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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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: 37860
406. surfmom
9:18 PM GMT on May 23, 2008
all4H - where are you??? you can bring those tadpoles in, change the water every couple of days and feed the fish food & algae flacks, Watch carefully (of put something on top of the bowl to keep them from jumping out) watch carefully --just before they get their legs their tail will start ti shrink and you will see little buds where the legs and arms are, Once they get their limbs and start to creep up the side of the bowl, let them go. My boys were forever saving them from drying up ponds and with the shortage of frogs we still grow and release as many as possible.
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405. seflagamma
5:21 PM EDT on May 23, 2008
Hi everyone, a quick scan back I saw a request for good radar on Florida. I have a really good one on my blog. here it is (I don't know how to link) hope it is not too big.

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404. Drakoen
9:20 PM GMT on May 23, 2008
No problem.
Member Since: October 28, 2006 Posts: 57 Comments: 30813
403. all4hurricanes
9:19 PM GMT on May 23, 2008
TADPOLES!!! We finally have tadpoles in Fairfax. I collected a few, and got on my boots to carry water to some tadpoles in a drying up pond. It looks like the large system east of the Philippians's is strengthening. I think it will take a similar course as Matmo (previous storm this year). Rain on Tuesday but we get a nice sunny break
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402. IKE
4:18 PM CDT on May 23, 2008
Yeah...thanks for posting that Drak.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
401. 0741
9:17 PM GMT on May 23, 2008
by when will we know if gfs is right i back for other hurr season
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400. surfmom
9:09 PM GMT on May 23, 2008
Thanks Drak - even though those pictures put a pit in my stomach, I understand the potential set-ups much better - a picture is worth 1000 words. A very good & easily understood explanation as well.

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399. all4hurricanes
9:12 PM GMT on May 23, 2008
TADPOLES!!! We finally have tadpoles in Fairfax. I collected a few, and got on my boots to carry water to some tadpoles in a drying up pond. It looks like the large system east of the Philippians's is strengthening. I think it will take a similar course as Matmo (previous storm this year). Rain on Tuesday but we get a nice sunny break
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398. IKE
4:07 PM CDT on May 23, 2008
What is causing the ghost storm to go north? A strong trough? That's what it looks like.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
397. KarenRei
9:07 PM GMT on May 23, 2008
I don't know if this has been covered yet, but I reported a swirl in the E. Pac. last night. Looks like there's another on the Caribbean side this morning:



Looks like the game is on.
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396. StormJunkie
9:04 PM GMT on May 23, 2008
379.

STL eluded to the the fact that the tornadoes this year rival the outbreak in 04 and it also seems that the steering patterns could be similar. Now, there is no official connection, but it will be interesting to see if his non-theory was correct.

346.

I'm confused?

Who's talking about who's mom ¿~)
Member Since: August 17, 2005 Posts: 26 Comments: 16874
395. IKE
4:02 PM CDT on May 23, 2008
Was this posted earlier on the 12Z ECMWF...from EAST Pac to the BOC?

Link
Member Since: June 9, 2005 Posts: 23 Comments: 37860
394. Drakoen
9:05 PM GMT on May 23, 2008
Mean SLP anomalies
Photobucket

This graphic is showing 1mb lower pressures in the climatological region where tropical cyclones take track in the Central Atlantic especially with a weak A/B high. The weaker pressures result in a weaker subtropical high, less subsidence, and less shearing from the tropical upper tropospheric trough.

Below are the Climatological tracks for storms in August and September with the Cape Verde season and peak season.




Mean Precip Anomalies are showing above-average precipitation again in the climatological tracks of Late July, August, September tropical waves and cyclones. Notice the extent from the Eastern African Highlands all the way through the Bahamas and Florida straits. The type of precipitation pattern could reflect where the majority of the systems go throughout J-A-S:
Photobucket

Last but not least the SST's which are still to remain in the .5-1C above average range:
Photobucket
Member Since: October 28, 2006 Posts: 57 Comments: 30813
393. atmoaggie
8:58 PM GMT on May 23, 2008
A better example of a storm intensifying over a shallow continental shelf would be Felix, which reintensified to a Cat 5 while over very shallow water, and extending over a long distance from land; the TCHP map shows almost no TCHP in that area (off Nicarauga). Also interesting is that SSTs fell by only a degree or so as Felix passed over; in fact, more cooling appears to have occurred over the deeper water further east (Aug 31, Sept 10).

Ah, yes. Very good example. And good points about the mapped THCP (depth included in the equation, the plotted values show the location of the shelf very well). The more extensive cooling in the deeper water makes perfect sense, too. Thanks.
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392. CaneAddict
8:57 PM GMT on May 23, 2008
Folks, The wave out in the Atlantic is very impressive as of now, However conditions will begin to become unfavorable so i don't expect much more development.....I am starting to believe that the GFS is positioning the low in the wrong area, I believe a system will develop in the East Pacific.....This is my opinion though, I am out, I'll be back tomorrow night!
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391. Weather456
4:55 PM AST on May 23, 2008
Interesting, the ECMWF further enforses the whole idea of an active cape verde season....

Central Tropical Atlantic - JAS

Lower Than Normal Pressure
Wetter Than Normal Conditions
Near Normal SSTs
Nuetral ENSO
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390. Midweststorm
8:53 PM GMT on May 23, 2008
Looks like wind sheer is forcast to drop a little bit ahead of the wave off africa.

I wonder if its going to be low enough to increase the waves strength?
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389. Weather456
4:53 PM AST on May 23, 2008
ECMWF Seasonal Forecasts
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387. cchsweatherman
4:51 PM EDT on May 23, 2008
Just to note, the 18UTC NAM develops a broad low in the Southwest Caribbean as well as an Eastern Pacific system. Thoughts? Maybe the NAM is now offering support to the GFS model? Below is the broad low and the Eastern Pacific system both developing in 84 hours.

Member Since: April 14, 2007 Posts: 8 Comments: 5169
385. cchsweatherman
4:50 PM EDT on May 23, 2008
382. HouseofGryffindor 4:49 PM EDT on May 23, 2008
Everyone have a great weekend. I'm out.


You too. See you here again on Monday (if not sooner).
Member Since: April 14, 2007 Posts: 8 Comments: 5169
384. Drakoen
8:49 PM GMT on May 23, 2008
Sure Jp. I'm still working on getting everything together.
Member Since: October 28, 2006 Posts: 57 Comments: 30813
381. cchsweatherman
4:39 PM EDT on May 23, 2008
Just based upon satellite presentation and QuikSCAT data, this tropical wave is quite impressive and appears to be moving towards the WNW towards 10N. Even though it looks deserving enough to become an invest, due to the worsening environmental conditions, I doubt it will get classified as an invest, but it would not surprise me to see it declared an invest. You may be absolutely correct 456; this may indeed be a classic Cape Verde season.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
380. TheCaneWhisperer
8:43 PM GMT on May 23, 2008
You have a problem WUmailing those thoughts to me drak? I have to leave and am interested in what you have to say.
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379. hurricanehanna
8:43 PM GMT on May 23, 2008
Hey Storm J! Pretty crazy weather we've been having nationwide. We even had a few tornadoes down here in Lafayette. Hope it's not an indication of what is to come!
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378. surfmom
8:43 PM GMT on May 23, 2008
IvanS, good to see you and most especially MO!
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377. surfmom
8:29 PM GMT on May 23, 2008
Finished work out east and raced to the beach to catch some waves in the gomexwater temp 81 degrees, wind @7knts from the East.waves were leftovers/ not really enough push, but three good rides & I'm happy --it'll be flatsville for a while again...no matter it was lovely to get wet, the water is warm, tourquise and it is a beautiful day out there --I call it "why I live here weather" bummer the rain more or less passed me by last night --just drizzle - not enough to make much of a difference. Pastures are still very thirsty - Hope my friends and favorite beach are OK in the Port St. Lucie/Fort Pierce area.
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376. atmoaggie
8:41 PM GMT on May 23, 2008
SJ, can probably add something to this...from before the schoolyard brawl over comments about someone's mother:

thanks atmo...here's my first question as an underground blogger...will the shelf provide a buffer to intensity if a storm was to make landfall mid-point of Louisiana..ie the Vermillion Basin??? There's different opinions on the so-called "shelf buffer"???

Got busy.
Don't count on a buffer, only a higher surge.

Seems that way sometimes...that a landfalling storm in the N Gulf will lose some power upon reaching the shelf, but it is really more a factor of other things: 1. Available dry air over land drawn into western side of approaching storms...dry air entrainment; 2. Increasing shear closer to 30 latitude (same sometimes applies to 30 lat over open Atlantic...but not always)

Humberto, last year, well avoided both of those and blew up over the shelf. Only into a cat 1, but if the conditions on the shelf were detrimental, I assure you that would not have happened.

The caveat: Usually by mid-summer, the full column of water over the shelf on the GoM will have warmed almost homogenously and there will be no shallow thermocline hiding cold water below. The TCHP (available heat content) on the shelf, in this case, is no less than that of the loop current. IF the full column of water has not warmed, upwelling, overturning, etc. can and does bring up cooler water under a storm. The effect depends on the forward speed and the difference in water temps.

As to storm surge, we N GoM folks have the shelf to blame for our records of surge height...far greater than surges in places without as much of a shelf, aka Miami. The shelf itself is responsible for some percentage of the surge height...knee-jerk response here is 30 to 40%.
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375. Drakoen
8:41 PM GMT on May 23, 2008
The ECMWF seasonal forecast was issued yesterday. Just got a look at the model today though. Showing some very interesting factors that I will post about shortly.
Member Since: October 28, 2006 Posts: 57 Comments: 30813
374. StormJunkie
8:35 PM GMT on May 23, 2008
Good to see ya again HH :~)

No need to lurk all season Mws, jump right on in.
Member Since: August 17, 2005 Posts: 26 Comments: 16874
373. KrazyKaneLove
8:34 PM GMT on May 23, 2008
finally getting rain here in Loxahatchee..nice soaking rain, nothing violent..hopefully this is all wpb will see..gotta go to work now..bbl
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372. hurricanehanna
8:30 PM GMT on May 23, 2008
Afternoon All. It's been a while, but as June 1 is looming and our local meteorologists are giving their Hurricane pep talks, figured its time to tune in and start paying attention to you guys. I learn more from ya'll than the national guys!
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371. Patrap
3:32 PM CDT on May 23, 2008
ATT text to voice version Link
Member Since: July 3, 2005 Posts: 428 Comments: 129780
370. HurricaneSammy
8:31 PM GMT on May 23, 2008
The National Weather Service in Melbourne has issued a

* Severe Thunderstorm Warning for...
southwestern Orange County in Florida.

* Until 500 PM EDT

* at 407 PM EDT... National Weather Service Doppler radar indicated a
severe thunderstorm capable of producing penny size hail... and
damaging winds in excess of 60 mph. This storm was located near
Walt Disney World and Lake Buena Vista... ... and moving east at 25 mph.

* Other locations in the warning include... but are not limited to...
mgm studios... epcot... Windermere... Bay Hill... Pleasure Island...
doctor Phillips... Universal studios... sea world... Oak
Ridge... Orlando... Pine Castle... Belle Isle... Buena Ventura
lakes... Conway... Orlando International Airport and Lake Mary Jane


Theme Parks and Highly Populations in the Area Afected

Not good ... Not good....

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369. Midweststorm
8:30 PM GMT on May 23, 2008
Afternoon all, came back just before the touch off of the season. Just gonna lurk again this year!
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367. HurricaneSammy
8:27 PM GMT on May 23, 2008
NWS: (Made By Them) NEW FLORIDA WARNINGS
Statement as of 4:22 PM EDT on May 23, 2008


... A Severe Thunderstorm Warning remains in effect until 445 PM EDT
for southeastern St. Lucie and northeastern Martin counties...

At 412 PM EDT... National Weather Service Doppler radar continued to
indicate a severe thunderstorm capable of producing nickel size
hail... and damaging winds in excess of 60 mph. This storm was
located near Port Salerno... or near Stuart... moving north at 9 mph.

Other locations in the warning include but are not limited to Port
Sewall... Snug Harbor... North River Shores... sewall's point... Rio...
Walton... Nettles Island... Waveland... Port Saint Lucie and Jensen
Beach

Lat... Lon 2700 8015 2706 8034 2732 8036 2733 8018
time... Mot... loc 2022z 199deg 8kt 2716 8019

Statement as of 4:09 PM EDT on May 23, 2008


The National Weather Service in Melbourne has issued a

* Severe Thunderstorm Warning for...
southwestern Orange County in Florida.

* Until 500 PM EDT

* at 407 PM EDT... National Weather Service Doppler radar indicated a
severe thunderstorm capable of producing penny size hail... and
damaging winds in excess of 60 mph. This storm was located near
Walt Disney World and Lake Buena Vista... ... and moving east at 25 mph.

* Other locations in the warning include... but are not limited to...
mgm studios... epcot... Windermere... Bay Hill... Pleasure Island...
doctor Phillips... Universal studios... sea world... Oak
Ridge... Orlando... Pine Castle... Belle Isle... Buena Ventura
lakes... Conway... Orlando International Airport and Lake Mary Jane

Severe thunderstorms produce damaging winds in excess of 58 miles an
hour and or large destructive hail. Frequent to excessive lightning
and very heavy rain will also be possible. If the storm approaches
you... seek shelter in an enclosed building on the lowest floor. Keep
away from windows.

Lat... Lon 2852 8112 2833 8113 2833 8149 2831 8153
2832 8161 2837 8165 2849 8165 2851 8163


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366. Patrap
3:29 PM CDT on May 23, 2008
Friday...Boingggggggggggggggggg!!!!!!

Member Since: July 3, 2005 Posts: 428 Comments: 129780
365. StormJunkie
8:28 PM GMT on May 23, 2008
Evening all :~)

See ya wmw, Have a good weekend
Member Since: August 17, 2005 Posts: 26 Comments: 16874
364. bystander
8:28 PM GMT on May 23, 2008
Good one JP!
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363. kmanislander
8:28 PM GMT on May 23, 2008
I'm out. BBL
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362. weathermanwannabe
4:27 PM EDT on May 23, 2008
I'm out (until Tuesday) but everyone have a safe and happy Long Weekend (for those of us who still have to work)..............WW
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360. HurricaneSammy
8:25 PM GMT on May 23, 2008
359. nash28 8:25 PM GMT on May 23, 2008
Once again, everyone S of I-4 and I-75 get screwed with the storms....



I Wouldn't Say The Admin Love you Either ...Lol
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359. nash28
8:23 PM GMT on May 23, 2008
Once again, everyone S of I-4 and I-75 get screwed with the storms....

Member Since: July 11, 2005 Posts: 190 Comments: 16972
357. IpswichWeatherCenter
8:23 PM GMT on May 23, 2008
343. IpswichWeatherCenter 8:20 PM GMT on May 23, 2008


We have spin!

IPWC Tornado warning for MIAMI!


There isn't even a severe t-storm warning much less a tornado warning. Posting false information is dangerous.


I did *insert beep here* that up...
I meant I think there should be...

Sorry
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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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