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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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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356. bystander
8:23 PM GMT on May 23, 2008
What's up with the blog? See alot of previous posts showing up again.
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353. NEwxguy
8:21 PM GMT on May 23, 2008
come on season!!!
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352. Drakoen
8:20 PM GMT on May 23, 2008
343. IpswichWeatherCenter 8:20 PM GMT on May 23, 2008

We have spin!

IPWC Tornado warning for MIAMI!


I don't see any spin. That looks like a radar effect.
Member Since: October 28, 2006 Posts: 57 Comments: 30490
351. HurricaneSammy
8:20 PM GMT on May 23, 2008
345. HouseofGryffindor 8:20 PM GMT on May 23, 2008
Drak - I'm hoping admin will step up to the plate and start banning people when the season starts.


Me?
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350. Patrap
3:19 PM CDT on May 23, 2008
FireFox2 is the recommended browser for all your Blogging and Tropical Posting Needs.

(Its reccomended by the wunderground developers)
Member Since: July 3, 2005 Posts: 424 Comments: 128275
348. kmanislander
8:19 PM GMT on May 23, 2008
Drak

When the season comes Admin will post a reminder about the rules of the road and 24 hr. bans will be handed out left, right and center
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347. atmoaggie
8:17 PM GMT on May 23, 2008
Wow, HOG. That could potentially turn ugly. I see some merging cells on the composite reflectivity.
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346. Drakoen
8:19 PM GMT on May 23, 2008
341. kmanislander 8:19 PM GMT on May 23, 2008
JP

I do not see a stretched image. I noticed that after the blog was redesigned lasr year every image seems the same size to me regardless of what size I select for posting.

Prior to that I used to see the blog stretched at times


I don't see a stretched image either.
Member Since: October 28, 2006 Posts: 57 Comments: 30490
344. hahaguy
4:19 PM EDT on May 23, 2008
oh god drak ten times worse
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343. IpswichWeatherCenter
8:18 PM GMT on May 23, 2008


We have spin!

IPWC thinks there should be a Tornado warning for MIAMI!

(bad wording)
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342. Drakoen
8:18 PM GMT on May 23, 2008
We can't even get through a few afternoon thunderstorms over Florida without an argument. Just makes me wonder what the season will be like...
Member Since: October 28, 2006 Posts: 57 Comments: 30490
341. kmanislander
8:16 PM GMT on May 23, 2008
JP

I do not see a stretched image. I noticed that after the blog was redesigned lasr year every image seems the same size to me regardless of what size I select for posting.

Prior to that I used to see the blog stretched at times
Member Since: Posts: Comments:
340. Patrap
3:17 PM CDT on May 23, 2008
GOM 120 Hour Water Surface Temperature Forecast Model Link

GOM 60 Hour WAVE Forecast Model Link

GOM 120 Hour Surface Current Forecast Model Link
Member Since: July 3, 2005 Posts: 424 Comments: 128275
339. NEwxguy
8:15 PM GMT on May 23, 2008
HOG
Good point
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338. HurricaneSammy
8:15 PM GMT on May 23, 2008
333.

True ...

But Population Growth Around The ThemeParks In Orlando has had a BOOM in the Last Decades
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337. kmanislander
8:13 PM GMT on May 23, 2008
IWC

The low is pulling up to the WNW and once it reaches about 10N shear will likely do a number on it. The Westerlies do not ease off for another 7 to 8 weeks
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336. IpswichWeatherCenter
8:13 PM GMT on May 23, 2008
"HurricaneSammy says to IpswichWeatherCenter (private):
Can u Post These 2 Images on the DR.M BLOG:"


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335. NEwxguy
8:14 PM GMT on May 23, 2008
(((sigh)))
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334. HurricaneSammy
8:14 PM GMT on May 23, 2008
.... Lets TALK ABOUT WEATHER ... I have been Posting About Weather intill that Issue Came up
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332. HurricaneSammy
8:12 PM GMT on May 23, 2008
---- ALERT ---

Warning Has Been Issued For Orlando Area

If you are in The Theme Parks Take SHELTER NOW
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331. atmoaggie
8:11 PM GMT on May 23, 2008
310. HurricaneSammy 8:07 PM GMT on May 23, 2008
307. CaneAddict 8:05 PM GMT on May 23, 2008
303. Patrap 8:04 PM GMT on May 23, 2008
I suggest you get a Blog and go crazy Post there.

He Was Trying to Insult Me Not u ....

HurricaneSammy, I was NOT trying to insult you, I stated that what you did is claim that the National Weather Services outlook was your own, Which is a form of plagiarism...

Cane , I was Talking to Pat ( Who Said i Should go Crazy Post somewhere)


O------------M------------G

My suggestion might be to stop posting about it at all. Talking to one poster (without any benefit to others)? Use the email. Don't like what was said? Use the ignore. You have tools at your disposal to minimize the effect on anyone else.
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330. Drakoen
8:13 PM GMT on May 23, 2008
329. jphurricane2006 8:13 PM GMT on May 23, 2008
it would look better if it didnt stretch the screen so much

Try Firefox.
Member Since: October 28, 2006 Posts: 57 Comments: 30490
328. IpswichWeatherCenter
8:11 PM GMT on May 23, 2008


looking better
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327. CaneAddict
8:11 PM GMT on May 23, 2008
Oh alright.
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326. Ivansrvivr
8:02 PM GMT on May 23, 2008
It is very rare for storm activity here to be anything like the destructive weather that happens over most of the US. We get tons of lightning and more tons of rain and small hail and that is about all usually. Our tornados are usually f-0 or 1 waterspouts that occur during the summer mornings. We don't get "dryline" thunderstorms with baseball sized hail and mile wide tornados every spring like the mid west. But we do get very heavy rains, more lightning than anywhere else on the country, and tropical systems as often as anywhere in the country and that is enough.
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325. Drakoen
8:11 PM GMT on May 23, 2008
Some of you seriously need to grow up...
Member Since: October 28, 2006 Posts: 57 Comments: 30490
324. IpswichWeatherCenter
8:10 PM GMT on May 23, 2008
321. HurricaneSammy 8:09 PM GMT on May 23, 2008
292. TerraNova 8:01 PM GMT on May 23, 2008
The southern Florida storms do not exceed severe criteria (dont think they do, none of them have split or merged by the looks of it).

Make That 8 + ... 2 New Warnings


*blabs*

I think the fact that around 90% of florida is affected by this gives it a severe warning need NOW
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323. HurricaneSammy
8:09 PM GMT on May 23, 2008
310. HurricaneSammy 8:07 PM GMT on May 23, 2008
307. CaneAddict 8:05 PM GMT on May 23, 2008
303. Patrap 8:04 PM GMT on May 23, 2008
I suggest you get a Blog and go crazy Post there.

He Was Trying to Insult Me Not u ....

HurricaneSammy, I was NOT trying to insult you, I stated that what you did is claim that the National Weather Services outlook was your own, Which is a form of plagiarism...


Cane , I was Talking to Pat ( Who Said i Should go Crazy Post somewhere)
Member Since: Posts: Comments:
322. Patrap
3:09 PM CDT on May 23, 2008
GOES-12 3 Channel Atlantic Ocean View (Updated ~3 hours)Link
Member Since: July 3, 2005 Posts: 424 Comments: 128275
321. HurricaneSammy
8:08 PM GMT on May 23, 2008
292. TerraNova 8:01 PM GMT on May 23, 2008
The southern Florida storms do not exceed severe criteria (dont think they do, none of them have split or merged by the looks of it).


Make That 8 + ... 2 New Warnings ...
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320. NEwxguy
8:06 PM GMT on May 23, 2008
Pat,
Thanks,thats a great link.

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319. CaneAddict
8:07 PM GMT on May 23, 2008
310. HurricaneSammy 8:07 PM GMT on May 23, 2008
307. CaneAddict 8:05 PM GMT on May 23, 2008
303. Patrap 8:04 PM GMT on May 23, 2008
I suggest you get a Blog and go crazy Post there.

He Was Trying to Insult Me Not u ....


HurricaneSammy, I was NOT trying to insult you, I stated that what you did is claim that the National Weather Services outlook was your own, Which is a form of plagiarism...
Member Since: Posts: Comments:
318. IpswichWeatherCenter
8:07 PM GMT on May 23, 2008
312. kmanislander 8:07 PM GMT on May 23, 2008
H23

I had not looked at the TWD but I am even more impressed now. 1010mb; a fighter already LOL


Very good potential for the ATL at this time of the year...

Will prob form around June near florida!
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317. Patrap
3:08 PM CDT on May 23, 2008
National Hurricane Preparedness Week Link


History teaches that a lack of hurricane awareness and preparation are common threads among all major hurricane disasters. By knowing your vulnerability and what actions you should take, you can reduce the effects of a hurricane disaster. Hurricane Preparedness Week during 2008 will be held May 25th through May 31st.

The goal of this Hurricane Preparedness Web site is to inform the public about the hurricane hazards and provide knowledge which can be used to take ACTION. This information can be used to save lives at work, home, while on the road, or on the water.
Member Since: July 3, 2005 Posts: 424 Comments: 128275
315. hahaguy
4:08 PM EDT on May 23, 2008
just got a severe warning for st lucie now
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314. KrazyKaneLove
7:59 PM GMT on May 23, 2008
hey sammy, all is good here, still no rain, but it looks like it's coming..soon. Wpbf25 was just showing local weather..they said in the next hour to hour and a half palm beach county will get a soaking.
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313. IpswichWeatherCenter
8:06 PM GMT on May 23, 2008
308. Patrap 8:05 PM GMT on May 23, 2008 Hide this comment.
At least I can find the Dupage Severe Page "Link" and not turn a PHD's Blog entry into a Italicized post freak fest.


problem THE LINK DON'T WORK!!!
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312. kmanislander
8:05 PM GMT on May 23, 2008
H23

I had not looked at the TWD but I am even more impressed now. 1010mb; a fighter already LOL
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311. Drakoen
8:06 PM GMT on May 23, 2008
Can you guys leave Cane Addict alone? Everyday its the same drama and i'm personally tired of it. If you have something to say to him do it in PM.
Member Since: October 28, 2006 Posts: 57 Comments: 30490
310. HurricaneSammy
8:06 PM GMT on May 23, 2008
307. CaneAddict 8:05 PM GMT on May 23, 2008
303. Patrap 8:04 PM GMT on May 23, 2008
I suggest you get a Blog and go crazy Post there.


He Was Trying to Insult Me Not u ....

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309. TerraNova
4:05 PM EDT on May 23, 2008
I dunno sometimes you can have 10 warnings and no watch...I need to look up watch criteria again.
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307. CaneAddict
8:04 PM GMT on May 23, 2008
303. Patrap 8:04 PM GMT on May 23, 2008
I suggest you get a Blog and go crazy Post there.


I am not going crazy, I just implied that HurricaneSammy copied the NWS outlook and claimed it as his own....
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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.

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