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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2307. Chicklit
2:37 AM GMT on May 26, 2008
Low shear, low dust, warm water mean system development.
That's a fact. Where they'll go is something else entirely.
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2306. moonlightcowboy
9:37 PM CDT on May 25, 2008
2296. No, it's not. My comment was actually negative, as in "ugh" for storms passing through! The longer that area is bombarded by those hot rays, etc, TCHP is just going to expand and get deeper.
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2305. Bamatracker
2:37 AM GMT on May 26, 2008
the point of a range in the forecast is a testimate to lack of forecasting skill we have for the number of storms and that all regardless of the final number should be prepared for the one that actally finds them.
Member Since: May 17, 2006 Posts: 6 Comments: 1367
2304. pearlandaggie
2:38 AM GMT on May 26, 2008
Epsi-what? LOL...I'll have to go look that one up!
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2303. Stormchaser2007
10:37 PM EDT on May 25, 2008
Dot even get me started about EPSILON....lol.

"There are no clear reasons and I am not going to make one up to explain the recent strengthening of Epsilon"
Avila-2005.
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2302. Stormchaser2007
10:36 PM EDT on May 25, 2008
Night Baha....
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2301. StormJunkie
2:35 AM GMT on May 26, 2008
kman, that is not exactly fair. The NHC forecast is for 12-16 storms.
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2300. pearlandaggie
2:35 AM GMT on May 26, 2008
kman...there is NO WAY NOAA could be wrong! you need an attitude adjustment, sir! LOL

the forecast for Rita involved THE ENTIRE Texas coastline, only to have landfall in Louisiana! :)
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2299. Chicklit
2:33 AM GMT on May 26, 2008
Remember Felix last year, how quickly it formed into the 'perfect storm' under perfect conditions? And then all of those systems that died under shear in the Antilles.
People here are all over the Caribbean, Fla. Peninsula and Gulf. And the expertise, interest levels all different...So we'll see, won't we? Certainly, will be interesting.
We're getting a nice wide berm of sand on our beaches right now. Give credit to Ponce Inlet Authority using Intracoastal dredge material to shore up the critically eroded beaches. Way to go, guys! I love it when people do what they say they're going to do.
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2298. moonlightcowboy
9:36 PM CDT on May 25, 2008
Have a good sleep, Baha, and thanks.
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2297. Stormchaser2007
10:35 PM EDT on May 25, 2008
Oh my bad Noaa is forecasting 12-16 storms....well with a forecast that vague whats the point of even giving one....
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2296. Weather456
10:29 PM AST on May 25, 2008
Also, dry air over the Caribbean isnt necessarily a good thing...today on visible imagery I saw the full extent of the Earth's albedo (the sun's reflection) gleaming over the cloud-free skies of the Caribbean basin, an indicator the sea surface was receiving max insolation. Currently the sun's overhead angle is 15 degrees north.....at 23.5N on June 21.
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2295. BahaHurican
10:30 PM EDT on May 25, 2008
Good night everybody.
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2294. kmanislander
2:33 AM GMT on May 26, 2008
Why is NOAA only forecasting 12 storms then.


Maybe they are wrong
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2293. Stormchaser2007
10:33 PM EDT on May 25, 2008
2281

Puters started eating their data at 8:00 est (00z) but won't start regurgitating it until midnightish. All models should be out by around 2am.

Puters take a lot of time to digest all that info :~)


Dang SJ you make the puters sound like me after my Christmas dinner.
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2292. StormJunkie
2:32 AM GMT on May 26, 2008
2284 Sorry, that should have said 2273 on that post.
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2291. pearlandaggie
2:32 AM GMT on May 26, 2008
nevermind...i am in error...weird how the other one wouldn't post!
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2290. Stormchaser2007
10:32 PM EDT on May 25, 2008
Why is NOAA only forecasting 12 storms then.
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2289. StormJunkie
2:30 AM GMT on May 26, 2008
2281

Puters started eating their data at 8:00 est (00z) but won't start regurgitating it until midnightish. All models should be out by around 2am.

Puters take a lot of time to digest all that info :~)
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2288. pearlandaggie
2:31 AM GMT on May 26, 2008
trying a different one...

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2287. kmanislander
2:28 AM GMT on May 26, 2008
Chicklit

Neutral conditions with ENSO and low dust are two of the factors favouring active conditions.



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2286. Stormchaser2007
10:29 PM EDT on May 25, 2008
Michfan 10:28 PM EDT on May 25, 2008 Hide this comment.
When do the 00z runs of the models start?


I think they start at 11:30....dunno though.
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2285. cchsweatherman
10:27 PM EDT on May 25, 2008
Now, I realize the NAM sucks forecasting tropical systems, but it does develop a tropical low just north of Panama in 60 hours.
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2284. Stormchaser2007
10:28 PM EDT on May 25, 2008
aw dang..
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2283. pearlandaggie
2:28 AM GMT on May 26, 2008
well, apparently i can't post pics...

so here's the Link
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2282. kmanislander
2:26 AM GMT on May 26, 2008
SSTs and TCHP should begin to sizzle then, soon, I'd think.


MLC, the moored buoys are showing SST of 82 and 83 in the central and NW Caribbean already.

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2281. Michfan
9:28 PM CDT on May 25, 2008
When do the 00z runs of the models start?
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2280. moonlightcowboy
9:27 PM CDT on May 25, 2008
Pearland, lol, some folks are just fashionably late! ; P
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2279. Stormchaser2007
10:25 PM EDT on May 25, 2008
2270. Yeah I know just saying when your a kid unfortunately you wish everything was coming your way.(If hes not a kid then man will I fell like a jerk).
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2278. StormJunkie
2:26 AM GMT on May 26, 2008
2273, Thank you kind sir :~)

Love the zoom feature!
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2277. Chicklit
2:25 AM GMT on May 26, 2008
Yes, for sure Kman. What's with El Nino? With low shear and low dust we'd be in for some system formation.
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2276. pearlandaggie
2:23 AM GMT on May 26, 2008
Solar Cycle 24....where are you?



it will be interesting to see if the late-to-the-party solar cycle 24 and subsequent increased cloud cover will affect the '08 hurricane season...
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2275. JLPR
10:26 PM AST on Mayo 25, 2008
2270.
I'm not LOL, I just can bet he lives in South Florida....figures.


If I remember correctly he lived in North or South Carolina
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2274. hahaguy
10:26 PM EDT on May 25, 2008
i hear ya kman
Member Since: August 12, 2007 Posts: 2 Comments: 2838
2273. aspectre
2:13 AM GMT on May 26, 2008
2233. StormJunkie "...where you scooping those pics from?

http://phoenix.lpl.arizona.edu/ or more specificly for images
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2272. kmanislander
2:23 AM GMT on May 26, 2008
Chicklit

Lets hope that is the only similarity to 2004 !!

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2271. StormJunkie
2:23 AM GMT on May 26, 2008
Yes it is JF, can't wait to see the color pics over the next few days.

lol kman, to think we went all that way, would have been a lot cheaper to go to your back yard I bet....
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2270. CaneAddict
2:21 AM GMT on May 26, 2008
100, 200 Comments Sort: Newest First - Order Posted Filter: Show All Show Bad Show Below Average Show Average Show Good Show Best

2262. Stormchaser2007 2:21 AM GMT on May 26, 2008
Well you cant blame him for overestimating the intensity his name is junior meteorologist, cane.


I'm not LOL, I just can bet he lives in South Florida....figures.
Member Since: October 5, 2007 Posts: 3 Comments: 2151
2269. moonlightcowboy
9:21 PM CDT on May 25, 2008
2260. kmanislander 9:20 PM CDT on May 25, 2008
...Unbelievably dry year in the Caymans.


SSTs and TCHP should begin to sizzle then, soon, I'd think.
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2268. kmanislander
2:22 AM GMT on May 26, 2008
SJ

Did you snap a pic of my backyard ? LOL
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2267. Chicklit
2:20 AM GMT on May 26, 2008
Hi Kman...Yes, it's been very dry in Central Florida as well. Reminds me of '04 when my gardenias turned brown before blooming.
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2265. BahaHurican
10:14 PM EDT on May 25, 2008
2228. moonlightcowboy 10:00 PM EDT on May 25, 2008
Baha, thanks for clearing that up for us! I know nothing about them! But, I knew you would - and pretty sure I remember you talking about them last season.


Yeah, somebody started talking about them and I got curious. I did a fair amount of reading, though I didn't keep any links.
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2264. Stormchaser2007
10:21 PM EDT on May 25, 2008
SJ I thought that might be from last year....
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2263. CaneAddict
2:19 AM GMT on May 26, 2008
2236. juniormeteorologist 2:07 AM GMT on May 26, 2008
hey guys..I just made a prediction on the disturbance..JUST A PREDICTION!!


A disturbance that's not there as of yet. Also none of the models develop this area 250 miles south-west of Cuba like you are predicting...and a category 2 hurricane this time of year is like 1 and 100. Anyways nice prediction.
Member Since: October 5, 2007 Posts: 3 Comments: 2151
2262. Stormchaser2007
10:19 PM EDT on May 25, 2008
Well you cant blame him for overestimating the intensity his name is junior meteorologist, cane.
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2261. Chicklit
2:15 AM GMT on May 26, 2008
It will be interesting certainly to see what happens this year. And I am delighted to be in such good company!
What is the status of the El Nino--Neutral conditions? Has shear lessened?
By the way, now might be a good time to refill the 5 gallon gas containers and check to see if the generator's working.
I've got panels for my house. It's probably too late to order them for this year, but they're the cheapest and still very good protection. Also, wouldn't be a bad idea to check for hurricane clips on your rafters. Those are where the trusses meet the walls. There should be clips with at least six nails in them. If you don't have them, then you can put them in now, but in early morning before it gets too hot!
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2260. kmanislander
2:16 AM GMT on May 26, 2008
Hi Bama

All is well in the NW Caribbean except for the drought. Unbelievably dry year in the Caymans. First we had early rain in March then nothing for about 10 weeks. Makes me worry about the season when you get significant variations from the norm like this
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2259. StormJunkie
2:18 AM GMT on May 26, 2008
Yep sc07, we had nothing there to take that picture 4 hours ago :~)
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2258. CaneAddict
2:14 AM GMT on May 26, 2008
juniormeteorologist - You live in South Florida correct?
Member Since: October 5, 2007 Posts: 3 Comments: 2151
2257. Stormchaser2007
10:17 PM EDT on May 25, 2008
LOL kman, Sj is that recent footage?
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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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