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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2001. stormhank 22:57 GMT le 25 mai 2008
Hey Drak n SJ.. I just got home from work...whats latest on potential GFS system?? Member Since: 8 septembre 2005 Posts: 0 Comments: 1375

2002. IKE 22:58 GMT le 25 mai 2008
lol. Member Since: 9 juin 2005 Posts: 23 Comments: 37047

2003. JLPR 22:58 GMT le 25 mai 2008
I see there isn't anything new in the tropics but apparently the models want to develop something right on the start of the season we will just have to wait and see =) and Hello everyone =) Member Since: 4 septembre 2007 Posts: 36 Comments: 5223

2004. nash28 22:58 GMT le 25 mai 2008
Actually Ike, probably not.. Why??? The early track runs are usually 100's of miles off:-) Trust me, I've learned that lesson plenty here:-) Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

2006. weathersp 22:59 GMT le 25 mai 2008
Intresting that the 12z GFS and now the 18z GFS now agree with the NOGAPS.. Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

2007. Stormchaser2007 22:59 GMT le 25 mai 2008
Drak, Never mind it was stupid of me to try and ask something personal like that. Im sorry.... Member Since: 9 juin 2007 Posts: 4 Comments: 15249

2008. IKE 23:00 GMT le 25 mai 2008
Look at the NHC website...June tracks on average... Member Since: 9 juin 2005 Posts: 23 Comments: 37047

2009. stormhank 23:00 GMT le 25 mai 2008
Hey JP! how u been bro? Whats your take on the GFS potentil carribean developement? Member Since: 8 septembre 2005 Posts: 0 Comments: 1375

2010. JLPR 23:00 GMT le 25 mai 2008
yeah tracks sure change a lot I remember one track that collocated Dean right in top of me I went to panic mode lol then the track shifted south lol =P then I went back to normal mode =D Member Since: 4 septembre 2007 Posts: 36 Comments: 5223

2011. Drakoen 23:00 GMT le 25 mai 2008
Nash I see movement lol. The steering current could be weak enough to keep it down there meandering. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

2012. TampaSpin 23:02 GMT le 25 mai 2008
I see alittle spin in the SWCarrib.......lol Member Since: 2 septembre 2007 Posts: 175 Comments: 19747

2014. TampaSpin 23:03 GMT le 25 mai 2008
How you ghost seekers doing...lol Member Since: 2 septembre 2007 Posts: 175 Comments: 19747

2015. stormhank 23:03 GMT le 25 mai 2008
are u doing the hurricane contest this year? Member Since: 8 septembre 2005 Posts: 0 Comments: 1375

2017. nash28 23:04 GMT le 25 mai 2008
Drak, I understand buddy. What I am saying is we've gome from Miami, to Tampa, to poof, to Texas and now to the Panhandle. It will change again:-) Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

2018. kingy 23:04 GMT le 25 mai 2008
I still think it is too early to have confidence in models that are more than a few days out. The season is but young.

2019. Patrap 23:05 GMT le 25 mai 2008
UNYSIS GFSx 2JUNE 0Z surface Link Member Since: 3 juillet 2005 Posts: 372 Comments: 111641

2020. nash28 23:07 GMT le 25 mai 2008
And..... My chase may be on earlier than I expected... Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

2021. TampaSpin 23:07 GMT le 25 mai 2008
Gang i do see some moisture has entered the area that development in the SWCarrb. system is hinted to take place. Member Since: 2 septembre 2007 Posts: 175 Comments: 19747

2022. kingy 23:09 GMT le 25 mai 2008
interesting link Patrap ! CCHSweatherman - may I ask what do you make of this? I am looking forward to the next week on this blog, especially Dr Masters views on the emerging data and models.

2023. Drakoen 23:09 GMT le 25 mai 2008
2005. jphurricane2006 10:59 PM GMT on May 25, 2008 From what I have seen, there are a ton of storms that have stalled in that area before right. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

2024. JLPR 23:10 GMT le 25 mai 2008
I was thinking thats it amazing that Puerto Rico being located right in the middle of the ocean hasn't have a hurricane hit since Georges 1998. 10 years!! well almost 10 still a few months to go before the 10th anniversary of Georges =P Member Since: 4 septembre 2007 Posts: 36 Comments: 5223

2025. weathersp 23:10 GMT le 25 mai 2008
I didn't think we would get any sort of action till Mid-July.. Lets see if Nature will really prove me wrong. Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

2026. nash28 23:12 GMT le 25 mai 2008
Look.. I am ALL FOR A STALL so long as it is a wet system that brings moisture to the area. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

2027. Patrap 23:12 GMT le 25 mai 2008
The trends in the tropical Models shows us that the climatological favored areas are beginning to rumble...awaken if you will Member Since: 3 juillet 2005 Posts: 372 Comments: 111641

2028. nash28 23:13 GMT le 25 mai 2008
Yeah, they are Pat. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

2029. moonlightcowboy 23:14 GMT le 25 mai 2008
sp, I think you may be right. Climatology wise we could see something out of the Carib/GOM - lots of dry present (at least yesterday); but, I'm a bit more concerned about the decent waves, frequency already coming from CV. We may see a bit of an earlier start with these systems than normal. But, shoot, I certainly don't know - just the overall take from the last three or four weeks here discussing all of it. Member Since: 9 juillet 2006 Posts: 179 Comments: 28123

2030. cchsweatherman 23:14 GMT le 25 mai 2008
2022. kingy 7:09 PM EDT on May 25, 2008 interesting link Patrap ! CCHSweatherman - may I ask what do you make of this? I am looking forward to the next week on this blog, especially Dr Masters views on the emerging data and models. Feel free to ask me questions kingy. To answer your question, it just seems odd that the GFS stalls the storm over the southern Gulf of Mexico. With an obvious weakness in the ridge presented in the GFS model, there should be movement. Right now, I feel quite confident in saying there will be a developing tropical system off the Yucatan Peninsula late week, but am not confident beyond that. It gets too complex after the point the system reaches the Yucatan area. Member Since: 14 avril 2007 Posts: 8 Comments: 4926

2031. nash28 23:15 GMT le 25 mai 2008
Great points MLC! I firmly believe we will have a busier beginning of the season. Hopefully, nothing like 2004 or 2005. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

2032. weathersp 23:17 GMT le 25 mai 2008
Well once you get into the GOM.. theres only 2 ways out..and you usually can't go out the way you go in.. Both are about only 90 Miles across! Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

2033. TampaSpin 23:17 GMT le 25 mai 2008
Looking at Water Vapor it appears a trough is near Jamacia. Could it be that a Surface low will develop from this trough in the Western Carribean. Just a thought of observation if im seeing this correct. Member Since: 2 septembre 2007 Posts: 175 Comments: 19747

2034. kingy 23:19 GMT le 25 mai 2008
Many thanks CCHS

2035. hurricane23 23:20 GMT le 25 mai 2008
2031. nash28 7:15 PM EDT on May 25, 2008 Great points MLC! I firmly believe we will have a busier beginning of the season. Hopefully, nothing like 2004 or 2005. Busier probably so andy but the all important issue as always is were will they all strike. Member Since: 14 mai 2006 Posts: 8 Comments: 13279

2036. Patrap 23:20 GMT le 25 mai 2008
Next Event is Cruise Stage separation at 7:39:17 EST Link Member Since: 3 juillet 2005 Posts: 372 Comments: 111641

2037. StormJunkie 23:26 GMT le 25 mai 2008
Nasa TV Live Phoenix coverage Member Since: 17 août 2005 Posts: 26 Comments: 15218

2038. moonlightcowboy 23:26 GMT le 25 mai 2008
...bloghole. Hope WUdevelopers get these blog kinks worked out before things start popping. Member Since: 9 juillet 2006 Posts: 179 Comments: 28123

2039. Patrap 23:27 GMT le 25 mai 2008
4:18 pm PDT NASA Blog Link We've now confirmed completion of the successful pressurization of the descent engines. This is a critical event that is now behind us. We're expecting cruise stage separation in less than twenty minutes. Member Since: 3 juillet 2005 Posts: 372 Comments: 111641

2040. Drakoen 23:27 GMT le 25 mai 2008
I'm waiting for the next cyclone that beats Tip in pressure lmao! Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

2041. moonlightcowboy 23:30 GMT le 25 mai 2008
Drakoen posted a NOGAPS shot earlier today that showed a westerly expanded high across the Atl. Another showed it stronger, but anchored out in the upper eATL, but dipping sw'ly and weaker around the periphery. Member Since: 9 juillet 2006 Posts: 179 Comments: 28123

2042. Drakoen 23:30 GMT le 25 mai 2008
The 18z NOGAPS is interesting favoring a more easterly course. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

2043. hurricane23 23:30 GMT le 25 mai 2008
2040. Drakoen 7:27 PM EDT on May 25, 2008 I'm waiting for the next cyclone that beats Tip in pressure lmao! Might have to wait a while for that.Wilma had a pretty good shot at that but did not quite make it.Conditions that were around with wilma are some you dont see very often.The conditions were favorable in almost every level you can think of. Member Since: 14 mai 2006 Posts: 8 Comments: 13279

2044. IKE 23:32 GMT le 25 mai 2008
Here's the 18Z NOGAPS.... Link Member Since: 9 juin 2005 Posts: 23 Comments: 37047

2045. cchsweatherman 23:32 GMT le 25 mai 2008
2042. Drakoen 7:30 PM EDT on May 25, 2008 The 18z NOGAPS is interesting favoring a more easterly course. Link please? Member Since: 14 avril 2007 Posts: 8 Comments: 4926

2046. franck 23:32 GMT le 25 mai 2008
2033...looks mighty dry for storm development. Member Since: 30 août 2005 Posts: 0 Comments: 1150

2047. hurricane23 23:33 GMT le 25 mai 2008
Miami is likely to finish may below average as far as precip goes what might all that mean come this hurricane season is yet to be seen. Member Since: 14 mai 2006 Posts: 8 Comments: 13279

2048. Drakoen 23:33 GMT le 25 mai 2008
2043. hurricane23 11:30 PM GMT on May 25, 2008 2040. Drakoen 7:27 PM EDT on May 25, 2008 I'm waiting for the next cyclone that beats Tip in pressure lmao! Might have to wait a while for that.Wilma had a pretty good shot at that but did not quite make it.Conditions that were around with wilma are some you dont see very often.The conditions were favorable in almost every level you can think of. Yea. I'm interested to see what the major hurricanes look like this year. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

2049. Drakoen 23:34 GMT le 25 mai 2008
2045. cchsweatherman 11:32 PM GMT on May 25, 2008 2042. Drakoen 7:30 PM EDT on May 25, 2008 The 18z NOGAPS is interesting favoring a more easterly course. Link please? Its above you lol. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

2050. StormJunkie 23:36 GMT le 25 mai 2008
T - 15 min 30 sec Member Since: 17 août 2005 Posts: 26 Comments: 15218

2051. Drakoen 23:37 GMT le 25 mai 2008
Super Typhoon Gay got close to Tip. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

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