Dr. Jeff Masters' WunderBlog

Mile-wide tornado smashes Windsor, Colorado; plus, hurricane season commentary

Posted by: Dr. Jeff Masters, 13:23 GMT le 23 mai 2008

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

Tornado Damage 3 (jlg)

Damage from today's Tornado in Windsor, Colorado

()

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

Categories: Tornado

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1901. Drakoen 21:09 GMT le 25 mai 2008
1900. FLWeatherFreak91 9:07 PM GMT on May 25, 2008 The GFS should be finished before 6, am I correct? Yes if you mean am and not pm. In the 18z run it reaches 144hr at 6:30pm. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

1902. cdo 21:11 GMT le 25 mai 2008
wow, it is set to average.... Why do sepeate people basically post the same thing like 10 billion times here? Member Since: 26 août 2006 Posts: 0 Comments: 7

1903. aspectre 21:17 GMT le 25 mai 2008
1717. scottsvb "...your getting mostly the wrong info...these are mostly...wishcasters..." 1754. CaneAddict "...a few that so called "wish cast"...only come around when a category 5 is heading to Europe but they want it to come to Atlanta Georgia..." You must have missed NASA's photo of the Cat.8 approaching landfall in Miami... ...and Melbourne and Moscow and Mumbai and... Member Since: 21 août 2007 Posts: 0 Comments: 4846

1904. presslord 21:19 GMT le 25 mai 2008
aspectre....I think I see a pinhole eye.... Member Since: 13 août 2007 Posts: 0 Comments: 10377

1905. StormJunkie 21:26 GMT le 25 mai 2008
1894. There is only one that carves the tablets in stone, and that forecaster, or comedy show, is no longer among us here on the blogs :~) Member Since: 17 août 2005 Posts: 26 Comments: 15218

1906. Bamatracker 21:28 GMT le 25 mai 2008
should we take a moment of silence SJ? Member Since: 17 mai 2006 Posts: 6 Comments: 1364

1907. Drakoen 21:29 GMT le 25 mai 2008
1905. StormJunkie 9:26 PM GMT on May 25, 2008 1894. There is only one that carves the tablets in stone, and that forecaster, or comedy show, is no longer among us here on the blogs :~) lol I know who you are talking about! Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

1908. nash28 21:31 GMT le 25 mai 2008
MMMMMMMM...... Biting lips.... This year gonna have to modify the aclown comment to fit with the Admin rules:-) Member Since: 11 juillet 2005 Posts: 190 Comments:** 16972

1909. Bamatracker 21:32 GMT le 25 mai 2008
ahh...moment of silence over...those were the days.... Member Since: 17 mai 2006 Posts: 6 Comments: 1364

1910. TexasGulf 21:32 GMT le 25 mai 2008
People seem to be impatient for the Gulf & Carribean tropical season's conditions to become set up. I haven't posted anything about the ghost echo of a storm that may or may not form into something 5-days from now. Conditions aren't ripe yet to produce anything of any significance. If something does form in the Gulf during the next week, prevailing patterns will quickly move it inland. It won't have time to stall or grow. Based on conditions, I think we are in for an active Atlantic and Carribean season. Anything getting into the Gulf will probably move into the Northern Gulf due to the high position of the jet stream this year. Some years do get an early start. Conditions are becoming better organized, but we aren't at the point of concern yet for a significant storm. Member Since: 28 avril 2008 Posts: 0 Comments: 354

1911. StormJunkie 21:33 GMT le 25 mai 2008
lol BT, not sure. I occasionally find myself missing him for some odd reason. Was very good at breaking up any clash of personalities between bloggers! Nothing like one of his tirades to get all of us back on the same page! Member Since: 17 août 2005 Posts: 26 Comments: 15218

1912. StormJunkie 21:34 GMT le 25 mai 2008
1908, it finally got brought out! Been waiting for you to say it nash, knew it was coming sooner or later! Member Since: 17 août 2005 Posts: 26 Comments: 15218

1913. nash28 21:35 GMT le 25 mai 2008
Yeah SJ. But I even censored myself with it... Oh God. I'm getting soft!!!! Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1914. Bamatracker 21:35 GMT le 25 mai 2008
lol sj!! Member Since: 17 mai 2006 Posts: 6 Comments: 1364

1915. nash28 21:35 GMT le 25 mai 2008
Ok. Gotta run to the liquor store. Need Bourbon for the salmon I'm going to grill. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1916. weathersp 21:40 GMT le 25 mai 2008
Send the leftovers will ya nash! Thanks! Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

1917. moonlightcowboy 21:41 GMT le 25 mai 2008
LOL, sp - the salmon leftovers? ; P Member Since: 9 juillet 2006 Posts: 179 Comments: 28117

1918. Drakoen 21:48 GMT le 25 mai 2008
1917. moonlightcowboy 9:41 PM GMT on May 25, 2008 LOL, sp - the salmon leftovers? ; P must be ;P Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

1919. StormJunkie 21:49 GMT le 25 mai 2008
Memorial Day Weekend USS Yorktown parked in Charleston Harbor with the new Arthur Ravenel Bridge in the background. Member Since: 17 août 2005 Posts: 26 Comments: 15218

1920. Bamatracker 21:49 GMT le 25 mai 2008
ok...ive had a severe thundstorm pop up in the next county, now one has popped up literally 3 miles south of my house....and the sun is out here....what do I have to do to get some rain!!! Member Since: 17 mai 2006 Posts: 6 Comments: 1364

1921. hurricane23 21:50 GMT le 25 mai 2008
Good afternoon! I see models are still all over the place with development E pac/caribbean.Here is something though i think is worth mentioning and is a graphic i use during tropical cyclone season. Dark blue means upward motion which is needed for tc formation.Notice into next week as some upward motion trys to make its way into the caribbean come may31-june9.There are other mjo graphics which you can use but i tend to use this one often. Hope everyone is having a great labor day weekend. Adrian Member Since: 14 mai 2006 Posts: 8 Comments: 13274

1922. Cavin Rawlins 22:00 GMT le 25 mai 2008
The GFS is out to 72 hrs, but dont have to look much further than 42 hrs to see the precursor of the forecasted disturbance. http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/carib/gfs/18/model_s.shtml Member Since: 24 juillet 2005 Posts: 407 Comments: 19076

1923. presslord 22:00 GMT le 25 mai 2008
nice pic sj...Memorial Day note: the Yorktown houses the Medal of Honor Museum..... Member Since: 13 août 2007 Posts: 0 Comments: 10377

1924. Patrap 22:00 GMT le 25 mai 2008
40 Minutes now to Cruise stage separation. The Entry Sequence is about to begin.Link Member Since: 3 juillet 2005 Posts: 370 Comments: 111244

1925. Baybuddy 22:02 GMT le 25 mai 2008
We can't say stormtop? What is he like Voldemort or something? Member Since: 26 juin 2006 Posts: 0 Comments: 1115

1926. Patrap 22:03 GMT le 25 mai 2008
Just dont say it 3 Times in a row and then say BAMM,(medium) You could rip the Blog space time continuum. Member Since: 3 juillet 2005 Posts: 370 Comments: 111244

1927. Baybuddy 22:04 GMT le 25 mai 2008
Ha!!!! Member Since: 26 juin 2006 Posts: 0 Comments: 1115

1928. presslord 22:05 GMT le 25 mai 2008
Are we allowed to say 'tunnells'? Member Since: 13 août 2007 Posts: 0 Comments: 10377

1929. StormJunkie 22:07 GMT le 25 mai 2008
Thanks press, just wish I had a little more sun on my side of the boat. It was a great day to stroll the docks and talk to the many folks just hanging on there boats. pat, Nasa TV already has the feed up, but no audio that I can tell? Uhhh, ok, guess they are trying to work out some audio issues now, should be up soon. Member Since: 17 août 2005 Posts: 26 Comments: 15218

1930. StormJunkie 22:07 GMT le 25 mai 2008
lol Bay :~) Member Since: 17 août 2005 Posts: 26 Comments: 15218

1931. Baybuddy 22:08 GMT le 25 mai 2008
NO!!!!! Please, no tunnels.....whimper whimper... I'll do anything. Member Since: 26 juin 2006 Posts: 0 Comments: 1115

1932. moonlightcowboy 22:09 GMT le 25 mai 2008
Audio here, SJ; but, it does sound like they're having some difficulties, and Pat can correct me here, too, it seems that sometimes it's intermittent intentionally until the event is closer. Member Since: 9 juillet 2006 Posts: 179 Comments: 28117

1933. StormJunkie 22:11 GMT le 25 mai 2008
Thanks mlc, just heard that right after I posted. Afternoon to ya! Good to see you as well Bay. Member Since: 17 août 2005 Posts: 26 Comments: 15218

1934. weathersp 22:12 GMT le 25 mai 2008
NASA TV Now broadcasting live feed from Phoenix Control Center. Note: This link will launch a separate Windows Media Player window. Phoenix Mars Polar lander Control Room Video Feed Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

1935. Patrap 22:12 GMT le 25 mai 2008
I think probably someone is stepping on a cable somewhere in Australia at the Canberra Dish. Member Since: 3 juillet 2005 Posts: 370 Comments: 111244

1936. Baybuddy 22:13 GMT le 25 mai 2008
Ditto SJ! Member Since: 26 juin 2006 Posts: 0 Comments: 1115

1937. Patrap 22:15 GMT le 25 mai 2008
audio intermittent at best here. I can hear the ISS yelling down from orbit better Member Since: 3 juillet 2005 Posts: 370 Comments: 111244

1938. Patrap 22:16 GMT le 25 mai 2008
Well thats better ,,thanks eccom Member Since: 3 juillet 2005 Posts: 370 Comments: 111244

1939. StormJunkie 22:16 GMT le 25 mai 2008
lol pat... GFS out to 114 now Member Since: 17 août 2005 Posts: 26 Comments: 15218

1940. moonlightcowboy 22:16 GMT le 25 mai 2008
Yep, sounding much better now. Member Since: 9 juillet 2006 Posts: 179 Comments: 28117

1941. surfmom 22:16 GMT le 25 mai 2008
Hey patrap & co., thanks for the nasa links my son is stoked watching this stuff. Member Since: 18 juillet 2007 Posts: 30 Comments: 26538

1942. Patrap 22:17 GMT le 25 mai 2008
from the NASA Blog Link 2:45 pm PDT We are now two hours out from EDL. The team has assembled in Mission Control, from where I'm now blogging. Everyone is excited and nervous as the spacecraft nears Mars. All the final uploads have been made and we are now along for the ride as five years of hard work reaches its climax. The project manager is making his way through Mission Control wishing everyone luck as we ready ourselves for EDL. Stay tuned for updates. Member Since: 3 juillet 2005 Posts: 370 Comments: 111244

1943. Stormchaser2007 22:17 GMT le 25 mai 2008
Well here we go again..... Member Since: 9 juin 2007 Posts: 4 Comments: 15243

1944. cchsweatherman 22:18 GMT le 25 mai 2008
The 18UTC GFS model 126 hours has the Western Caribbean storm off the Yucatan Peninsula in 126 hours (by Friday). Member Since: 14 avril 2007 Posts: 8 Comments: 4926

1945. Drakoen 22:22 GMT le 25 mai 2008
Yea the GFS still has development just where will it go with the system... Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

1946. surfmom 22:25 GMT le 25 mai 2008
Surf rumour: waves from the Yucatan channel to the gomex June 1 - does this make sense to you guys? Member Since: 18 juillet 2007 Posts: 30 Comments: 26538

1947. weathersp 22:25 GMT le 25 mai 2008
18z looks like it has the system much weaker than previous runs. Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

1948. IKE 22:27 GMT le 25 mai 2008
It's the same strength as 144 hours on the previous(12Z), run. 1008 mb's....at 138 hours on this run. Member Since: 9 juin 2005 Posts: 23 Comments: 37044

1949. Drakoen 22:28 GMT le 25 mai 2008
It looks like it wants the system to go into the BOC looking at that low level ridge in the Gulf. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

1951. weathersp 22:30 GMT le 25 mai 2008
BOC = Bay of Campeche? Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

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