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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1406. TerraNova
8:51 PM EDT on May 24, 2008
why does it seem everytime i post i KILL the blog activity? :)

LOL I'm sure it's not your fault :D
Member Since: July 30, 2007 Posts: 76 Comments: 4063
1405. lopaka001
8:45 PM EDT on May 24, 2008
Nice pics hurricane23!
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1404. pearlandaggie
12:50 AM GMT on May 25, 2008
why does it seem everytime i post i KILL the blog activity? :)
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1402. TerraNova
8:44 PM EDT on May 24, 2008
Interesting...the GFS has fallen into very close agreement with the ECMWF. It also shows the Atlantic storm absorbing the Pacific storm, although how likely this is, I don't know.
Member Since: July 30, 2007 Posts: 76 Comments: 4063
1401. pearlandaggie
12:41 AM GMT on May 25, 2008


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1400. InTheCone
8:41 PM EDT on May 24, 2008
But dang it all, ptrapper, yourse links is sure darnred interestin'....
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1398. Patrap
7:36 PM CDT on May 24, 2008
Hurricane Preparedness Week

Be Ready,Be Prepared ,..have a Plan.
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1396. hurricane23
8:31 PM EDT on May 24, 2008
Thanks sngalla...

Those light poles really kill the pics.
Member Since: May 14, 2006 Posts: 8 Comments: 13804
1395. sngalla
8:29 PM EDT on May 24, 2008
I saw that, lopaka001!

Nice shots, Adrian!
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1394. hurricane23
8:29 PM EDT on May 24, 2008
Few pics from severe storm over the house in miami!



Member Since: May 14, 2006 Posts: 8 Comments: 13804
1393. Patrap
7:22 PM CDT on May 24, 2008
Updated Disaster Page

ReliefWEB Link
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1392. lopaka001
8:21 PM EDT on May 24, 2008
Looks like round 3 is coming down the pipe!
595 and 441 going to get hit again here shortly
Sngalla!
Link
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1390. sngalla
8:17 PM EDT on May 24, 2008
I hear you!
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1389. Patrap
7:15 PM CDT on May 24, 2008
An EF-0 can kill and do damage to Property as easily as the EF-5.
Situations are always fluid.
Never risk life or Limb to see.
It aint worth it.
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1388. lopaka001
8:16 PM EDT on May 24, 2008
Lol my buddy just went to Cancun yesterday and now looking at the radar image SW
of Cancun there is some serious storms brewing up.
Geez that is some big time rain I wonder
what the altitude is of that storm top.
Link
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1387. Michfan
7:13 PM CDT on May 24, 2008
Im just going to report the living hell out of people that dont' stay focused this year on the topics at hand. Last year was terrible enough. Not everyone is right. Meteorology isn't an exact science and is therefore up to interpretation.
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1386. sngalla
8:14 PM EDT on May 24, 2008
Patrap, the ones here are usually harmless.
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1385. Patrap
7:13 PM CDT on May 24, 2008
Severe Warnings Page Link
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1384. Patrap
7:11 PM CDT on May 24, 2008
I wouldnt be too,disappointed, Meeting one up close isnt the best day,for most
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1383. sngalla
8:09 PM EDT on May 24, 2008
Darn! I missed seeing the funnel cloud!
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1382. hahaguy
8:07 PM EDT on May 24, 2008
wow we just got a nasty storm here. We got the works.
Member Since: August 12, 2007 Posts: 2 Comments: 2838
1381. Patrap
6:59 PM CDT on May 24, 2008
MODIS image from the 21 May Short Wave that traversed the GOM and brought a Lot of rainLink
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1380. lopaka001
8:01 PM EDT on May 24, 2008
Thanks Sngalla!
You see that funnel cloud it travel south from 595 and ran parallel to 441 on the west side.
Looks like the hard Rock Casino diffuse it.
My neighbors wind gauge said 32mph on the reading at the time of that last cell but not sure how accurate it is.
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1379. surfmom
12:05 AM GMT on May 25, 2008
signing off, teenage boys in house - raucous and rowdy = looks like I'm on teen patrol! G'nite all
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1378. surfmom
12:02 AM GMT on May 25, 2008
patrap - a master of diversion!LOL. hope the boys stop slinging testosterone.
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1377. Patrap
7:03 PM CDT on May 24, 2008
ESL image of the Week Link
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1375. Patrap
7:00 PM CDT on May 24, 2008
Tease,who me? "Snicker,grunt,giggle,snort".
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1374. surfmom
11:57 PM GMT on May 24, 2008
patrap why the OmG re: your link - sorry not too sure what I am looking at LOL can't tell if your teasing or serious
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1372. Patrap
6:55 PM CDT on May 24, 2008
GOES-12 Low Cloud Product GOM Link
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1371. sngalla
7:55 PM EDT on May 24, 2008
Hi all!
lopaka001, we are located about a mile from 441 and 595. We got 2.32 inches of rain so far today.
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1370. msuwxman
6:56 PM CDT on May 24, 2008
1351. Wow that twister really has some cahones!!
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1369. moonlightcowboy
6:45 PM CDT on May 24, 2008
1360. Drak may be right about Dean in the initialization process, and he may have implied that, but that's not what he said. Hey, I like Drak - get along with him, smart dude, learn from him, ask him questions, always helpful; and, I'm not arguing with him now either. But, I can make a statement myself about models if I choose. First off, the models themselves are different. They're built different in that many interpret data for different reasons and purposefully will find different solutions, meaning that "congruence" isn't a real possibility anyway, not before, not at initialization, and not with track either. They're all different and will be different. They're may be some similarities, but they will all be different.

Vort's smart, too, no doubt and has a passion for severe weather and does a great job.

And, just like the models, we're all different, too. Many bring a great deal to the blog, in different ways. We can see elements of things at different times that others may miss, or add to the discussion. Ultimately, it's a nice place where all the knowledge comes together for discernment and understanding. That's what makes it good!

LOL, that's if we don't strangle each other first, or blow a fuse!
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1368. KEEPEROFTHEGATE (Mod)
7:53 PM EDT on May 24, 2008
hey jp BWRC.
lol
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1367. Patrap
6:54 PM CDT on May 24, 2008
GOES-12 Atmospheric Imagery ESL Link

OMG!!!!!!!!! Link
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1366. lopaka001
7:53 PM EDT on May 24, 2008
Hey MasterForecaster you got that right...
From severe drought to hail today and a nice size funnel cloud here at Davie 441 & 595 just 15mins ago.
I was watching the funnel cloud when lighting hit my neighbors pine tree..
My eye sockets are hurting and I almost soiled my shorts lol..
The rain is very heavy I wonder how many inches we are getting today?
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1365. Patrap
6:53 PM CDT on May 24, 2008
..Ask not,what the Blog can do for you,
But what you can do,..for the Blog
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1364. Weather456
7:43 PM AST on May 24, 2008
Well, vort is entitled to his opinion and frankly its not gonna change anything. I mean whose gonna stop talking about the tropics becuz someone wants them to. Not I. I mean i live in the heart of the tropics therefore i know little about severe weather and whats not so I stick to what I know and love.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1363. Drakoen
11:47 PM GMT on May 24, 2008
I like how people can go to their blogs and say what they want to say about me but can't say it to my face. I have zero tolerance this season for anyone. I look forward to adding people to my ignore list if need be. There are just too many egos around here.
Member Since: October 28, 2006 Posts: 57 Comments: 30559
1362. FLWeatherFreak91
7:45 PM EDT on May 24, 2008
1361:

Very true. We're all pretty strange people with a strange obsession. IMHO
Member Since: December 1, 2006 Posts: 2 Comments: 3623
1360. FLWeatherFreak91
7:43 PM EDT on May 24, 2008
Drak, I very much respect and follow your weather knowledge, but I don't "trust" any model. And, Dean was hardly 100 percent congruent. There was much talk about a Houston landfall, etc, with Dean.

I'm pretty sure drak was referring to the storm's initial genesis, not its final course.
Member Since: December 1, 2006 Posts: 2 Comments: 3623
1359. hurricane23
7:42 PM EDT on May 24, 2008
Hey ivan!

Watching this severe storm in north dade looks like it might clip me.NWS reporting winds in excess of 70mph.
Member Since: May 14, 2006 Posts: 8 Comments: 13804
1358. Ivansrvivr
11:40 PM GMT on May 24, 2008
Drak, looks like I may have to use my "easy button" again. I don't understand why someone comes on the tropical weather blog and gets upset because were talking tropics.
1357. Drakoen
11:41 PM GMT on May 24, 2008
1356. moonlightcowboy 11:40 PM GMT on May 24, 2008
Drak, I very much respect and follow your weather knowledge, but I don't "trust" any model. And, Dean was hardly 100 percent congruent. There was much talk about a Houston landfall, etc, with Dean.



I meant with initial development of the coast of Africa not track.
Member Since: October 28, 2006 Posts: 57 Comments: 30559

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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.