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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457. Weather456
6:01 PM AST on May 23, 2008
Lastest image of the tropical wave out there:

Member Since: July 24, 2005 Posts: 407 Comments: 19076
456. IKE
5:10 PM CDT on May 23, 2008
he-he....mud wrestling...that does make sense...ECMWF forever etched in the mind as a wrestling federation.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
455. cchsweatherman
6:07 PM EDT on May 23, 2008
454. pearlandaggie 6:07 PM EDT on May 23, 2008
I think it should be
Extreme Championship Mud Wrestling Federation!

LOL


Nice one! How come I couldn't think of that? (Hits head on desk lightly as not to inflict pain for no reason.) LOL
Member Since: April 14, 2007 Posts: 8 Comments: 5169
454. pearlandaggie
10:05 PM GMT on May 23, 2008
I think it should be
Extreme Championship Mud Wrestling Federation!

LOL
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453. HurricaneGeek
5:58 PM EDT on May 23, 2008
Extreme
Competitors
for the
Men's
Wrestling
Foundation

It's a foundation for the best non-pro wrestles. They have meeting and dinners. It's like a bonding club.
LOL- I just made that up off the top of my head.
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452. cchsweatherman
6:03 PM EDT on May 23, 2008
450. StormJunkie 6:02 PM EDT on May 23, 2008
Mixed

Is that a racial slur? or are we talking co-ed :~)


Why would you even think that would be a racial slur? If you watch TNA Wrestling at all, there is a 6'7", 298lb. female wrestler named Awesome Kong who has now started wrestling the male wrestlers there. Anyways, that's the only word that started with "M" that I thought fit in. LOL.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
451. Patrap
5:03 PM CDT on May 23, 2008
Thanx for the Kudos, To be sure cchs,most know Im ready 365.

Flags In
23 May 2008
More than 3,000 soldiers, sailors, airmen and Marines officially kicked off Memorial Day commemoration, by placing 265,000 flags at Arlington National Cemetery, May 22, 2008

Video Courtesy Defenselink:Link

Member Since: July 3, 2005 Posts: 426 Comments: 128617
450. StormJunkie
10:01 PM GMT on May 23, 2008
446

Mixed

Is that a racial slur? or are we talking co-ed :~)
Member Since: August 17, 2005 Posts: 26 Comments: 16827
449. cchsweatherman
6:00 PM EDT on May 23, 2008
Patrap,

Wish you and your family a great Memorial Day weekend. Keep up the great work and hope you will be ready for hurricane season to begin.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
448. StormJunkie
9:59 PM GMT on May 23, 2008
Pat 2 days til we touch down on the N pole.....of Mars :~)

Is there going to be a live feed from inside JPL or Nasa? I'll bite my nails right along with those folks during blackout if I can watch it or listen in!
Member Since: August 17, 2005 Posts: 26 Comments: 16827
447. seflagamma
5:59 PM EDT on May 23, 2008
LOL! SJ!!! too funny.

I saw StormW in here while ago also.

got a few more things to do here at work so probably gone for the night.

have a good evening everyone!
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446. cchsweatherman
5:58 PM EDT on May 23, 2008
438. pearlandaggie 5:52 PM EDT on May 23, 2008
I still think the ECMWF sounds like a professional wrestling outfit! :)


Extreme Championship Mixed Wrestling Federation

Member Since: April 14, 2007 Posts: 8 Comments: 5169
445. Patrap
4:58 PM CDT on May 23, 2008
Have a Safe and Happy Memorial Day Weekend Everyone.

U.S.S. KEARSARGE PASSES LADY LIBERTY

The amphibious assault ship USS Kearsarge passes by the Statue of Liberty as it steams up the Hudson River during the Parade of Ships for Fleet Week New York, May 21, 2008. More than 4,000 sailors, Marines, and Coast Guardsmen will participate in various community relations projects and make a port call to New York City.Link

U.S. Navy photo by Petty Officer 3rd Class David Danals
Member Since: July 3, 2005 Posts: 426 Comments: 128617
444. Weather456
5:52 PM AST on May 23, 2008
419. cchsweatherman 5:35 PM AST on May 23, 2008

Well from what I see ur right...but it also tells us we have some model consensus...which i have been looking for.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
443. cchsweatherman
5:52 PM EDT on May 23, 2008
436. kingy 5:50 PM EDT on May 23, 2008
CCHSweatherman, thank you for your intelligent and well written insights. I always appreciate your comments. You are one of the emerging young talents in the science of weather and I am sure you are a solid citizen as well. keep up the good work son.


Thank you very much. It is my pleasure and my self-imposed duty to make sure everyone is at least prepared and forewarn on any possible weather. This has been a burning passion for the past eight years (and I'm only 18) and will continue to burn inside me until I die. Comments like that means so much to me and just add even more motivation for me to continue doing what I'm doing. From that comment, you must be a solid citizen yourself. I look forward to hearing more from you throughout hurricane season and thanks again for the praise.

Member Since: April 14, 2007 Posts: 8 Comments: 5169
441. StormJunkie
9:50 PM GMT on May 23, 2008
Yep Gamma, it did. Many of the beaches N of Wilmington also have a huge drop. But I think one part of what makes the surge seem so different in these areas, is not the shelf in the water, but the fact that the inland areas also tend to elevate more quickly in areas with out a shelf as opposed to with a shelf. So technically you could have the exact same surge from sea level and yet it would seem or appear worse in areas that had a very gradual slope up from sea level. Basically exactly what you said, but I am looking more at the land areas as being one of the big factors as opposed to the shelf itself. Granted I think the two are interconnected.

If that makes any sense! Don't worry Gams, I am sure we can sufficiently confuse each other if we keep trying :~))
Member Since: August 17, 2005 Posts: 26 Comments: 16827
439. IKE
4:53 PM CDT on May 23, 2008
lol.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
438. pearlandaggie
9:51 PM GMT on May 23, 2008
I still think the ECMWF sounds like a professional wrestling outfit! :)
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437. pearlandaggie
9:49 PM GMT on May 23, 2008
SJ, nope. Born and raised in Texas. However, even from an early age I was fascinated by hurricanes. I remember Gilbert, Hugo, and Andrew almost like it was yesterday.
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436. kingy
9:47 PM GMT on May 23, 2008
CCHSweatherman, thank you for your intelligent and well written insights. I always appreciate your comments. You are one of the emerging young talents in the science of weather and I am sure you are a solid citizen as well. keep up the good work son.
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434. pearlandaggie
9:48 PM GMT on May 23, 2008
430. Mike, that's really interesting. I didn't realize the EPac normally had such a low TCHP. Thanks for sharing that!
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433. seflagamma
5:43 PM EDT on May 23, 2008
HI SJ, yes you are right, down here in SE Fla, we don't have to go far off the beach to be in deep water..where the gulf it seems you can walk out for a mile and still be waist deep; it is just not as deep out there...isn't the North EAST Fla the same way, longer beach shelfs? I think that is why we did not have a worse storm surge with Andrew in 92.. I know it was high, I think 18" but I think that was only in Key Byscayne and that area has a long beach area.

I just don't see Ft Lauderdale having a 25- 30ft storm surge with the way our shelf is positioned..

Did any of that make sense?
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432. StormJunkie
9:48 PM GMT on May 23, 2008
Not quite yet Aggie, but getting there faster then I would like!

Were you in the Charleston area?
Member Since: August 17, 2005 Posts: 26 Comments: 16827
431. pearlandaggie
9:47 PM GMT on May 23, 2008
SJ, you're an OLD man :)

I was 13 when that happened! :)
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429. StormJunkie
9:45 PM GMT on May 23, 2008
Yep Aggie, If you could zoom in on that image you would see me in the clear area at the young age of 17 looking up and being amazed at the calm and beauty of the night sky....Then came another six hours of hell.
Member Since: August 17, 2005 Posts: 26 Comments: 16827
428. pearlandaggie
9:43 PM GMT on May 23, 2008
Hugo...did someone say Hugo?

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427. StormJunkie
9:39 PM GMT on May 23, 2008
Good TN and yourself?

Also back to that "the surge is larger in the Gulf" deal. Last time we had this discussion and referenced Hugo where there was at least a 20 foot surge. Some one had stated that surges are 3 to 4 time bigger in the Gulf then on the E coast and I disputed that Hugo would not have had a 60' surge no matter where it landed.

That said, the real issue here is the shelf right, not Gulf vs E coast? Basically there is a shelf from Jax to Wilmington? Where as the OBX and S Fla do not have a shelf?
Member Since: August 17, 2005 Posts: 26 Comments: 16827
426. TerraNova
5:39 PM EDT on May 23, 2008
It just began to show development there today. Give it some more runs before you judge consistency.

I think it showed something during yesterday's 06z run (I posted about it yesterday) but yes, you're right.
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425. pearlandaggie
9:36 PM GMT on May 23, 2008
417. with a TCHP distribution like that, no Wonder NOAA is predicting a below average EPac storm season.
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424. cchsweatherman
5:38 PM EDT on May 23, 2008
421. TerraNova 5:38 PM EDT on May 23, 2008
Interestingly, the NAM now shows a potential development in the SW Caribbean. At least the GFS isn't alone now; but the NAM has shown little to no run to run consistency so far.


It just began to show development there today. Give it some more runs before you judge consistency.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
423. TerraNova
5:38 PM EDT on May 23, 2008
Afternoon SJ; how's everything going?
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422. cchsweatherman
5:35 PM EDT on May 23, 2008
Just to let you all know, my visit to the NHC has been rescheduled for June 13th as the meteorologist I was scheduled to meet with had to cancel on me. I have asked and I will be permitted to take pictures at the NHC, so after my visit there, I will have a blog describing my experience and with pictures there. Maybe I'll meet Bill Read there?!
Member Since: April 14, 2007 Posts: 8 Comments: 5169
421. TerraNova
5:29 PM EDT on May 23, 2008
Interestingly, the NAM now shows a potential development in the SW Caribbean. At least the GFS isn't alone now; but the NAM has shown little to no run to run consistency so far.
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420. StormJunkie
9:29 PM GMT on May 23, 2008
416. lol

Back to the shelf. I was just kicked back in the recliner dozing and thinking, which tends to happen the most when I am trying to nap. Could the larger surge associated with areas that have a shelf be a perception issue as well. I know it is not the only issue, but it would seem that most times where there is a shelf the landmass would also slope more gradually then in areas without a shelf. Example Miami. I have only been once, but it seemed to me that when you got 30 yards off the beach you were already up off water level 10 to 20 feet. Where as along a shelf 30 yards in may only gain you a few feet, hence the same size surge in both areas would actually be perceived as larger where there is a more gradual slope because the water would be allowed to travel further inland at a higher level?

Next I was wondering what the typical tides are like in the Gulf, and how they vary from the typical tides along the E coast?
Member Since: August 17, 2005 Posts: 26 Comments: 16827
419. cchsweatherman
5:31 PM EDT on May 23, 2008
Hey 456, Storm, Drak, or anybody else,

Have you seen the latest 18UTC NAM model? At 84 hours out, the model shows tropical development (albeit somewhat broad low) occuring the Southwest Caribbean and a tropical storm forming in the Eastern Pacific. It seems like the NAM starts moving the Eastern Pacific system westward, thus allowing the Southwest Caribbean system to begin forming. Thoughts on this? This may be some support for the GFS model.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
418. IKE
4:34 PM CDT on May 23, 2008
It's running now.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
417. Drakoen
9:28 PM GMT on May 23, 2008
I'm waiting for the GFS 18z run. That 12z run what the first run in the last few days that showed significant tropical cyclone development in the EPAC. Most of the runs have been exploding the Caribbean system. I'm also wondering where the intensification is going to come from with the significant lack of tropical cyclone heat potential in the EPAC.
Member Since: October 28, 2006 Posts: 57 Comments: 30559
416. atmoaggie
9:26 PM GMT on May 23, 2008
Who's talking about who's mom ¿~)

That was a methaphor. Didn't really have a brawl either. We should probably leave it at that our we will likely have another.
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415. surfmom
9:27 PM GMT on May 23, 2008
off to be domestic - grrrr
Member Since: July 18, 2007 Posts: 30 Comments: 26536
414. Drakoen
9:26 PM GMT on May 23, 2008
412. StormW 9:26 PM GMT on May 23, 2008
Drak...post 394...also noticed the warm water starting to show off South America west coast.


Yea.
Member Since: October 28, 2006 Posts: 57 Comments: 30559
413. Weather456
5:23 PM AST on May 23, 2008
397. KarenRei 5:08 PM AST on May 23, 2008

It was mentioned earlier....not likely the one the GFS has been forecasting.


Also QuikSCAT appears to missed the low in the EATL
Member Since: July 24, 2005 Posts: 407 Comments: 19076
411. IKE
4:26 PM CDT on May 23, 2008
Yo bud.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
410. surfmom
9:24 PM GMT on May 23, 2008
seflagamma - thanks a terrific radar!
Member Since: July 18, 2007 Posts: 30 Comments: 26536
409. seflagamma
5:23 PM EDT on May 23, 2008
you are welcome Ike, by the way, it's Gams or Gamma... my handle is way too long, didn't realize what I was doing back in summer of 2005 when I picked it! LOL
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408. surfmom
9:22 PM GMT on May 23, 2008
Re:tadpoles/ Oh yes, try to be sure the tap water has been left out for a while to evaporate out the cholrine
Member Since: July 18, 2007 Posts: 30 Comments: 26536
407. IKE
4:22 PM CDT on May 23, 2008
It's fixing to rain here...thanks for posting that seflgamma! I didn't know it......lol.
Member Since: June 9, 2005 Posts: 23 Comments: 37858

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.