVHT): 37.1 ft

37FT WAVES! LOL

THE SURF IS UP! LOL
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859. shoals
12:55 PM GMT on May 07, 2007
Check this out- a webcam in Rodanthe, NC. notorious area for erosion on Hatteras Island;
http://www.darenc.com/webcam/mirlo.php

I live in Hatteras and we had gusts over 60 mph late last night, still gusting over 40-50 mph this morning.
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858. K8eCane
12:55 PM GMT on May 07, 2007
lol right seminoles
stormtop uses all caps all the time
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857. seminolesfan
12:51 PM GMT on May 07, 2007
sprinkleb-if you're the anti-ST then you should completely avoid capital letters; don't worry we're listening, you don't have to yell. lol
Member Since: June 14, 2006 Posts: 0 Comments: 2108
856. K8eCane
12:50 PM GMT on May 07, 2007
ok sprinklebottom
are you gonna stay on WU this season?
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855. thelmores
12:49 PM GMT on May 07, 2007


morning all! :)

Very interesting indeed...... at least at this point, seems extra, or sub tropical, as it seems the highest winds are well removed from the center. Quite breezy in myrtle beach this morning.... Steady north wind at 10-15mph, with gusts to 30+......

will be interesting to watch this "storm" develop over the next couple days..... wish we could get a little rain outta this "sucka"......

could this be tropical storm Andrea??
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854. SPRINKLEBOTTOM
12:45 PM GMT on May 07, 2007
K8 I AM THE ANTI-STORMTOP. I AM THE KING OF C & P. EVERYTHING I SAY IS WRITTEN IN SAND. IN EVERY POST THERE WILL BE A MESSAGE IN THE MOST IRREVERENT WAY. I CARE BECAUSE I DON'T CARE
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853. Patrap
7:42 AM CDT on May 07, 2007
7
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852. K8eCane
12:34 PM GMT on May 07, 2007
ok sprinkle bottom
are you stormtop?
your name is just the opposite
stormtop/sprinklebottom
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851. rxse7en
8:12 AM EDT on May 07, 2007
Hope we get TD1 and it just dumps rain over Jax for a couple of days. So dry here.
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850. SPRINKLEBOTTOM
12:24 PM GMT on May 07, 2007
LEGITIMATE BLOB #1 IS HERE. MY SPIRIT SISTER ALTANTICA OCEAN IS WARM AND INVITING. SHEARING WINDS HAVE QUIETED TO LISTEN FOR THE COMING STORM. MOTHER EARTH HAS THROWN DRY AIR AT IT AND STILL IT COMES. IT HASN'T WARMED TO THE OCCASION, IT HASN'T AWAKENED AS THE BEAR DOES TO THE WARMING DAYS OF SPRING AND MAY NOT, BUT AS THE SERPANTS WHO'S BELLIES TRAVERSE THE DUST, WHERE THERE IS ONE THERE ARE MANY! - SPRINKLEBOTTOM
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849. StormJunkie
12:14 PM GMT on May 07, 2007
Back to work. See y'all later ☺
Member Since: August 17, 2005 Posts: 26 Comments: 15626
848. StormJunkie
12:13 PM GMT on May 07, 2007
Looks like it is trying to cutoff the dry air skye. Will be interesting to see if it can manage it during the daytime heating.
Member Since: August 17, 2005 Posts: 26 Comments: 15626
847. dnalia
12:07 PM GMT on May 07, 2007
Good morning StormJunkie.

We're finally getting the rain we so desperately needed. I just wish it didn't come with the weather we got last night. I was driving back up to Kendall from Homestead and saw lots of cloud to ground lightning (I'm sure this sparked off a few brush fires out in the Everglades), and the sky had a bit of a green tinge. by the time I got home the sky was black. Then I got the tornado warning for our area. It was a wild night.
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846. Skyepony (Mod)
12:11 PM GMT on May 07, 2007
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845. GetReal
12:06 PM GMT on May 07, 2007
Good morning SJ... I have to run the kids to school will BBL.
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844. StormJunkie
12:03 PM GMT on May 07, 2007
Thundercloud, you can find the models from that link I posted a couple of posts back.

Morning GR and Dnalia
Member Since: August 17, 2005 Posts: 26 Comments: 15626
843. GetReal
11:52 AM GMT on May 07, 2007
Dnalia it means that it will not be a very good beach day for swimming in the surf, unless your are a surfer!!!
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842. dnalia
11:39 AM GMT on May 07, 2007
So what does that mean in layman's terms?
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841. Bamatracker
11:21 AM GMT on May 07, 2007
WESTERN ATLANTIC...
ATTENTION REMAINS FOCUSED ON THE STRONG LOW PRES SYSTEM OFF THE
CAROLINA COASTLINE....ANALYZED 998 MB NEAR 33N72W. A BACK DOOR
COLD FRONT IS PROGRESSING SWD FROM THE LOW TO SOUTH FLORIDA.
SCATTERED SHOWERS WITH ISOLATED TSTMS WITH THE FRONT ARE MOSTLY
WITHIN 60NM EITHER SIDE OF THE FRONT...THOUGH MIAMI RADAR AND
LIGHTNING DATA DEPICT TSTMS ARE MORE SCATTERED BETWEEN SFL AND
THE SE BAHAMAS. THE MAIN IMPACT WITH THIS SYSTEM IS THE STRONG
WINDS AND LARGE SEAS AS A VERY TIGHT PRES GRADIENT HAS SET UP
BETWEEN THE LOW AND STRONG HIGH PRES OVER THE NORTHEAST STATES.
A STORM WARNING HAS BEEN POSTED FOR THE FAR NW PORTION OF THE
AREA AS DESCRIBED IN THE HIGH SEAS FORECAST. IN ADDITION TO THE
ALREADY VERY IMPRESSIVE FETCH...AS THE STORM MOVES SSW IT WILL
PROMOTE A CAPTURE FETCH TOWARDS THE BAHAMAS AND FLORIDA. THIS
WILL FURTHER ADD TO THE VERY LARGE N/NE SWELL EVENT. HIGH SURF
ADVISORIES HAVE THUS BEEN POSTED FOR MUCH OF THE SOUTHEAST
COAST...SEE STATEMENTS FROM LOCAL FORECAST OFFICES FOR MORE
DETAILS. FARTHER E...A 1008 MB LOW LOCATED NEAR 29N62W ATTACHED
IS EXPECTED TO DISSIPATE OVER THE NEXT 24 HOURS. SCATTERED TSTMS
ARE MAINLY E OF THE LOW N OF 26N BETWEEN 53W-61W.


7am central NHC discussion
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839. Thundercloud01221991
10:49 AM GMT on May 07, 2007
Here is a link to the 28 indicators for classifying tornadoes

Link
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838. Thundercloud01221991
10:48 AM GMT on May 07, 2007
If the storm can cut the dry air off it could become tropical very fast does anyone have a link to the latest models
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837. StormJunkie
10:40 AM GMT on May 07, 2007
Morning all.

If the SE coastal low is to start becoming tropical or sub tropical it would likely not start happening until later tonight. That being said, it will have to get rid of that dry air if it has any shot. Will still be interesting to watch the evolution of this low either way though.

See y'all later

Quick Links
Member Since: August 17, 2005 Posts: 26 Comments: 15626
836. lilmax
10:29 AM GMT on May 07, 2007
40 KTS gusts being recorded on Cape Hatteras.
835. lilmax
10:18 AM GMT on May 07, 2007
Yeah, sure looks like it might have a tough time becoming fully sub-tropical. With all that dry air, nah.
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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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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