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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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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306. hurricane23
4:04 PM EDT on May 23, 2008
280. kmanislander 3:56 PM EDT on May 23, 2008
Hi Adrian,

Great loop. It looks like that low is on a WNW heading

Hey Kman!

Yea pretty impressive wave structure wise for late may.I noted earlier that the NHC added it to the 12z surface map with a 1010mb low.

Here is what TPC had to say about 2hrs ago.

A WELL DEFINED TROPICAL WAVE IS ALONG 27W/28W S OF 13N MOVING W
10-15 KT. A 1010 MB LOW WAS ADDED ALONG THE WAVE AXIS NEAR 6N...
BASED ON PRONOUNCED LOW-LEVEL TURNING APPARENT ON VISIBLE IMAGES
AND A FAIR AMOUNT OF CURVATURE IN AN EARLIER QSCAT PASS...
DESPITE MUCH RAIN FLAGGING. CONVECTION IS CONFINED TO AN AREA N
OF THE LOW CENTER FROM 7N-9N BETWEEN 26W-29W
.

Environment ahead of the wave is not the greatest but its may so its expected.
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305. HurricaneSammy
8:02 PM GMT on May 23, 2008
BBL Just going outside to .... Watch the Thunderstorm Approach ...and then See the Downpoor
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304. CaneAddict
8:03 PM GMT on May 23, 2008
Haha, Patrap!
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303. Patrap
3:03 PM CDT on May 23, 2008
I suggest you get a Blog and go crazy Post there.
Member Since: July 3, 2005 Posts: 421 Comments: 127592
302. hurricane23
4:02 PM EDT on May 23, 2008
.
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301. IpswichWeatherCenter
8:00 PM GMT on May 23, 2008
289. HurricaneSammy 8:00 PM GMT on May 23, 2008 Hide this comment.
278. IpswichWeatherCenter 7:56 PM GMT on May 23, 2008

The Nws Still Has Not Issued a Severe Watch ....

We Have Had 6 + Warnings they Should Make one


good point

I had always thought that 6 to 10 warnings = a serve to ZOMG WE WILL DIE warning
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300. CaneAddict
8:02 PM GMT on May 23, 2008
286. Patrap 7:59 PM GMT on May 23, 2008
er..its Plagiarism

Plagiarism is the practice of claiming or implying original authorship of (or incorporating material from) someone else's written or creative work,

Same Thing they Tought Us In School ...


Did you not see my comment, That's exactly what you did! You copied the NWS warnings and posted it as " By" Hurricanesammy.
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299. Patrap
3:02 PM CDT on May 23, 2008
Clarification,education,.LOL

Every post dont come with a Point.
I aint a Pencil,..
Member Since: July 3, 2005 Posts: 421 Comments: 127592
298. HurricaneSammy
8:01 PM GMT on May 23, 2008
Post this Image Please

http://flame.fl-dof.com/fire_weather/KBDI/index.html

Then Post this one


http://flame.fl-dof.com/fire_weather/KBDI/rainfall_map.html

" For Some Reason I can't Post Images "
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296. atmoaggie
7:59 PM GMT on May 23, 2008
" If you Live in S.Florida Press 111"

And then "2" for English (used to be press 1 for English...changed based on demand)
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295. CaneAddict
8:01 PM GMT on May 23, 2008
286. Patrap 7:59 PM GMT on May 23, 2008
er..its Plagiarism

Plagiarism is the practice of claiming or implying original authorship of (or incorporating material from) someone else's written or creative work, ...


Whats your point Pat? He did exactly that. lol
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294. Drakoen
7:57 PM GMT on May 23, 2008
That tropical wave with a low along the wave axis is interesting. An upper level trough is just to the west is creating strong southerly wind shear which is why most of the convection is on the northern end of the low which is the main inhibitor of the systems development. Water vapor imagery of the mid to upper levels of the atmosphere suggest moist conditions.
Member Since: October 28, 2006 Posts: 57 Comments: 29904
293. kmanislander
7:58 PM GMT on May 23, 2008
While climatology says it should not develop the shear tendency just ahead of it has been falling.

Hard to believe there is something that far out to be talking about before July.
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292. TerraNova
4:00 PM EDT 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).
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291. HurricaneSammy
8:00 PM GMT on May 23, 2008
286. Patrap 7:59 PM GMT on May 23, 2008
er..its Plagiarism

Plagiarism is the practice of claiming or implying original authorship of (or incorporating material from) someone else's written or creative work,


Same Thing they Tought Us In School ...

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289. HurricaneSammy
7:58 PM GMT on May 23, 2008
278. IpswichWeatherCenter 7:56 PM GMT on May 23, 2008

The Nws Still Has Not Issued a Severe Watch ....

We Have Had 6 + Warnings they Should Make one
Member Since: Posts: Comments:
288. atmoaggie
7:57 PM GMT on May 23, 2008
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%.

Found this somewhat interesting article discussing the feasibility of pumping cold deep water onto the shelf to weaken hurricanes. Weird, but maybe ... ?
Link
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287. smmcdavid
2:57 PM CDT on May 23, 2008
Well, I hope you FL guys get soaked! I can honestly wait for any excitement in the atlantic.
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286. Patrap
2:58 PM CDT on May 23, 2008
er..its Plagiarism

Plagiarism is the practice of claiming or implying original authorship of (or incorporating material from) someone else's written or creative work, ...
Member Since: July 3, 2005 Posts: 421 Comments: 127592
285. CaneAddict
7:55 PM GMT on May 23, 2008
276. HurricaneSammy 7:55 PM GMT on May 23, 2008
FLORIDA CURRENT WARNINGS
By: HurricaneSammy


That is plagiarism ......You didn't type all of that. Don't EVER post the NWS work as if it's yours.
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284. HurricaneSammy
7:56 PM GMT on May 23, 2008
221. KrazyKaneLove 7:19 PM GMT on May 23, 2008
I'm actually west of wpb so I'll let you know what this storm is doing...The mets never say anything local til west palm is already getting whacked I noticed..lol

U Ok?
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283. hahaguy
3:57 PM EDT on May 23, 2008
been good jp
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282. Ivansrvivr
7:54 PM GMT on May 23, 2008
273. Just some active afternoon thunderstorms over S.Florida mostly. It a tad too early for anything major to be happening in the tropics for us is the Atlantic Basin.
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281. KrazyKaneLove
7:54 PM GMT on May 23, 2008
just a bunch of thirsty, drought stricken floridians eager for rain...me included
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280. kmanislander
7:53 PM GMT on May 23, 2008
Hi Adrian,

Great loop. It looks like that low is on a WNW heading
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278. IpswichWeatherCenter
7:55 PM GMT on May 23, 2008


New warnings!

Statement as of 3:42 PM EDT on May 23, 2008

... The Severe Thunderstorm Warning for west central Miami-Dade County
is cancelled...

The thunderstorm that prompted the warning over urban west central
Miami-Dade County has weakened. Therefore... the Severe Thunderstorm
Warning has been cancelled for west central Miami-Dade County.

Thunderstorms remain in the urban west central Miami-Dade County
which will drift to the east... and affect Tamiami Trail and krome
Avenue. Frequent lightning... gusty winds to 40 mph... very heavy
rainfall... and small hail are still possible. Stay tuned to NOAA
Weather Radio or local media for the latest updates.

Lat... Lon 2586 8063 2559 8068 2573 8087 2585 8088
time... Mot... loc 1942z 270deg 6kt 2580 8063

tatement as of 3:30 PM EDT on May 23, 2008

The National Weather Service in Jacksonville has issued a

* Severe Thunderstorm Warning for...
northeastern Marion County in northern Florida
southeastern Putnam County in northeast Florida
western Flagler County in northeast Florida

* until 415 PM EDT

* at 330 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
Salt Springs... and moving northeast at 30 mph.

* The severe thunderstorm will be near...
Pomona Park by 345 PM EDT...
Satsuma... Pomona Park and Crescent City by 350 PM EDT...
Andalusia by 355 PM EDT...
San Mateo... Palatka and Andalusia by 400 PM EDT...

This is a dangerous storm. If you are in its path... prepare
immediately for damaging winds... destructive hail... and deadly cloud
to ground lightning. People outside should move to a shelter...
preferably inside a strong building but away from windows.

Report severe weather or damage to the nearest law enforcement agency
or your County emergency management.

Lat... Lon 2935 8146 2936 8150 2933 8161 2931 8165
2929 8165 2923 8182 2938 8193 2969 8165
2940 8133
time... Mot... loc 1930z 221deg 27kt 2943 8174


Peterson

Statement as of 3:16 PM EDT on May 23, 2008

... A significant weather alert has been issued for northeastern
Marion and southeastern Putnam counties for strong winds and small
hail valid until 400 PM EDT...

At 316 PM EDT National Weather Service Doppler radar indicated a
strong thunderstorm centered 8 miles west of Salt Springs... or 8
miles southeast of Fort McCoy... moving northeast at 17 mph. This
strong thunderstorm will also affect areas around Salt Springs...
Welaka... Pomona Park... Lake Como... Georgetown and Crescent City
through 400 PM EDT. Hail up to one half inch in diameter and gusty
winds of 45 to 55 mph can be expected along with possible minor
damage.

Report damage to the nearest law enforcement agency or your County
emergency management.



Statement as of 1:17 PM EDT on May 23, 2008

... Brunswick NOAA Weather Radio transmitter is off the air...

The Brunswick transmitter wwh-39 on a frequency of 162.425 mhz is
currently off the air. Technicians are being contacted to address the
problem. Here is a list of alternative transmitters covering the
Brunswick listening area...


162.55 mhz in Jacksonville...
162.475 mhz in Waycross...
162.45 mhz in Jesup.


If i was noaa i would set up a auxillary from jacksonville at a very high power
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277. hahaguy
3:54 PM EDT on May 23, 2008
hey jp long time no see how you been?
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275. KrazyKaneLove
7:49 PM GMT on May 23, 2008
Wow , sounds serious in Broward, wpbf 25 's site is not listing any severe weather for west palm as of 5 min. ago
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273. smmcdavid
2:52 PM CDT on May 23, 2008
Hey guys, have I missed anything?
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272. IpswichWeatherCenter
7:50 PM GMT on May 23, 2008
269. HurricaneSammy 7:50 PM GMT on May 23, 2008 Hide this comment.
http://www.wptv.com/content/admin/weather/vipirradarloop.aspx

Someone Post This Image on the Blog


here u go:

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271. TerraNova
3:51 PM EDT on May 23, 2008
Upper right is Base Reflectivity.
Upper left is Storm Total Precipitation.
Lower left is Echo TOPS.
Lower right is Vertically Integrated Liquid (VIL).

The scale on the left applies to ECHO tops.

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270. hurricane23
3:50 PM EDT on May 23, 2008
Here is an 8 frame loop of the eastern atlantic low.You can pick and choose 8,16,24 frames.
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269. HurricaneSammy
7:48 PM GMT on May 23, 2008
http://www.wptv.com/content/admin/weather/vipirradarloop.aspx

Someone Post This Image on the Blog
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268. Ivansrvivr
7:46 PM GMT on May 23, 2008
50-60K tops aren't unusual in Florida during the summertime once the upper level winds lighten up later in the summer. With the strong upper level westerlies, those 55-60k tops are very impressive though.
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267. kmanislander
7:45 PM GMT on May 23, 2008
Hi everyone

The wave near 30W is rather interesting for this time of year.
Don't recall anything like this in May for many years now

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266. Patrap
2:47 PM CDT on May 23, 2008
Severe Weather Warnings Page Link
Member Since: July 3, 2005 Posts: 421 Comments: 127592
265. Patrap
2:47 PM CDT on May 23, 2008
SVR T-STORM WARNING JACKSONVILLE FL - KJAX 330 PM EDT FRI MAY 23 2008
SVR T-STORM WARNING CHEYENNE WY - KCYS 128 PM MDT FRI MAY 23 2008
SVR T-STORM WARNING NORTH PLATTE NE - KLBF 226 PM CDT FRI MAY 23 2008
SVR T-STORM WARNING GOODLAND KS - KGLD 220 PM CDT FRI MAY 23 2008
SVR T-STORM WARNING NASHVILLE TN - KOHX 218 PM CDT FRI MAY 23 2008
Member Since: July 3, 2005 Posts: 421 Comments: 127592
264. Drakoen
7:45 PM GMT on May 23, 2008
261. HurricaneSammy 7:44 PM GMT on May 23, 2008
256. Drakoen 7:41 PM GMT on May 23, 2008
Look at the echo tops on this storm cell moving in my general direction.

U Live in WPB or South


Lake Worth which is south of West Palm Beach.
Member Since: October 28, 2006 Posts: 57 Comments: 29904
263. HurricaneSammy
7:45 PM GMT on May 23, 2008
262. weatherblog 7:45 PM GMT on May 23, 2008
I'm in northern broward. We just got out of the worst of the storm thankgoodness. My neighbor's tree fell down and there's some flooding on our streets. Also we experienced some of the hail and 55-60 mph gusts here also.


Gotcha ...


One Sec ...

Getting a Good Radar
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262. weatherblog
7:39 PM GMT on May 23, 2008
I'm in northern broward here in South Florida. We just got out of the worst of the storm thankgoodness. My neighbor's tree fell down and there's some flooding on our streets. Also we experienced some of the hail and 55-60 mph gusts here also.
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261. HurricaneSammy
7:43 PM GMT on May 23, 2008
256. Drakoen 7:41 PM GMT on May 23, 2008
Look at the echo tops on this storm cell moving in my general direction.

U Live in WPB or South

" If you Live in S.Florida Press 111"

So I know who i need to help and Who to Update When They Finally Put out Warnings
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260. IpswichWeatherCenter
7:43 PM GMT on May 23, 2008
what about via NWS/NOAA Radio
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259. hahaguy
3:43 PM EDT on May 23, 2008
well it was on mine 10 mins ago
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258. HurricaneSammy
7:40 PM GMT on May 23, 2008
252. hahaguy 7:40 PM GMT on May 23, 2008
they have sammy it was on my tv


Hahaguy if they Did ....

There Should be an Emergancy Broadcast On My Tv Any minute Right Now
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257. IpswichWeatherCenter
7:40 PM GMT on May 23, 2008
250. HurricaneSammy 7:39 PM GMT on May 23, 2008
248. HurricaneGeek 7:37 PM GMT on May 23, 2008
On the Northwest part of Lake Okechobbee, there is a very strong cell! YAY!

HG don't You Agree they need to Put a Severe Watch Out?


EVEN I DO!

And to be honest I think the Nws need to move there brains out of sleepy mode and into holy monkeys Florida's about to die.
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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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