Mile-wide tornado smashes Windsor, Colorado; plus, hurricane season commentary

By: Dr. Jeff Masters , 1:23 PM GMT on May 23, 2008

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A mile-wide tornado swept through Colorado between 11am and noon yesterday, ripping the roofs off buildings, tossing cars into the air, and killing at least one person in Weld County, northeast of Denver. Hail up to 2.75" in diameter accompanied the storm, which took an unusual north-northwesterly track , parallel to the Rocky Mountains north of Denver. Hardest hit was the town of Windsor, between Fort Collins and Greely, where damage appeared to be at least EF3. A local TV station took some impressive live video of the tornado, and a wunderground web cam video in Windsor, Colorado (Figure 1) caught the funnel as it passed east of the camera.


Figure 1.Webcam view looking east at 11:45am MDT in Windsor, Colorado as the tornado passed by. Note the golf ball-sized hail covering the ground. Image credit: windsorweather.com.

The Weather Underground's tornado expert, Rob Carver, had this explanation of yesterday's tornadoes:

Two low pressure systems over the Western U.S. were the cause of the severe weather outbreak of May 22. A strong upper-level low over the Great Basin formed a surface low in the lee of the Rockies, and brought a strong southerly mid-level jet over the Plains of Colorado and Kansas. As the surface low formed, it brought warm moist air northwards, forming a warm front. This warm air moved westward, rising with the terrain, causing thunderstorms to form. Once these storms formed, the juxtaposition of easterly flow at the surface with southerly flow aloft (i.e., wind shear) produced significant spin in the horizontal direction, which was tilted by the storms to vertical spin, which triggered the formation of tornadic thunderstorms. This movement of the warm front up the slope of the Rockies to help trigger tornadic thunderstorms is a rare occurrence.



Figure 2. Radar reflectivity image (top) of the Windsor, Colorado tornado at 11:45am MDT May 22, 2008. Note the classic hook-shaped echo associated with the tornado. Bottom: Doppler velocity image of the tornado, showing a small core of red and blue colors right next to each other, denoting strong winds towards and away from the radar, the classic signature of a tornado vortex. For those interested, we've saved an animation of the reflectivity and Doppler velocity.

Severe weather forecast
Severe weather is expected today over Kansas, Nebraska, and surrounding states. NOAA's Storm Prediction Center has placed portions of this area under its "Moderate Risk" category for severe weather, one step below its highest level of concern, "High Risk". Yesterday was also a "Moderate Risk" day, which SPC later upgraded to "High Risk" once the tornadoes started pounding Colorado. More severe weather is expected Saturday and Sunday over the Midwest as the upper-level low pressure system responsible moves slowly eastward. The Weather Underground Severe Weather page and Tornado page and WebCam page are good places to go to follow the severe weather. Also, tune in to the chase accounts and awesome storm photos from Wunderblogger Mike Theiss, who was in Kansas yesterday, and has posted many spectacular photos of yesterday's storms. According to Mike's blog:

Today Cloud 9 Tours saw 4 tornadoes and ONE developing almost overhead. We experienced winds over 100mph from the circulation of the meso that passed overhead as a cone tornado developed. Stay Tuned....


Possible development in the Eastern Pacific late next week
The past four days, the ECMWF model has been predicting the formation of a tropical storm in the the Eastern Pacific, just off the coast of Guatemala, around May 29. The GFS model has also been predicting something might develop, but in the Western Caribbean near Mexico's Yucatan Peninsula. The GFS has been rather inconsistent with its handling of this potential storm, and I am inclined to discount its forecast--especially since last night's long range runs of the NOGAPS, Canadian, and UKMET models all show development in the Eastern Pacific, not the Caribbean. All five models predict a northward shift in the jet stream and substantial relaxation in wind shear over the Eastern Pacific and Western Caribbean next week. It is common to see May tropical storms in the Eastern Pacific, and it would not be a surprise to see something develop there. I'd put the odds of something popping up in the Western Caribbean or Gulf of Mexico at less than 10%, though.

NOAA's seasonal hurricane forecast
NOAA issued its annual seasonal hurricane forecast yesterday, which I discussed in detail in yesterday's blog entry. Yesterday's forecast came out with a little more uncertainty attached to it than previous forecasts, which is a good thing. The media attention and fanfare that accompanies these forecasts is rather excessive, given the low skill they have. In fact, we don't even know if the NOAA forecasts have ANY mathematical skill, because they've never released a verification study of their forecasts. I doubt that the skill is very high--as Eric Berger of the Houston Chronicle pointed out in a blog yesterday, NOAA has blown its forecast of Accumulated Cyclone Energy (ACE) each of the last six years. NOAA held its usual press conference to announce the forecast; this year, it was held at the home of the NOAA Hurricane Hunter aircraft, MacDill AFB in Tampa. The NOAA dignitaries present said all the right things, preaching the need for preparedness regardless of the forecast for the upcoming hurricane season. Still, I wonder if NOAA might be hurting themselves by making such a public spectacle over the release of a forecast that no one knows the accuracy of, and has performed poorly by some measures in recent years. I do like the fact they are issuing public hurricane forecasts, as I expect their accuracy and value will improve in coming years, but they're definitely not worth the attention they're getting at present.

Jeff Masters

Tornado1 (kd7tda)
One of several tornados. This one was near Grainfield, KS
Tornado1
Tornado Damage 3 (jlg)
Damage from today's Tornado in Windsor, Colorado
Tornado Damage 3
()
Mean Looking Meso with Cone Tornado (MikeTheiss)
Photo os a wallcloud with a developing tornado passing just to the north of our location on May 22nd, 2008. Photo copyright Mike Theiss
Mean Looking Meso with Cone Tornado

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607. moonlightcowboy
8:03 PM CDT on May 23, 2008
First spin of the season, and impressive, too, I might add and especially for so early in the season.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
606. pottery
9:01 PM AST on May 23, 2008
Wow. Take cover Greensburg.
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605. bystander
12:58 AM GMT on May 24, 2008
567. StormW 11:55 PM GMT on May 23, 2008
558. rareaire 7:46 PM EDT on May 23, 2008
so what model do all of you weather big brains think is the best one this season.


It depends. I've seen each model during different seasons perform differently. The GFDL is usually pretty good with track...the GFS generally has feedback issues most of the time. We saw what the CMC did last season (near the end though, it was pretty right on). They had been doing some work on the HWRF, and supposedly it will be better than the GFDL. My personal preference would be the ECMWF, GFDL, and possibly the HWRF. The MM5 was so, so, but then again, I think it is a GFS based model, then again, thinking further, it's the WAVEWATCH model, not the MM5 that is run off the GFS. NOGAPS did lousy last season. It depends too how accurate and how much information is put in.


220-221, whatever it takes
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604. pottery
8:52 PM AST on May 23, 2008
MLC, it would need to maintain its formation overnight, and up to noon. If it can do that, then I think so too.
Pretty well set, right now though. Also, an awful lot of unsettled weather behind it too, so if this one fizzes, there are more on the way.
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603. TerraNova
8:58 PM EDT on May 23, 2008
A tornado warning has been issued for Greensburg. About 200 knots of shear (give or take 20 due to high spectrum width) are interacting with this system at the higher levels. Let's hope this weakens.
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602. moonlightcowboy
7:50 PM CDT on May 23, 2008
Hey, Pottery, I'm with you on this one. Come early morning, if it's still hanging around like that, except for distance out, I see no reason why it shouldn't be declared 90L.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
601. pottery
8:39 PM AST on May 23, 2008
Good Evening all.
Some interesting stuff out in the Trop. East Atlantic.
Some turn noted?
A low forming?
Not a lot of dry air around?
No dust ?

Its May 23, and its still at 6-7 degrees north. But it would be interesting to see what this gets up to, in the next 12 hrs. or so.
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600. TerraNova
8:34 PM EDT on May 23, 2008
Large supercell approaching Greensburg. Very large ciruculation.

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599. Smyrick145
12:36 AM GMT on May 24, 2008
Nash,
I live right outside of Oklahoma City. I watched that tornado tear through the metropolitan area live. It was an amazing site. I chased the mile to mile and a half wide tornado until I reached Midwest City. Couldn't drive any further due to so much debri in the road. Amazing stuff.
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598. Patrap
7:32 PM CDT on May 23, 2008

SevereStudios Moderator Feed is Live!
Click Here to Launch the SevereStudios Moderated Feed Link
Member Since: July 3, 2005 Posts: 423 Comments: 128259
597. Patrap
7:27 PM CDT on May 23, 2008
Member Since: July 3, 2005 Posts: 423 Comments: 128259
596. weathersp
8:22 PM EDT on May 23, 2008
Thanks Pat(Self Portrait?) and Adrian.
Member Since: January 14, 2007 Posts: 17 Comments: 4140
595. nash28
12:20 AM GMT on May 24, 2008
Just checking out old footage from the Moore, OK twister. Awesome. Awesome.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
594. hurricane23
8:18 PM EDT on May 23, 2008
591. weathersp 8:18 PM EDT on May 23, 2008
Can someone remind me of what the TUTT is again... I forgot from last year.. :(

Definition from Landsea...


A "TUTT" is a Tropical Upper Tropospheric Trough. A TUTT low is a TUTT
that has completely cut-off. TUTT lows are more commonly known in the
Western Hemisphere as an "upper cold low". TUTTs are different than mid-
latitude troughs in that they are maintained by subsidence warming near the
tropopause which balances radiational cooling. TUTTs are important for
tropical cyclone forecasting as they can force large amounts of harmful
vertical wind shear over tropical disturbances and tropical cyclones. There
are also suggestions that TUTTs can assist tropical cyclone genesis and
intensification by providing additional forced ascent near the storm center
and/or by allowing for an efficient outflow channel in the upper troposphere.

MORE HERE
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593. Patrap
7:11 PM CDT on May 23, 2008


tropical upper tropospheric trough, or TUTT (meteorology) Link

More in depth here Link
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592. moonlightcowboy
7:14 PM CDT on May 23, 2008
- Pat, LOL. All good links though!

- Adrian, yeah, totally agree. But, too, it is the only thing out there now that does look tropical. Low embedded in a twave, rotation, moving more west and north, convection persisting...except for its location, after 24 hours should, could be designated 90L imo - whether it dissipates or treks out to sea behind the TUTT.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
591. weathersp
8:17 PM EDT on May 23, 2008
Can someone remind me of what the TUTT is again... I forgot from last year.. :(
Member Since: January 14, 2007 Posts: 17 Comments: 4140
590. weathersp
8:12 PM EDT on May 23, 2008
Looks like one? I think it is!
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589. Patrap
7:12 PM CDT on May 23, 2008
Im dizzy and a-skeered of heights now
Member Since: July 3, 2005 Posts: 423 Comments: 128259
588. hurricane23
8:10 PM EDT on May 23, 2008
585. moonlightcowboy 8:10 PM EDT on May 23, 2008
Handsome rotation, but will it trek westward or get sucked in behind the TUTT?

Looks to me like its already being sucked up into the TUTT.Either way its enviroment ahead of it was not the greatest for tc development which comes as no suprise in may.
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587. nash28
11:53 PM GMT on May 23, 2008
That looks like a wedge tornado.
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586. hurricane23
8:09 PM EDT on May 23, 2008
1 more from EUMETSAT for viewing eastern atlantic.
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585. moonlightcowboy
7:09 PM CDT on May 23, 2008
Handsome rotation, but will it trek westward or get sucked in behind the TUTT?
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584. Patrap
7:08 PM CDT on May 23, 2008
Meteosat Image Link

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582. hurricane23
8:06 PM EDT on May 23, 2008
And of course you have your METEOSAT from SSD.
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581. hurricane23
8:04 PM EDT on May 23, 2008
577. weathersp 8:02 PM EDT on May 23, 2008
much better MLC.. :D

HERE is another great loop i use all the time for viewing the eastern atlantic.Ability to animate 8-18-24 frames.
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580. cchsweatherman
8:00 PM EDT on May 23, 2008
A WELL DEFINED TROPICAL WAVE IS ALONG 28W S OF 12N MOVING W
10-15 KT. A 1010 MB LOW IS NEAR 7N28W ALONG THE WAVE AXIS.
PRONOUNCED LOW-LEVEL TURNING IS APPARENT ON SATELLITE IMAGERY
AND GFS MODEL GUIDANCE SHOWS LOW-MID LEVEL CYCLONIC CURVATURE
WHICH IS HELPING TO ENHANCE SCATTERED SHOWERS AND ISOLATED TSTMS
CONFINED TO AN AREA N OF THE LOW CENTER FROM 8N-10N BETWEEN
26W-30W.
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579. weathersp
8:03 PM EDT on May 23, 2008
It's wierd that 2 areas of low pressure form. One goes through the panama area the dissapates around Jamica while another one is working its way through mexico and thats the one that the GFS has hitting FL.
Member Since: January 14, 2007 Posts: 17 Comments: 4140
577. weathersp
8:02 PM EDT on May 23, 2008
much better MLC.. :D
Member Since: January 14, 2007 Posts: 17 Comments: 4140
576. rareaire
11:58 PM GMT on May 23, 2008
thanks hurricane and storm. I appreciate the help. I have to be in tahlahasse in a week for training and I dont want any surprises.
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575. moonlightcowboy
7:00 PM CDT on May 23, 2008
Try it again, sp! LOOP

Location appears to be about 8n, 29w.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
574. hurricane23
8:00 PM EDT on May 23, 2008
569. jphurricane2006 7:57 PM EDT on May 23, 2008
where do you see the 18Z NOGAPS Adrian?

My bad buddy HERE you go it trys to close a low at around 1008-1009mb in the sw caribbean.18z.
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573. Patrap
6:59 PM CDT on May 23, 2008
Verifying Output,the MM5Link
Member Since: July 3, 2005 Posts: 423 Comments: 128259
572. weathersp
7:57 PM EDT on May 23, 2008
Hey HLC you have 2 Http//: in that link..
Member Since: January 14, 2007 Posts: 17 Comments: 4140
571. Patrap
6:58 PM CDT on May 23, 2008
MM5 Community Model Homepage Link
Member Since: July 3, 2005 Posts: 423 Comments: 128259
568. moonlightcowboy
6:56 PM CDT on May 23, 2008
StormW, it looks like it's gonna make it thru under the TUTT as well. Thoughts?
Member Since: July 9, 2006 Posts: 184 Comments: 29610
566. moonlightcowboy
6:54 PM CDT on May 23, 2008
EATL rotation fairly impressive imo. LOOP
Member Since: July 9, 2006 Posts: 184 Comments: 29610
565. InTheCone
7:48 PM EDT on May 23, 2008
Been Doing some super lurking, reading all of your excellent prognostications, seeing the recent GFS forecasts and even seeing some VERY early waves off Africa. I don't know 'nothin, but it sure looks like this is going to be a VERY interesting season.

God Bless us all, as ANY interruption in fossil fuel production will only add to everyone's pain at the pump :(
Member Since: September 1, 2007 Posts: 0 Comments: 1979
564. hurricane23
7:52 PM EDT on May 23, 2008
563. rareaire 7:50 PM EDT on May 23, 2008
Storm lst season you posted a link to a web page that had numerous models run siimultaneously. Can you please re post it for me. I got a new laptop this year and I dont have a lot of the great links you guys posted on here ....

VIEW HERE
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563. rareaire
11:48 PM GMT on May 23, 2008
Storm lst season you posted a link to a web page that had numerous models run siimultaneously. Can you please re post it for me. I got a new laptop this year and I dont have a lot of the great links you guys posted on here ....
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562. weathersp
7:46 PM EDT on May 23, 2008
By the pictures of the damage I saw from the windsor tornado I thought it might of been a EF4 or a High End EF3. But a EF2-EF3 thats interesting.
Member Since: January 14, 2007 Posts: 17 Comments: 4140
561. hurricane23
7:47 PM EDT on May 23, 2008
Raw video of *huge* tornado in Colorado

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558. rareaire
11:45 PM GMT on May 23, 2008
so what model do all of you weather big brains think is the best one this season.
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557. weathersp
7:41 PM EDT on May 23, 2008
555. How'd you know :0
Member Since: January 14, 2007 Posts: 17 Comments: 4140

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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.