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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1907. Drakoen
9:29 PM GMT on May 25, 2008
1905. StormJunkie 9:26 PM GMT on May 25, 2008
1894.

There is only one that carves the tablets in stone, and that forecaster, or comedy show, is no longer among us here on the blogs :~)


lol I know who you are talking about!
Member Since: October 28, 2006 Posts: 57 Comments: 30563
1906. Bamatracker
9:27 PM GMT on May 25, 2008
should we take a moment of silence SJ?
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1905. StormJunkie
9:24 PM GMT on May 25, 2008
1894.

There is only one that carves the tablets in stone, and that forecaster, or comedy show, is no longer among us here on the blogs :~)
Member Since: August 17, 2005 Posts: 26 Comments: 16872
1904. presslord
5:18 PM EDT on May 25, 2008
aspectre....I think I see a pinhole eye....
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1903. aspectre
9:16 PM GMT on May 25, 2008
1717. scottsvb "...your getting mostly the wrong info...these are mostly...wishcasters..."
1754. CaneAddict "...a few that so called "wish cast"...only come around when a category 5 is heading to Europe but they want it to come to Atlanta Georgia..."

You must have missed NASA's photo of the Cat.8 approaching landfall in Miami...

...and Melbourne and Moscow and Mumbai and...
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1902. cdo
9:10 PM GMT on May 25, 2008
wow, it is set to average....

Why do sepeate people basically post the same thing like 10 billion times here?
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1901. Drakoen
9:08 PM GMT on May 25, 2008
1900. FLWeatherFreak91 9:07 PM GMT on May 25, 2008
The GFS should be finished before 6, am I correct?


Yes if you mean am and not pm. In the 18z run it reaches 144hr at 6:30pm.
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1900. FLWeatherFreak91
5:07 PM EDT on May 25, 2008
The GFS should be finished before 6, am I correct?
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1899. Patrap
4:04 PM CDT on May 25, 2008
check your filter settings to the right
Member Since: July 3, 2005 Posts: 426 Comments: 128667
1898. cdo
9:03 PM GMT on May 25, 2008
Why can't I see Michael's posts?
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1897. aspectre
8:56 PM GMT on May 25, 2008
Anything up with the far eastern end of the NorthAtlantic cyclone MainDevelopmentRegion being 1.5to2degrees warmer than average?
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1895. FLWeatherFreak91
4:56 PM EDT on May 25, 2008
1894. Michael 4:56 PM EDT on May 25, 2008 Hide this comment.
Here it is written in STONE...

GFS/UKMET/Canadian/NOGAPS still showing a
disturbed area around the Yucatan this coming weekend


LOL. Got that everbody? There's no need for any more posts. Michael has verified the tropical weather for the next week
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1893. Patrap
3:54 PM CDT on May 25, 2008
roger da cookies Houston.
Member Since: July 3, 2005 Posts: 426 Comments: 128667
1892. Patrap
3:53 PM CDT on May 25, 2008
12:00 pm PDT 2pm EDT
Welcome back to the Phoenix landing blog Link being written from JPL in Pasadena, CA, where today engineers are anxiously awaiting the arrival of the Phoenix spacecraft at Mars. Less than seven hours from now, Phoenix will enter the Martian atmosphere, heading towards its landing site in the northern arctic plains of Mars. It was decided yesterday afternoon that no trajectory correction maneuver (TCM) would be needed last night, but left open the option for another TCM eight hours before landing. Likewise, it was again decided this morning that the spacecraft trajectory is close enough that no correction is needed today either. Sleeping bags and cots scattered throughout offices and cubicles hint at the long night team members have had making final preparations for EDL this afternoon. The final EDL parameters were uploaded to the spacecraft this morning, drawing to a close the task of preparing the spacecraft for landing. Everything from this point out will happen autonomously.

In addition, the final EDL timeline was issued just this morning. The table below shows the time at which important events will be taking place in the course of EDL.

Event Time (UTC) Time (PST)
Cruise Stage Separation 23:39:17 16:39:17
Turn-to-Entry 23:39:47 16:39:47
Entry 23:46:17 16:46:17
Nominal Plasma Black out start 23:47:05 16:47:05
Nominal Plasma Black out end 23:49:05 16:49:05
Nominal Heatshield Deployment 23:50:12 16:50:12
Nominal Lander Leg Deployment 23:50:22 16:50:22
Nominal Lander Separation 23:52:50 16:52:50
Nominal Touch Down 23:53:33 16:53:33
Member Since: July 3, 2005 Posts: 426 Comments: 128667
1891. StormJunkie
8:45 PM GMT on May 25, 2008
Pat, I think that is the same link that is under More Useful Links. Way less cookies from this site :~) Chronicle site just hammers ya with them!
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1890. Drakoen
8:48 PM GMT on May 25, 2008
The NOGAPS has a chance to redeem itself lol...
Member Since: October 28, 2006 Posts: 57 Comments: 30563
1889. FLWeatherFreak91
4:46 PM EDT on May 25, 2008
Many NWS districts are now mentioning the ghost system in their discussions:

this is from gainesville:

.LONG TERM...MOSTLY DRY CONDITIONS EXPECTED THROUGH THE LONG
TERM...BUT WILL NEED TO MONITOR FOR ANY DEVELOPMENT IN THE GULF OF
MEXICO AS GFS HAS BEEN QUITE PERSISTENT THE PAST FEW RUNS.
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1888. Skyepony (Mod)
8:32 PM GMT on May 25, 2008
A list of all the models..

This goes into some heavy discussion about how the models did last year. It was released in Febuary. Forecasters were better than the models within 100hrs. Unusual year with GFS & BAM on top with GFDL & NOGAPS on the bottom. The BAM ensamble~ no suprise since it is GFS based. GFS got a big boost doing so well on DEAN's long, straight track. Of note was the late models had a really poor year. This is mostly in part to many short lived storms, some of which like HUmberto intesifed quick. By the time the model ran it was near over or things had changed significantly.
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1887. Patrap
3:45 PM CDT on May 25, 2008
Mars Pulls Phoenix In
05.25.08, 3:15 p.m. EDT -- NASA's Phoenix Mars Lander sped on Sunday morning toward its arrival at Mars, as the tug of the Red Planet's gravity accelerated the craft during the final day of its trip from Earth to Mars.
Read more
Landing coverage begins: 6:30 p.m. Eastern, NASA TV on the Web Link

Phoenix was on track for anticipated entry into the atmosphere at 4:30p.m. Pacific Time and reaching the surface at 4:38 p.m. PDT, although confirmation of those events comes no sooner than 15 minutes, 20 seconds later, due to the time needed for radio signals to travel from Mars to Earth
Member Since: July 3, 2005 Posts: 426 Comments: 128667
1886. TexasRiverRat
8:43 PM GMT on May 25, 2008
I thought it was going to land around 6 something this afternoon?
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1885. presslord
4:44 PM EDT on May 25, 2008
ooopppssss....my bad....Pacific time...pay attention dummy.....
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1884. Patrap
3:43 PM CDT on May 25, 2008
Click on this feed from the Houston Chronicle SJ.
The nasa tv Link.Link

The Broadcast begins at 5:30 CDT

Landing is at 6:53 CDT
Member Since: July 3, 2005 Posts: 426 Comments: 128667
1883. Bamatracker
8:41 PM GMT on May 25, 2008
339pm discussion out of NWS Mobile

LONG TERM (THURSDAY THROUGH SUNDAY)...THE 5-WAVE PROG SHOWS WEAK
RIDGING REMAINING OVER THE WESTERN AND ALONG THE GULF COASTAL STATES
WHICH WILL TEND TO LIMIT CONVECTIVE DEVELOPMENT THROUGH THE PERIOD.
THE REMNANTS OF THE FRONTAL BOUNDARY DISSIPATE ON THURSDAY...BUT
STILL SUPPORTS SMALL POPS...WITH A SURFACE HIGH OVER THE WESTERN
ATLANTIC PROMOTING A LIGHT ONSHORE FLOW THROUGH SATURDAY. THE GFS
AND ECMWF HAVE A SYSTEM DEVELOPING IN THE WESTERN CARIBBEAN WELL
TIMED FOR THE SEASON WHICH BEGINS JUNE 1ST. BOTH MODELS HAVE HAD
GOOD CONTINUITY OVER THE LAST FEW DAYS WITH THIS FEATURE AND BRING
THE SYSTEM JUST NORTH OF THE YUCATAN PENINSULA ON SUNDAY. THIS
SYSTEM WARRANTS CLOSE SCRUTINY PER HPC LONG RANGE DISCUSSION. /29


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1882. Patrap
3:41 PM CDT on May 25, 2008
I've got hair too.

Member Since: July 3, 2005 Posts: 426 Comments: 128667
1881. presslord
4:40 PM EDT on May 25, 2008
it should be landing about now...will take about 15 mins to hear from it....
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1880. cchsweatherman
4:38 PM EDT on May 25, 2008
At least Patrap isn't Jim Cantore. If he was Jim Cantore, I'd be worried for Jacksonville. LOL
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1879. Drakoen
8:37 PM GMT on May 25, 2008
Whats with the exclusion of the NOGAPS in all these NWS discussions. They can include the CMC but not the NOGAPS....
Member Since: October 28, 2006 Posts: 57 Comments: 30563
1878. stormlvr
8:31 PM GMT on May 25, 2008
1717. scottsvb 5:51 PM GMT on May 25, 2008
david your getting mostly the wrong info if you want to be educated here.. most professional Mets arent on these and these are mostly guesscasters or wishcasters. Its a fun place for speculation. Some are good non mets on here but alot spot out every model and believe "its the 1" cause that model eigther shows the storm getting stronger or heading their way.

Remember models change from run to run, soo many dynamics go into each run. A system that isnt developed yet gives us no idea on where it may go cause only 100 miles off can pick up a trough or weakness and take it off the long range run. Models are good forecasting where a area "might" develop within 3 days. After that the % rate of the models drops.

Any info you or anyone needs is best learned from the NHC or Mets.

I think Scott might be surprised who may visit and comment on this blog from time to time. I have seen forecasters who couldn't properly time the back edge of a precip shield and incorporate it into their forecast. There are good mets and bad mets just like anything else. Personally, I think that some of you have missed your calling or are on the right track depending on your age LOL
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1877. StormJunkie
8:38 PM GMT on May 25, 2008
Pat, Is the landing going to be covered live on Nasa TV?
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1876. Bamatracker
8:36 PM GMT on May 25, 2008
whats that patrap...your expecting a storm in jax between the 29th ot 2nd?!!!
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1875. TexasRiverRat
8:35 PM GMT on May 25, 2008
HOU/Galv says:

THE GFS AND ECMWF WERE DIFFERING IN THEIR HANDLING OF THE TROPICS
BY DAY SEVEN. THE GFS HAS A WEAKNESS IN THE UPPER RIDGE PRESENT
OVER THE ENTIRE GULF COAST STATES. THE ECMWF HAD A STRONGER RIDGE
IN PLACE FROM MEXICO ALL THE WAY EAST INTO FLORIDA. THE GFS AND
ECMWF DEVELOP A SURFACE LOW IN THE SOUTHERN CARIBBEAN BY THE
UPCOMING WEEKEND...WITH BOTH MODELS THEN GOING IN DIFFERENT
DIRECTIONS WITH THE SYSTEM. GIVEN THE TIME OF YEAR IT IS BEST TO
SAY THAT THE TROPICS BEAR WATCHING.
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1874. Patrap
3:34 PM CDT on May 25, 2008
Did I mention I'll be in Jax from the 29th-2nd ?

LOL
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1873. Bamatracker
8:34 PM GMT on May 25, 2008
crap....hope it doesn't shift to the west. I don't feel like boarding up yet!!!
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1872. CaneAddict
8:33 PM GMT on May 25, 2008
1868. Weather456 8:31 PM GMT on May 25, 2008
1866. CaneAddict 4:29 PM AST on May 25, 2008

LOL!!!


lol, anyway 456 and all others i am off for a bit, I'll be back when the 18Z model runs come out! BBL
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1871. StormJunkie
8:33 PM GMT on May 25, 2008
Holy Toledo Batman, a TS CAT 1 is about to hit Pensacola!!!

!~)
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1870. presslord
4:32 PM EDT on May 25, 2008
yup....Pensacola futures are way down today.....
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1869. Bamatracker
8:30 PM GMT on May 25, 2008
hey everyone....i think there is a very good chance we could be looking at a TS or cat 1 going into pensacola next week.

LOL!!!
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1868. Weather456
4:30 PM AST on May 25, 2008
1866. CaneAddict 4:29 PM AST on May 25, 2008

LOL!!!
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1867. Patrap
3:29 PM CDT on May 25, 2008

The spacecraft's speed relative to Mars increased from 6,300 miles per hour at 8:30 a.m. Pacific Time to 8,500 mph at 12:30 p.m., headed for a speed higher than 12,000 mph before reaching the top of the Martian atmosphere.
Link



Member Since: July 3, 2005 Posts: 426 Comments: 128667
1866. CaneAddict
8:24 PM GMT on May 25, 2008
1857. CaneAddict 4:17 PM AST on May 25, 2008
1830. Drakoen 8:03 PM GMT on May 25, 2008
Wonder what Arthur will be like...

LOL, the day Arthur forms you can bet this blog to go through 30 pages of comments like never before....The first storm tends to always be the most exciting...after a good 6-8 month spree of no tropical activity the first storm hypes everyone up..just to see a track drawn by the NHC for the system or the satellite presentation of a nice circulation....that's when the season really starts :-)!

And imagine, it cud potentially enter the GOM. The wishcasters will be out in their numbers.


LOL! The track is taking it straight into the Keys. Wishcaster says "IMO that area is going to do a 360 flip backwards and go in four circles over the loop eddy current and high TCHP and become a category five and come hit us here in Texas...Then it's gonna go back to the loop eddy current and sit there for 5 hours and rapidly intensify and come back again". HAHA
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1865. Patrap
3:21 PM CDT on May 25, 2008
Vary interesting Skyepony.
Member Since: July 3, 2005 Posts: 426 Comments: 128667
1864. Weather456
4:21 PM AST on May 25, 2008
1857. CaneAddict 4:17 PM AST on May 25, 2008
1830. Drakoen 8:03 PM GMT on May 25, 2008
Wonder what Arthur will be like...

LOL, the day Arthur forms you can bet this blog to go through 30 pages of comments like never before....The first storm tends to always be the most exciting...after a good 6-8 month spree of no tropical activity the first storm hypes everyone up..just to see a track drawn by the NHC for the system or the satellite presentation of a nice circulation....that's when the season really starts :-)!


And imagine, it cud potentially enter the GOM. The wishcasters will be out in their numbers.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1863. StormJunkie
8:21 PM GMT on May 25, 2008
That place gets crazy on the weekends now press. Hard to get on and off the island.

Did I miss anything with the 12z runs? Anyone want to fill me in before I look?

pat T - 3hrs 28min!!!
Member Since: August 17, 2005 Posts: 26 Comments: 16872
1862. CaneAddict
8:21 PM GMT on May 25, 2008
1860. presslord 8:20 PM GMT on May 25, 2008
I've got $100 bucks says someone will now quote Pat as predicting a storm will hit Pensacola next week....


LOL, Now that you said it, NO ONE will say anything lol.
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1861. Patrap
3:20 PM CDT on May 25, 2008
hey, I saw where someone is saying Pensacola is gonna get hit?,
Can I get that link?

LOL
Member Since: July 3, 2005 Posts: 426 Comments: 128667
1860. presslord
4:19 PM EDT on May 25, 2008
I've got $100 bucks says someone will now quote Pat as predicting a storm will hit Pensacola next week....
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1859. Skyepony (Mod)
7:56 PM GMT on May 25, 2008
I'm certainly suprised by the NOGAPS. Cat 5s didn't look that impressive on it last year. Should be interesting to see how each model handles things this year.
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1858. Patrap
3:17 PM CDT on May 25, 2008
UNYSIS GFSx 2JUNE 0Z surface Link
Member Since: July 3, 2005 Posts: 426 Comments: 128667
1857. CaneAddict
8:12 PM GMT on May 25, 2008
1830. Drakoen 8:03 PM GMT on May 25, 2008
Wonder what Arthur will be like...


LOL, the day Arthur forms you can bet this blog to go through 30 pages of comments like never before....The first storm tends to always be the most exciting...after a good 6-8 month spree of no tropical activity the first storm hypes everyone up..just to see a track drawn by the NHC for the system or the satellite presentation of a nice circulation....that's when the season really starts :-)!
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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.

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