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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2257. Stormchaser2007
10:17 PM EDT on May 25, 2008
LOL kman, Sj is that recent footage?
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2256. JRRP
2:12 AM GMT on Mayo 26, 2008
ok
but has a nice convection
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2255. StormJunkie
2:15 AM GMT on May 26, 2008
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2254. kmanislander
2:15 AM GMT on May 26, 2008
What dust ??

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2253. Stormchaser2007
10:13 PM EDT on May 25, 2008
Yeah I forgot to take that into consideration Baha.
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2252. Bamatracker
2:13 AM GMT on May 26, 2008
hey kman hows it going?
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2251. moonlightcowboy
9:13 PM CDT on May 25, 2008
2246. Little to no dust, right now.
Member Since: July 9, 2006 Posts: 184 Comments: 29594
2250. Weather456
10:12 PM AST on May 25, 2008
SC2007


A possible tropical wave across West Africa...still need some more evidence.



This is no doubt an african easterly wave across Central Africa



Member Since: July 24, 2005 Posts: 407 Comments: 19076
2249. StormJunkie
2:12 AM GMT on May 26, 2008
2236...

Serenity now!

Thanks wsp, did not know if you were just using a print screen, or if they had the actual images on the web yet.
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2248. kmanislander
2:12 AM GMT on May 26, 2008
CCHS

That Met hit the nail on the head; look at the Caribsat now !. Bone dry.
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2247. BahaHurican
10:11 PM EDT on May 25, 2008
2215.

That PDO signature is still mighty strong, though.
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2246. Chicklit
2:10 AM GMT on May 26, 2008
What does the African dust look like?
June 1st is right around the corner...
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2245. moonlightcowboy
9:11 PM CDT on May 25, 2008
2239. Nice!
Member Since: July 9, 2006 Posts: 184 Comments: 29594
2244. BahaHurican
9:59 PM EDT on May 25, 2008
On the Hebert boxes, this reaction to them is just what I'm talking about. I got the impression Hebert was making an OBSERVATION, not postulating a theory. And I don't think he ever implied that every storm that passes through the box will hit FL. It's the OTHER way around (i. e. the converse is not true).

If the storm hit Florida, it likely passed through one of those boxes first. That's all.

I think a more logical implication of the boxes is that storms won't likely come from other directions and then hit Florida. Basically all the HBs are is a cruder version of the current storm formation / track probabilities type chart we use all the time, linked to a specific state (actually to a particular portion of that state).

I believe in the boxes because they are simply an interpretation of climatology.
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2243. Stormchaser2007
10:08 PM EDT on May 25, 2008
Personally I like this view better.

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2242. tillou
2:09 AM GMT on May 26, 2008
All right now, let me put my two cents in as to what's going to happen here.

I think it is propable that something will develope in the WCAR in a couple of weeks just like the models are predicting.

The trough that is over Cuba will die out and stall. This will moisten up the CAR. After lingering in the WCAR for a while, some storms will start firing and I think we all know what till happen next.

Of course time will only tell, but its way too early to state were it will end up.
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2241. Weather456
10:07 PM AST on May 25, 2008
2235. JRRP 10:06 PM AST on May 25, 2008

the one further east is an AEW but the one along the coast still to be seen.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2240. weathersp
10:03 PM EDT on May 25, 2008
NASA TV SJ.
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2239. cchsweatherman
10:08 PM EDT on May 25, 2008
Just got a response back from NBC6 Meteorologist John Gerard and here is what he had to say.

We've been watching it but not mentioning it on the air. If we mentioned everything the 10-day GFS predicted we'd be wrong 75% of the time. I am already noticing a westward shift in the model track with high pressure building south across the central U.S. next week. Here we are talking about something that hasn't even formed yet, isn't this crazy? Look at the CaribSat and it's virtualy clear right now. Hmmmm. But yes, it is worth watching if anything out of respect for the day to day consistency the models have been showing the past week or so.
Member Since: April 14, 2007 Posts: 8 Comments: 5157
2238. kmanislander
2:07 AM GMT on May 26, 2008
Looks like the TPC are buying into the eastward propagating system from the EPAC

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2237. Stormchaser2007
10:06 PM EDT on May 25, 2008
Wow JRRP thats one nice looking area over Africa.456 what do you make of it, do you think its a wave.
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2236. juniormeteorologist
2:04 AM GMT on May 26, 2008
hey guys..I just made a prediction on the disturbance..JUST A PREDICTION!!



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2235. JRRP
1:58 AM GMT on Mayo 26, 2008

could be the next wave!!!
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2234. Bamatracker
2:04 AM GMT on May 26, 2008
just watched the first pics from mars....pretty awesome!!!!
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2233. StormJunkie
2:02 AM GMT on May 26, 2008
wsp, where you scooping those pics from?
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2232. pearlandaggie
2:01 AM GMT on May 26, 2008
you guys had better watch that "off-topic" stuff before you earn yourself a ban! LOL
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2231. Stormchaser2007
10:00 PM EDT on May 25, 2008
So theres different likelihoods of landfall with each box. Never knew that, thanks Baha!!
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2230. weathersp
10:00 PM EDT on May 25, 2008
First Pictures of Mars Polar region...

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2229. pottery
9:59 PM AST on May 25, 2008
456, yes, I see that. I'll still be surprised.
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2228. moonlightcowboy
8:58 PM CDT 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.
Member Since: July 9, 2006 Posts: 184 Comments: 29594
2227. pottery
9:56 PM AST on May 25, 2008
2224. Its a pig farm. With lots of dead pigs..........
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2225. BahaHurican
9:32 PM EDT on May 25, 2008
2137. moonlightcowboy 9:01 PM EDT on May 25, 2008
- haha, I've heard several talk about the HBox before, but I've not gotten a great deal out of it's theory. Baha could probably give some good info on that!


Hey, how'd u know I was in here reading w/out posting?????

LOL

Hmmm . .. I think the Hebert boxes work fine as long as you don't take them out of context. If I remember correctly Hebert's theory was that 90% of hurricanes that hit Florida travel through one of two "boxes", one east of PR, one east of the Yucatan. I've seen this misinterpreted to say if a storm passes through one of the boxes it has a 90% chance of hitting Florida. THESE ARE NOT THE SAME THING!!!

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2224. Skyepony (Mod)
1:53 AM GMT on May 26, 2008
Official: Storm kills 1 in Minnesota; 20 missing
Published: 5/25/08, 9:45 PM EDT
By JOSHUA FREED
HUGO, Minn. (AP) - Severe thunderstorms packing large hail and possible tornadoes rumbled across the nation's midsection on Sunday, killing at least one person, injuring nine others and damaging dozens of homes.

At least 20 people were unaccounted for after a swift storm blew through the St. Paul suburb of Hugo, damaging about four dozen homes, City Administrator Mike Ericson said. Many of them could be out of town for the holiday weekend, he said


I can't figure out what that was in the damage photo.
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2223. Weather456
9:50 PM AST on May 25, 2008
2214. pottery 9:48 PM AST on May 25, 2008

That is true but for the Carib basin. Remember most models show the intial disturbance will oringinate in the EPAC not in the Caribbean sea.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2222. Stormchaser2007
9:51 PM EDT on May 25, 2008
LOL MLC! Yeah K-man just had my shutters installed last week around Tuesday. Man those things cost me an arm and a leg!
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2221. Stormchaser2007
9:49 PM EDT on May 25, 2008
Hmm things will have to moisten up rather fast for anything to develop in the coming days.
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2220. kmanislander
1:48 AM GMT on May 26, 2008
Hi Stormchaser

I am doing well thanks. Got half my PGT hurricane impact windows installed with the rest to go in this week so i will be ready if anything comes along.

Right now, nothing on the horizon.
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2219. moonlightcowboy
8:45 PM CDT on May 25, 2008
- Chaser, no worries, glad you did! Post away! LOL

- K'man, see, you know the conditions, have the "hands-on" feel there and experience, too. I'll take that over models any day! I'm not saying they're not helpful, they're just tools in the arsenal. But, not a "be-all, end-all" to cyclogenesis and to track either.
Member Since: July 9, 2006 Posts: 184 Comments: 29594
2217. StormJunkie
1:48 AM GMT on May 26, 2008
Evening LC, good to see ya out and about :~)

And thanks for your awesome blog! Fine job!
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2216. nash28
1:48 AM GMT on May 26, 2008
As I said earlier, any FL storm, and the crew and I are headed out with video, still shots and help for cleanup.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
2215. Stormchaser2007
9:47 PM EDT on May 25, 2008
We are about neutral now...
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2214. pottery
9:39 PM AST on May 25, 2008
Looking at the loops and images, and the models.
Right now, the only moisture in the Tropics of any note, is on the coast of west Africa, northern South America, and Central America. All of it is over land at the moment.
There is plenty of dry air over the trop. Atl, the Carib. sea, and the GoM.
I am with Kman. I would be very suprised to see any development this week.
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2213. LowerCal
6:47 PM PDT on May 25, 2008
First images from Mars Phoenix Lander any minute on NASA TV Public Channel.
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2212. Stormchaser2007
9:45 PM EDT on May 25, 2008
Hello kman how are you?
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2211. nash28
1:45 AM GMT on May 26, 2008
Michael- We heard you. We get it dude. And I lived through the 2004 and 2005 seasons thank you. FL has had enough for many years to come.

Thanks for the brilliant insight though.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
2210. Michfan
8:44 PM CDT on May 25, 2008
If the NOGAPS hadn't hoped on board as strong as it did i think we would be looking at it somewhat more skeptically. Its very unusual for it to churn up a storm as strong as this.
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2209. Stormchaser2007
9:44 PM EDT on May 25, 2008
The odds of TX getting a major hurricane this year is just as great as FL getting a major hurricane. In other words, shut up and watch the show

Wow a bit edgy are we now...
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2207. nash28
1:43 AM GMT on May 26, 2008
What has my eye is the NOGAPS for now. Usually fairly conservative. Two straight runs spinning up a system in the CB, not the EPAC. For now anyways, the EPAC solution is fading.
Member Since: July 11, 2005 Posts: 190 Comments: 16972

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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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