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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2357. catastropheadjuster
3:25 AM GMT on May 26, 2008
DrM has a new blog up. See you all there.
Sheri
Member Since: August 24, 2006 Posts: 21 Comments: 3653
2356. hydrus
3:22 AM GMT on May 26, 2008
PEARLANDAGGIE-I agree,all the the storms i have studied have characteristics that are unique.Not one of them is exactly the same as the other.Granted there are alot of similarities,but they have differences.
Member Since: September 27, 2007 Posts: 1 Comments: 20506
2355. Drakoen
3:11 AM GMT on May 26, 2008
Very nice Presslord.

(Jeff Masters has a new blog up)
Member Since: October 28, 2006 Posts: 57 Comments: 29887
2354. juniormeteorologist
3:11 AM GMT on May 26, 2008
Drakeon, you are intelligent, but i believe you could be a meteorologist without a degree..
2353. earthlydragonfly
3:11 AM GMT on May 26, 2008
Pearl.... Isnt that just looking at the cloud tops? I mean a young storm has its hotter layers at the top.. but as the storm builds the taller the storm gets and the clouds get cooler at the higher altitudes?? Or am I wrong thinking that way?
Member Since: July 1, 2005 Posts: 10 Comments: 1683
2352. StormJunkie
3:10 AM GMT on May 26, 2008
Dr M just posted a new blog
Member Since: August 17, 2005 Posts: 26 Comments: 15644
2351. presslord
3:10 AM GMT on May 26, 2008
What is a Meteorologist?
A Professional Guidline

A question that has been raised for a long period of time is, "What is a meteorologist?" This question has been quite common in recent years with regard to individuals referring to themselves as a "meteorologist" on television and radio. After extended discussions, the Council of the American Meteorological Society adopted on 28 September 1990, the following guideline:

A meteorologist is an individual with specialized education who uses scientific principles to explain, understand, observe or forecast the earth's atmospheric phenomena and/or how the atmosphere affects the earth and life on the planet. This specialized education would be a bachelor's or higher degree in meteorology, or atmospheric science, consistent with the requirements set forth in "The Bachelor's Degree in Meteorology or Atmospheric Science," Bulletin American Meteorological Society, 1987, Vol. 68, No. 12, p. 1570.

There are some cases where an individual has not obtained a B.S. or higher degree in meteorology, but has met the educational requirements set forth in the American Meteorological Society's Interpretive Memorandum effective June 1990, Article III, Section 4 (C), and has at least three years professional experience in meteorology. Such an individual also can be referred to as a meteorologist.

Activities of a meteorologist often are classified into a number of specialized areas. A few examples are: air pollution meteorology, global climate modeling, hydrometeorology, and numerical analysis and forecasting. These activities often require additional specialized education in related subjects.

The designation meteorologist applies to individuals who have attained the professional knowledge outlined above. Individuals who have little formal education in the atmospheric sciences, or who have taken only industry survey courses, and who disseminate weather information and forecasts prepared by others, are properly designated "weathercasters."


© 1996 American Meteorological Society
Member Since: August 13, 2007 Posts: 0 Comments: 10479
2350. moonlightcowboy
3:10 AM GMT on May 26, 2008
Have a good sleep, K'man!
Member Since: July 9, 2006 Posts: 184 Comments: 29594
2349. kmanislander
3:09 AM GMT on May 26, 2008
Anyway that's it for me for tonight. Good night all

Will chat with you tomorrow. Have a great evening.
Member Since: August 19, 2006 Posts: 0 Comments: 15725
2348. moonlightcowboy
3:08 AM GMT on May 26, 2008
2342. Thanks, K'man. Good, solid discernment imo.

Also, as I understand it, a weak NAO translates into fewer and weaker TUTTS - another plus for development. And, right now at least, our high is anchored high in the eATL, and weak on the sw periphery. I know it's early, but nearly everything indicator is pointing to potentially substantial activity.

I always enjoy your analysis, thanks!
Member Since: July 9, 2006 Posts: 184 Comments: 29594
2347. pearlandaggie
3:07 AM GMT on May 26, 2008
2341. yeah, i know...it is really cool. more disconcerting, however, is our lack of knowledge of these storms and how forecasters consistently prematurely predict the degradation of these storms. the figure below is a time series of hurricane Luis to an annular hurricane. notice how the IR profile warms, but becomes more uniform...almost suggesting an increased efficiency within the storm which may partly explain the longevity and stamina of these storms...


Member Since: September 14, 2007 Posts: 3 Comments: 3963
2346. Drakoen
3:07 AM GMT on May 26, 2008
2344. juniormeteorologist 3:04 AM GMT on May 26, 2008
Drakeon, I was not talking about people with a degree! I truly believe that anybody can be a meteorologist if you know how to predict weather or real forecast models...and etc. Maybe you may consider the offer.


Of course; you can take something like the NWA test or become and AMS member and be considered a meteorologist. If I wanted to be a meteorologist I would probably get my bachelors and masters degree at a university.
Member Since: October 28, 2006 Posts: 57 Comments: 29887
2345. Stormchaser2007
3:06 AM GMT on May 26, 2008
Oh dang Junior Drak is as good is as they get...well anyway Im going to watch the news so see yall later.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
2344. juniormeteorologist
3:04 AM GMT on May 26, 2008
Drakeon, I was not talking about people with a degree! I truly believe that anybody can be a meteorologist if you know how to predict weather or real forecast models...and etc. Maybe you may consider the offer.
2343. pearlandaggie
3:03 AM GMT on May 26, 2008
IR images of annular hurricanes...

Member Since: September 14, 2007 Posts: 3 Comments: 3963
2342. kmanislander
3:03 AM GMT on May 26, 2008
Sorry folks my internet went out for a few minutes.

MLC, you asked about the twaves coming off the W African coast. All things being equal a high frequency of potent waves would result in an active CV season, all other things being equal.

However, in years with high shear or lots of dust we have seen wave after wave get either torn apart or just not develop.

2004 was a slow starter and then like someone throwing a switch we had an 8 to 10 week stretch of storm after storm. Some seasons have clearly defined periods of either lots of activity, no acivity or a mix.

The June/July period is too early as an indicator based on what we have seen in the past but if shear is light this year combined with low dust and neutral conditions then those Twaves could very well produce a busy CV season.

Of course, whether they come in low through the Caribbean or recurve early we will just have to wait and see how the Bermuda high sets up as well as whether the troughs swing low across the Eastern seaboard
Member Since: August 19, 2006 Posts: 0 Comments: 15725
2341. hydrus
3:02 AM GMT on May 26, 2008
PEARLANDAGGIE-I saw a program on the tube that showed Isabel actually began as a low pressure area near the red sea,they had a satellite movie of the entire life of the storm from start to finish.It is really cool how far this technology has come since it began.
Member Since: September 27, 2007 Posts: 1 Comments: 20506
2340. pearlandaggie
3:00 AM GMT on May 26, 2008
wind profiles from annular hurricanes...notice the relatively constant velocity profile from top to bottom...

Member Since: September 14, 2007 Posts: 3 Comments: 3963
2339. Drakoen
3:00 AM GMT on May 26, 2008
2330. Bamatracker 2:53 AM GMT on May 26, 2008
2324. juniormeteorologist 2:50 AM GMT on May 26, 2008
CaneAddict I just emailed you..Also if anyone will like to be an online meteorologist, just email me at admin@dthgamer.com with the subject Meteorologist!

Technically everyone one here are meteorologist. Anybody who takes an interest in weather can be considered a meteorologist. Never have to forecast a thing!!


Probably talking about people with degrees.
Member Since: October 28, 2006 Posts: 57 Comments: 29887
2338. Drakoen
2:59 AM GMT on May 26, 2008
The global computer model guidance suggest the Caribbean will moisten up in 3 days especially in the south.
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2337. Stormchaser2007
2:56 AM GMT on May 26, 2008
I'm out see y'all tomorrow!!!
Member Since: June 9, 2007 Posts: 4 Comments: 15776
2336. moonlightcowboy
2:56 AM GMT on May 26, 2008
Have a good sleep, Chaser, JLPR and 456! Thanks for the holiday wishes. My youngest grads high school tomorrow, too. Enjoyed the tropical discussion today.
Member Since: July 9, 2006 Posts: 184 Comments: 29594
2335. Stormchaser2007
2:55 AM GMT on May 26, 2008
See ya tomorrow JLPR.
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2334. Cavin Rawlins
2:54 AM GMT on May 26, 2008
One thing before I go....I looked at a 24 hr loop of West Africa and I appears the area of convection along the coast is a tropical wave based on the westward propagation of convective signiture. I will confirm this wen i update my blog in the morn. have a good night all and happy memorial day to yall in the US of A. Also, the area showers of the EPAC should be of interest over the next couple of days. This appears to be the time to start looking for signs of possible advection into Central America or the Caribbean Sea.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2333. pearlandaggie
2:54 AM GMT on May 26, 2008
interesting paper on annular hurricanes...

Link
Member Since: September 14, 2007 Posts: 3 Comments: 3963
2332. JLPR
2:54 AM GMT on May 26, 2008
Well im out =)
till tomorrow =)
good night everyone
Member Since: September 4, 2007 Posts: 36 Comments: 5223
2331. Stormchaser2007
2:54 AM GMT on May 26, 2008
Well heres the Caribbean TCHP animated.

Member Since: June 9, 2007 Posts: 4 Comments: 15776
2330. Bamatracker
2:53 AM GMT on May 26, 2008
2324. juniormeteorologist 2:50 AM GMT on May 26, 2008
CaneAddict I just emailed you..Also if anyone will like to be an online meteorologist, just email me at admin@dthgamer.com with the subject Meteorologist!


Technically everyone one here are meteorologist. Anybody who takes an interest in weather can be considered a meteorologist. Never have to forecast a thing!!

Member Since: May 17, 2006 Posts: 6 Comments: 1367
2329. Stormchaser2007
2:52 AM GMT on May 26, 2008
Yeah I think that might be one of the few things that do it besides winter storms.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
2328. moonlightcowboy
2:52 AM GMT on May 26, 2008


TCHP, indeed, expanding.
Member Since: July 9, 2006 Posts: 184 Comments: 29594
2327. Stormchaser2007
2:51 AM GMT on May 26, 2008
Yeah pearl!! Nice to know junior.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
2326. Bamatracker
2:51 AM GMT on May 26, 2008
2323. Stormchaser2007 2:50 AM GMT on May 26, 2008
Aw everyones gone.....


yea pinwheel eyes tend to do that!!!

Member Since: May 17, 2006 Posts: 6 Comments: 1367
2325. pearlandaggie
2:50 AM GMT on May 26, 2008
2322. THANK GOD! :)
Member Since: September 14, 2007 Posts: 3 Comments: 3963
2324. juniormeteorologist
2:50 AM GMT on May 26, 2008
CaneAddict I just emailed you..Also if anyone will like to be an online meteorologist, just email me at admin@dthgamer.com with the subject Meteorologist!
2323. Stormchaser2007
2:50 AM GMT on May 26, 2008
Aw everyones gone.....
Member Since: June 9, 2007 Posts: 4 Comments: 15776
2322. Stormchaser2007
2:49 AM GMT on May 26, 2008
Yeah thats the Pinwheel eye effect....haven't seen that in a while.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
2321. HurricaneGeek
2:47 AM GMT on May 26, 2008
good evening everybody
Member Since: May 10, 2007 Posts: 110 Comments: 7039
2320. pearlandaggie
2:45 AM GMT on May 26, 2008
cool inner-eye cloud structure

Member Since: September 14, 2007 Posts: 3 Comments: 3963
2319. Stormchaser2007
2:45 AM GMT on May 26, 2008
Welcome Pearl! : )
Member Since: June 9, 2007 Posts: 4 Comments: 15776
2318. Stormchaser2007
2:45 AM GMT on May 26, 2008
NHC made me laugh with every advisory on that one .
Member Since: June 9, 2007 Posts: 4 Comments: 15776
2317. pearlandaggie
2:43 AM GMT on May 26, 2008
aaaaaaaaaaaawwwwwwwwwwww yeah! thanks, StormChaser!

the lack of knowledge of annular storms and their longevity is startling even to this day!
Member Since: September 14, 2007 Posts: 3 Comments: 3963
2316. CaneAddict
2:43 AM GMT on May 26, 2008

2308. juniormeteorologist 2:39 AM GMT on May 26, 2008
CaneAddict thanx for the comment on the picture! anyway, i am about to work on my website. Will you like to an meteorologist for my website?


Link...please and mail me regarding the meterologist part..

Member Since: October 5, 2007 Posts: 3 Comments: 2151
2315. Stormchaser2007
2:43 AM GMT on May 26, 2008
See you Cane have a good night.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
2314. moonlightcowboy
2:42 AM GMT on May 26, 2008
K'man, another thing - 456 and I have noticed an earlier movement, frequency and surprisingly organized twaves off Africa already, suggesting that we may seem some earlier CV storms develop. Thoughts?
Member Since: July 9, 2006 Posts: 184 Comments: 29594
2313. Chicklit
2:42 AM GMT on May 26, 2008
Anyway, night all ... Glad to be here.
Member Since: July 11, 2006 Posts: 14 Comments: 11174
2312. CaneAddict
2:42 AM GMT on May 26, 2008
Folks i am off for the night, Have a great Memorial Day! night.
Member Since: October 5, 2007 Posts: 3 Comments: 2151
2311. Stormchaser2007
2:41 AM GMT on May 26, 2008
Hurricane Epsilon
Member Since: June 9, 2007 Posts: 4 Comments: 15776
2310. pearlandaggie
2:41 AM GMT on May 26, 2008
2305. sgreed. i just find it interesting that with today's computer power, it is probably the lack of understanding of atmospheric dynamics that drives uncertainty...AND it takes HOURS to crunch the data with TODAY'S computers!

one would think NOAA would try to use civilian computing power....something along the lines of what SETI is doing....just a thought!
Member Since: September 14, 2007 Posts: 3 Comments: 3963
2309. aspectre
2:40 AM GMT on May 26, 2008
2233. StormJunkie "...where you scooping those pics from?

http://phoenix.lpl.arizona.edu/ or more specificly for thumbnail links to larger images from the Phoenix.
Member Since: August 21, 2007 Posts: 0 Comments: 4860
2308. juniormeteorologist
2:39 AM GMT on May 26, 2008
CaneAddict thanx for the comment on the picture! anyway, i am about to work on my website. Will you like to an meteorologist for my website?
2307. Chicklit
2:39 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.
Member Since: July 11, 2006 Posts: 14 Comments: 11174

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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.