Dr. Jeff Masters' WunderBlog

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

Posted by: Dr. Jeff Masters, 13:23 GMT le 23 mai 2008

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

Tornado Damage 3 (jlg)

Damage from today's Tornado in Windsor, Colorado

()

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

Categories: Tornado

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551. charley11 23:37 GMT le 23 mai 2008
the gfs dropped the storm? ah, thought so. but you know, it might pick back up on it in the next couple runs. Regardless, this episode should serve as a wake-up call that the Tropical Atlantic has now PASSED the point where cyclonic formation is no longer unlikely. On that note, I've got a bad feeling about that little spin lurking out in the distance by Africa. The implications of the presence of a tropical LOW in MAY scare me more than anything I've seen lately.

552. hurricane23 23:38 GMT le 23 mai 2008
Might want to and the 18z nogaps to that pack JP. Member Since: 14 mai 2006 Posts: 8 Comments: 13331

553. weathersp 23:39 GMT le 23 mai 2008
550. jphurricane2006 7:37 PM EDT on May 23, 2008 sp and jp? hey are we related? we have the same last um letter LOL Freaky Dude.. Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

554. charley11 23:39 GMT le 23 mai 2008
also, there's a decent chance the models' predicted storm in the pacific will come to fruition.

556. weathersp 23:41 GMT le 23 mai 2008
552. Not as much.. but it does take a turn NE through 228 hrs. Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

557. weathersp 23:43 GMT le 23 mai 2008
555. How'd you know :0 Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

558. rareaire 23:46 GMT le 23 mai 2008
so what model do all of you weather big brains think is the best one this season. Member Since: 19 août 2007 Posts: 0 Comments: 1598

561. hurricane23 23:48 GMT le 23 mai 2008
Raw video of huge tornado in Colorado Member Since: 14 mai 2006 Posts: 8 Comments: 13331

562. weathersp 23:49 GMT le 23 mai 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: 14 janvier 2007 Posts: 17 Comments: 4112

563. rareaire 23:50 GMT le 23 mai 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 .... Member Since: 19 août 2007 Posts: 0 Comments: 1598

564. hurricane23 23:53 GMT le 23 mai 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 Member Since: 14 mai 2006 Posts: 8 Comments: 13331

565. InTheCone 23:54 GMT le 23 mai 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: 1 septembre 2007 Posts: 0 Comments: 1979

566. moonlightcowboy 23:55 GMT le 23 mai 2008
EATL rotation fairly impressive imo. LOOP Member Since: 9 juillet 2006 Posts: 179 Comments: 28212

568. moonlightcowboy 23:57 GMT le 23 mai 2008
StormW, it looks like it's gonna make it thru under the TUTT as well. Thoughts? Member Since: 9 juillet 2006 Posts: 179 Comments: 28212

571. Patrap 23:59 GMT le 23 mai 2008
MM5 Community Model Homepage Link Member Since: 3 juillet 2005 Posts: 377 Comments: 113014

572. weathersp 23:59 GMT le 23 mai 2008
Hey HLC you have 2 Http//: in that link.. Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

573. Patrap 00:00 GMT le 24 mai 2008
Verifying Output,the MM5Link Member Since: 3 juillet 2005 Posts: 377 Comments: 113014

574. hurricane23 00:01 GMT le 24 mai 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. Member Since: 14 mai 2006 Posts: 8 Comments: 13331

575. moonlightcowboy 00:01 GMT le 24 mai 2008
Try it again, sp! LOOP Location appears to be about 8n, 29w. Member Since: 9 juillet 2006 Posts: 179 Comments: 28212

576. rareaire 00:02 GMT le 24 mai 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. Member Since: 19 août 2007 Posts: 0 Comments: 1598

577. weathersp 00:02 GMT le 24 mai 2008
much better MLC.. :D Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

579. weathersp 00:05 GMT le 24 mai 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: 14 janvier 2007 Posts: 17 Comments: 4112

580. cchsweatherman 00:05 GMT le 24 mai 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. Member Since: 14 avril 2007 Posts: 8 Comments: 4928

581. hurricane23 00:05 GMT le 24 mai 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. Member Since: 14 mai 2006 Posts: 8 Comments: 13331

582. hurricane23 00:07 GMT le 24 mai 2008
And of course you have your METEOSAT from SSD. Member Since: 14 mai 2006 Posts: 8 Comments: 13331

584. Patrap 00:09 GMT le 24 mai 2008
Meteosat Image Link Member Since: 3 juillet 2005 Posts: 377 Comments: 113014

585. moonlightcowboy 00:10 GMT le 24 mai 2008
Handsome rotation, but will it trek westward or get sucked in behind the TUTT? Member Since: 9 juillet 2006 Posts: 179 Comments: 28212

586. hurricane23 00:10 GMT le 24 mai 2008
1 more from EUMETSAT for viewing eastern atlantic. Member Since: 14 mai 2006 Posts: 8 Comments: 13331

587. nash28 00:10 GMT le 24 mai 2008
That looks like a wedge tornado. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

588. hurricane23 00:12 GMT le 24 mai 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. Member Since: 14 mai 2006 Posts: 8 Comments: 13331

589. Patrap 00:13 GMT le 24 mai 2008
Im dizzy and a-skeered of heights now Member Since: 3 juillet 2005 Posts: 377 Comments: 113014

590. weathersp 00:15 GMT le 24 mai 2008
Looks like one? I think it is! Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

591. weathersp 00:18 GMT le 24 mai 2008
Can someone remind me of what the TUTT is again... I forgot from last year.. :( Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

592. moonlightcowboy 00:20 GMT le 24 mai 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: 9 juillet 2006 Posts: 179 Comments: 28212

593. Patrap 00:20 GMT le 24 mai 2008
tropical upper tropospheric trough, or TUTT (meteorology) Link More in depth here Link Member Since: 3 juillet 2005 Posts: 377 Comments: 113014

594. hurricane23 00:20 GMT le 24 mai 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 Member Since: 14 mai 2006 Posts: 8 Comments: 13331

595. nash28 00:21 GMT le 24 mai 2008
Just checking out old footage from the Moore, OK twister. Awesome. Awesome. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

596. weathersp 00:25 GMT le 24 mai 2008
Thanks Pat(Self Portrait?) and Adrian. Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

597. Patrap 00:27 GMT le 24 mai 2008
Member Since: 3 juillet 2005 Posts: 377 Comments: 113014

598. Patrap 00:32 GMT le 24 mai 2008
SevereStudios Moderator Feed is Live! Click Here to Launch the SevereStudios Moderated Feed Link Member Since: 3 juillet 2005 Posts: 377 Comments: 113014

599. Smyrick145 00:38 GMT le 24 mai 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. Member Since: 30 septembre 2006 Posts: 0 Comments: 14

600. TerraNova 00:38 GMT le 24 mai 2008
Large supercell approaching Greensburg. Very large ciruculation. Member Since: 30 juillet 2007 Posts: 76 Comments: 4058

601. pottery 00:48 GMT le 24 mai 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. Member Since: 24 octobre 2005 Posts: 0 Comments: 20866

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