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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2007. Stormchaser2007
10:55 PM GMT on May 25, 2008
Drak, Never mind it was stupid of me to try and ask something personal like that. Im sorry....
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2006. weathersp
6:50 PM EDT on May 25, 2008
Intresting that the 12z GFS and now the 18z GFS now agree with the NOGAPS..
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2004. nash28
10:57 PM GMT on May 25, 2008
Actually Ike, probably not..

Why??? The early track runs are usually 100's of miles off:-)

Trust me, I've learned that lesson plenty here:-)
Member Since: July 11, 2005 Posts: 190 Comments: 16972
2003. JLPR
6:57 PM AST on Mayo 25, 2008
I see there isn't anything new in the tropics but apparently the models want to develop something right on the start of the season we will just have to wait and see =)
and Hello everyone =)
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2002. IKE
5:58 PM CDT on May 25, 2008
lol.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
2001. stormhank
10:55 PM GMT on May 25, 2008
Hey Drak n SJ.. I just got home from work...whats latest on potential GFS system??
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2000. IKE
5:56 PM CDT on May 25, 2008
It heads north into the Florida panhandle....
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1999. nash28
10:55 PM GMT on May 25, 2008
Not that it isn't possible, but the GFS is trying to pull an Elena circa 1985.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1998. nash28
10:54 PM GMT on May 25, 2008
Stalls too long.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1997. moonlightcowboy
5:53 PM CDT on May 25, 2008
I wonder just how big that front-end loader is on the landing craft? Does the name "Caterpillar" need to go on the side of it, or is it more like a shovel for a beach pail?
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1996. nash28
10:53 PM GMT on May 25, 2008
I see "Michael" is the meteorologist among us tonight..
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1995. Patrap
5:53 PM CDT on May 25, 2008
3:35 pm PDT NASA Blog Link
It's great to see so many people following along in the comments. We are currently receiving real-time data from the spacecraft via the Deep Space Network. In fact, we had near continuous coverage for the last couple weeks in order to keep a careful eye on the spacecraft status. Some of you may notice from the live shot on NASA TV a green and black chart on the wall. This chart shows our Doppler shift as a result of the increase in speed of our spacecraft due to the Mars "gravity well." As get closer and closer to Mars, we pick up speed due to gravity. We enter the atmosphere at over 12,000 miles per hour, relative to Mars. We are now about an hour from EDL. 3:15 pm
We've just completed the 90-minute (from EDL) poll, verifying that the Mars Odyssey orbiter, Mars Reconaissance Orbiter, and Mars Express are "go" for EDL communications support. While Mars Odyssey relays data back to Earth during EDL, Mars Reconaissance Orbiter will play back data later.
Member Since: July 3, 2005 Posts: 414 Comments: 125466
1994. Stormchaser2007
10:51 PM GMT on May 25, 2008
Oh no reason just wanted to know out of pure curiosity??
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1993. Drakoen
10:52 PM GMT on May 25, 2008
1991. nash28 10:52 PM GMT on May 25, 2008
18z GFS still drunk.


Doesn't look too drunk to me. At least its not showing a big high and showing some affect with that trough.
Member Since: October 28, 2006 Posts: 57 Comments: 29714
1992. presslord
6:51 PM EDT on May 25, 2008
sj...Why not question them? You act like they're a bunch of rocket scientists or something....
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1991. nash28
10:50 PM GMT on May 25, 2008
18z GFS still drunk.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1990. StormJunkie
10:50 PM GMT on May 25, 2008
1981.

Thanks press, makes sense. And for the record, I was not really questioning these guys. Just wondering why.
Member Since: August 17, 2005 Posts: 26 Comments: 15472
1989. Drakoen
10:50 PM GMT on May 25, 2008
1987. IKE 10:50 PM GMT on May 25, 2008
Thank God for the ignore option!


Yea lol!
Member Since: October 28, 2006 Posts: 57 Comments: 29714
1988. Drakoen
10:50 PM GMT on May 25, 2008
1986. Stormchaser2007 10:50 PM GMT on May 25, 2008
Drak just a question where are you located??


Why?
Member Since: October 28, 2006 Posts: 57 Comments: 29714
1987. IKE
5:49 PM CDT on May 25, 2008
Thank God for the ignore option!
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1986. Stormchaser2007
10:49 PM GMT on May 25, 2008
Drak just a question where are you located??
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1985. presslord
6:47 PM EDT on May 25, 2008
OMG.....Pat was right ...Pensacola is doomed....
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1984. kingy
10:33 PM GMT on May 25, 2008
I know there are a lot of folk keen to see tropical storm season starting....but remember some of these storms are killers. The rest cost us billions as a nation. My former construction company lost nearly a quarter million in un-insured losses during Andrew. After that I bought the insurance. I have a modest house in the florida keys, and that costs me around $17,000 every year in insurance alone.
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1983. Stormchaser2007
10:46 PM GMT on May 25, 2008
Also the GFS has something off of Arfica in 120-144 hours I think.
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1981. presslord
6:44 PM EDT on May 25, 2008
sj...this thing is too big for the bouncy ball landing...
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1980. Drakoen
10:46 PM GMT on May 25, 2008
Looks like I have a new addition to my ignore list. Haven't had one in about 7-8 months.
Member Since: October 28, 2006 Posts: 57 Comments: 29714
1979. IKE
5:45 PM CDT on May 25, 2008
That seems more in line w/June tracks.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1977. Stormchaser2007
10:42 PM GMT on May 25, 2008
DELETED
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1976. IKE
5:43 PM CDT on May 25, 2008
Brings it in in the Florida panhandle.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1974. Drakoen
10:42 PM GMT on May 25, 2008
The GFS claims Tallahassee lmao...
Member Since: October 28, 2006 Posts: 57 Comments: 29714
1973. sporteguy03
10:41 PM GMT on May 25, 2008
Good luck with that Michael.
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1972. Drakoen
10:42 PM GMT on May 25, 2008
I think i'm getting annoyed...
Member Since: October 28, 2006 Posts: 57 Comments: 29714
1970. Patrap
5:39 PM CDT on May 25, 2008


3:15 pm PDT NASA Blog Link
We've just completed the 90-minute (from EDL) poll, verifying that the Mars Odyssey orbiter, Mars Reconaissance Orbiter, and Mars Express are "go" for EDL communications support. While Mars Odyssey relays data back to Earth during EDL, Mars Reconaissance Orbiter will play back data later.

3:04 pm
For those of you who'd like to follow along on NASA TV, live shots are now being shown periodically from the MSA. There will be some interviews as well. We just completed voice checks as we make our way through the EDL procedure. If you notice folks referring to a thick book at their desks, this is the Approach and EDL procedure, several hundred pages long, that lists each step executed throughout our approach to and landing on Mars. This procedure, in fact, starts several weeks back. Also, the Project Manager just stopped by and wanted me to convey say hi to everyone reading on the web.
Member Since: July 3, 2005 Posts: 414 Comments: 125466
1967. Drakoen
10:37 PM GMT on May 25, 2008
1963. IKE 10:36 PM GMT on May 25, 2008
1960. Drakoen 5:35 PM CDT on May 25, 2008
1956. IKE 10:33 PM GMT on May 25, 2008
Actually it's slightly further north on this run...I stand corrected.

You're getting technical :)

Yeah...too technical..lol.


lol.
Member Since: October 28, 2006 Posts: 57 Comments: 29714
1966. moonlightcowboy
5:37 PM CDT on May 25, 2008
Very nice description of the EDL!
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1964. StormJunkie
10:35 PM GMT on May 25, 2008
Pat, Why didn't they use the rover landing technique? Seems a little safer then this jet engine stabilized landing.
Member Since: August 17, 2005 Posts: 26 Comments: 15472
1963. IKE
5:35 PM CDT on May 25, 2008
1960. Drakoen 5:35 PM CDT on May 25, 2008
1956. IKE 10:33 PM GMT on May 25, 2008
Actually it's slightly further north on this run...I stand corrected.

You're getting technical :)


Yeah...too technical..lol.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1961. Drakoen
10:35 PM GMT on May 25, 2008
1957. cchsweatherman 10:34 PM GMT on May 25, 2008
Don't be so quick Drak. At 168 hours, you can clearly see a trough sweeping across the Northern US creating a defined weakness in the ridge. It may push this east.


I know trust me. I was the first one to mention the shortwave over the U.S.
Member Since: October 28, 2006 Posts: 57 Comments: 29714
1960. Drakoen
10:34 PM GMT on May 25, 2008
1956. IKE 10:33 PM GMT on May 25, 2008
Actually it's slightly further north on this run...I stand corrected.


You're getting technical :)
Member Since: October 28, 2006 Posts: 57 Comments: 29714
1957. cchsweatherman
6:33 PM EDT on May 25, 2008
Don't be so quick Drak. At 168 hours, you can clearly see a trough sweeping across the Northern US creating a defined weakness in the ridge. It may push this east.
Member Since: April 14, 2007 Posts: 8 Comments: 5030

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About JeffMasters

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