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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157. NEwxguy
5:42 PM GMT on May 23, 2008
severe th strm warning around boca raton

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156. katadman
5:47 PM GMT on May 23, 2008
Afternoon, all.
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155. Ivansrvivr
5:39 PM GMT on May 23, 2008
150. With the Bermuda high looking like it may be quite weak, low riding storms like the current one in the E.ATL below 10N would be biggest threat for Florida and Gulf Coast. Unlike last season when everything in the Caribbean went due west, the opposite looks likely this year. Anything moving north of the Antilles looks like it will be biggest threat to Carolinas northward.
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154. bystander
5:36 PM GMT on May 23, 2008
Usually don't say much. Just want to wish everyone a safe and happy memorial day weekend.
Thanks to all for all of the helpful information in here.
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153. atmoaggie
5:34 PM GMT on May 23, 2008
I live in Attascocita near Kingwood

Small world. Drove through your area all the time. Nederland (In-laws) to Kings River. The only intelligent way to get there is to take US90 through Liberty/Dayton/ 1960 to Atascocita.

I hear you about the Ins companies. My issue is a little different. I still cannot get Liberty-Mutual to write a policy in Covington, LA because it is in St. Tammany Parish. News flash: Parts of St. Tammany are over 100 feet above sea level! My house at about 40 feet above sea level, did not flood during Katrina (10 miles away from it), had no damage from Katrina, had no water from 1 foot of rain in 24 hours last year, had no water from 4.5 inches in 1 hour last week. (Matter of fact: not even standing water in the yard or street...I am on the top of a miles-wide hill)

Those theives could make so much more money if they would only hire a geographer to evaluate potential new policies.
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152. Weather456
1:38 PM AST on May 23, 2008
149. mississippiwx23 1:37 PM AST on May 23, 2008
The GFS is producing two lows out of one area of disturbed weather, which is a common error in the GFS. I would not be surprised to see all of the energy condense into one low in the eastern pacific.


I know its a little too early to tell which side will be taken. But the current infrared imagery shows much of the shower and thunderstorm activity in the Eastern Pac. It may or may not be this area but time will answer all questions.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
151. Ivansrvivr
5:37 PM GMT on May 23, 2008
The only way both systems would develop if the E-Pac system stayed small and moved quickly westward. I doubt that will be the case.
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150. moonlightcowboy
12:36 PM CDT on May 23, 2008
556. StormW 7:25 AM CDT on May 23, 2008
548. moonlightcowboy 8:01 AM EDT on May 23, 2008
StormW, if the wave at 27w continues to run low as it is now, couldn't it slip in under the TUTT (looks to lifting out to the ne) as it moves west?


It's a possibility...however there is a lot of dry air ahead of it. As far as recurvature, forecast steering indicates unless this were to become fairly strong, it would be a straight shot to the islands before any recurvature took place.



...I see it has a low designated with it now, too. Yeah, with the way these waves have been coming off early, now, the cv season looks like it could be trouble.

Member Since: July 9, 2006 Posts: 184 Comments: 29610
149. mississippiwx23
5:34 PM GMT on May 23, 2008
The GFS is producing two lows out of one area of disturbed weather, which is a common error in the GFS. I would not be surprised to see all of the energy condense into one low in the eastern pacific.
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148. Ivansrvivr
5:34 PM GMT on May 23, 2008
Dont feel bad A.T.,my ADD took over years ago.
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147. Weather456
1:33 PM AST on May 23, 2008
143. IKE 1:31 PM AST on May 23, 2008
109. cchsweatherman 12:03 PM CDT on May 23, 2008
103. IKE 12:49 PM EDT on May 23, 2008
GFS develops an EAST PAC + a Caribbean system....unusual...

In my opinion, the GFS has dropped the Caribbean system and only shows a strong Eastern Pacific storm. The GFS just shows some intense tropical rains over South and Central Florida for several days starting June 2nd.

Drops it? Not what I see.


LINK Still there
Member Since: July 24, 2005 Posts: 407 Comments: 19076
146. waverunner
5:32 PM GMT on May 23, 2008
Hello everyone, just wanted to let you all know that I enjoy reading your comments. Hope we don't have destructive canes this year.
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145. atmoaggie
5:33 PM GMT on May 23, 2008
Don't feel bad cchs, my ADD took over after percieved sentance number 4. Couldn't finish it...
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144. retaining1
5:25 PM GMT on May 23, 2008
135. atmoaggie

I live in Attascocita near Kingwood. My house is 72 feet above sea level with great drainage and we are about 70 miles inland from Galveston Bay.

Still, several insurance companies refused to write homeowners policies for my house. Among them were Progressive and State Farm and Farmers.

I said, Oh so you're not covering homes in Harris County (Houston) then. They said no, just your zip code. It's due to that Summerwood subdivision being built at Belt-8 & West Lake Houston being so low lying. They are building $200-$300,000 homes in a known flood plain, then people are suprised when they flood. Since we are located in same zip code, insurance lumps all together in one category.

LOL; they cover homes in Baytown and Channelview 10-feet above sea level near the coast, but won't cover homes 70 miles inland at a 72 foot elevation. Go figure.
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143. IKE
12:30 PM CDT on May 23, 2008
109. cchsweatherman 12:03 PM CDT on May 23, 2008
103. IKE 12:49 PM EDT on May 23, 2008
GFS develops an EAST PAC + a Caribbean system....unusual...

In my opinion, the GFS has dropped the Caribbean system and only shows a strong Eastern Pacific storm. The GFS just shows some intense tropical rains over South and Central Florida for several days starting June 2nd.


Drops it? Not what I see.
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142. cchsweatherman
1:29 PM EDT on May 23, 2008
139. KEEPEROFTHEGATE 1:28 PM EDT on May 23, 2008
from sat iam looking at wv levels in w carb should diminish
as dry air fills in behind the movement west looks as theres an area from west carb to just east of trinny with dry air
with itcz adjusted to just south of that also a little dry air cen east atlantic should get pinch and the area fill in itcz also appears to have started a north north west ward movement along ne sa coast it was low over the last little while but appears to be making some gain also there was a void area of convection in that ne area as well and that has rtn as of today


Not meaning to be rude, but I did not understand anything you just said.

Member Since: April 14, 2007 Posts: 8 Comments: 5169
141. beell
5:30 PM GMT on May 23, 2008
Afternoon here to all.

For all you SPC Meso Page users, looks like some new features. 2 and 3 hr changes of various parameters.

For example, added to the "Basic Surface" section,
3hr Temp, Dewpoint, Mix Ratio, and Theta-e change.

There are a few more. Enjoy!

SPC MesoPage
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139. KEEPEROFTHEGATE (Mod)
1:09 PM EDT on May 23, 2008
from sat iam looking at wv levels in w carb should diminish
as dry air fills in behind the movement west looks as theres an area from west carb to just east of trinny with dry air
with itcz adjusted to just south of that also a little dry air cen east atlantic should get pinch and the area fill in itcz also appears to have started a north north west ward movement along ne sa coast it was low over the last little while but appears to be making some gain also there was a void area of convection in that ne area as well and that has rtn as of today
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138. Ivansrvivr
5:22 PM GMT on May 23, 2008
May or June systems are usually flood producers. Flooding is the most dangerous aspect of a tropical system.

The storm over Eastern PBC is a small hail producer.
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136. hurricane23
1:25 PM EDT on May 23, 2008
By the way the NHC has labeled the wave of the african coast with 1010mb low pressure area.

Here is a view of the 12z map...

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135. atmoaggie
5:21 PM GMT on May 23, 2008
neighborhood NE Houston

Humble? Yeah, some of the worst was there (59 cooridor) and I-45.

Mom's new place in Kingwood came out unscathed.

Please don't underestimate the power of a May or early June tropical system

Not me...no way, no how.
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134. Weather456
1:20 PM AST on May 23, 2008
CCH, also this lINK
Member Since: July 24, 2005 Posts: 407 Comments: 19076
133. Ivansrvivr
5:20 PM GMT on May 23, 2008
CC we are getting intense tropical rains now in eastern PBC.

456, you are likely correct about what the season has in store. This will be a classic CV season.
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132. retaining1
5:12 PM GMT on May 23, 2008
106. atmoaggie

Beaumont wasn't too badly hit. There was a lot of flooding, huge amounts of rain... but somewhat predictable. The same roads, intersections and access roads that always flood did again. The same neighborhoods that always flood did again. St. Eliz. hospital figured out why it's unwise to have your emergency room located in a basement 10-feet below ground level in a coastal environment. It is now located on the 2nd floor.

Houston was another story altogether. Neighborhoods and roads that had NEVER flooded got it. In my in-law's neighborhood NE Houston, some houses that had never flooded were up to the 2nd story windows.

Tropical storms can be devestating if they hit the wrong areas at the wrong time, or if they happen to meet a cold front at the wrong place.

Please don't underestimate the power of a May or early June tropical system.
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130. Weather456
1:19 PM AST on May 23, 2008
126. cchsweatherman 1:17 PM AST on May 23, 2008
456, where do you get those satellite images from?


the links are on my blog
Member Since: July 24, 2005 Posts: 407 Comments: 19076
129. hurricane10
12:18 PM EST on May 23, 2008
2008 Hurricane Names

Arthur
Bertha
Cristobal
Dolly
Edouard
Fay
Gustav
Hanna
Ike
Josephine
Kyle
Laura
Marco
Nana
Omar
Paloma
Rene
Sally
Teddy
Vicky
Wilfred
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128. Weather456
1:16 PM AST on May 23, 2008
I must say, the GFS continues to persist with this system, run after run after run.

12Z Run
Member Since: July 24, 2005 Posts: 407 Comments: 19076
127. hurricane10
12:17 PM EST on May 23, 2008
haha tropical wave Arther
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126. cchsweatherman
1:15 PM EDT on May 23, 2008
456, where do you get those satellite images from?
Member Since: April 14, 2007 Posts: 8 Comments: 5169
123. taco2me61
5:07 PM GMT on May 23, 2008
Good Afternoon all:
After seeing the GFS model and just thinking out loud or maybe just typing out loud.... They just might be right about something forming around June 2nd or 3rd..... I will tell you that it would not suprise me at all.... Heck we have not been hit with a storm in 2 years, and I don't think we could go 3 years with out one.....

Just my thinking thats all.....
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122. Weather456
1:14 PM AST on May 23, 2008
119. jphurricane2006 1:12 PM AST on May 23, 2008
456 can you order that thing to keep its pretty spin until I get home? lol


lol...I will try....We'll negotiate to come to some agreement.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
121. atmoaggie
5:08 PM GMT on May 23, 2008
Dang, sorry to hear about the property damage and especially the fatality from the nados.

Couldn't resist this one...ya think Allstate will try and claim that water was responsible for all of the damage for this one? The profit-driven attitude of the legalized thievery companies (read insurance) is despicable. I can hear it now...claims adjuster: "What wind damage?"

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120. TheCaneWhisperer
5:11 PM GMT on May 23, 2008
I said "seems" kinda futile JP, you know I'll be here lol. Just accepting the facts if you will.

Doing well JP, enjoying the smack you in the face heat today. How about you?
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118. Weather456
1:01 PM AST on May 23, 2008
The Tropics

This is a taste of what 08 has in store for us....

Member Since: July 24, 2005 Posts: 407 Comments: 19076
116. weatherblog
5:07 PM GMT on May 23, 2008
Yes, the chances for Caribbean development are now very slim in my opinion. Due to the fact of only marginal favorable conditions in the caribbean, very little model agreement, and because of a tropical storm developing in the Eastern Pacific, I think Arthur may have to wait a while...

July?
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115. TheCaneWhisperer
5:01 PM GMT on May 23, 2008
GFS Beefed up the ghost a bit @ landfall. More rain, yahh. Seems kinda futile to look at it now though, still so far away.
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112. hurricane10
12:07 PM EST on May 23, 2008
can some one give me a link to a good satellite image/loop for the tropical wave
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111. nash28
1:07 PM EDT on May 23, 2008
GFS still develops a Low. 1004mb.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
110. hurricane10
12:05 PM EST on May 23, 2008
LINK! the cmc now developes that EPAC system
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109. cchsweatherman
12:57 PM EDT on May 23, 2008
103. IKE 12:49 PM EDT on May 23, 2008
GFS develops an EAST PAC + a Caribbean system....unusual...


In my opinion, the GFS has dropped the Caribbean system and only shows a strong Eastern Pacific storm. The GFS just shows some intense tropical rains over South and Central Florida for several days starting June 2nd.

Member Since: April 14, 2007 Posts: 8 Comments: 5169
108. weatherblog
5:02 PM GMT on May 23, 2008

Pinhole eye forming?
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107. FLWeatherFreak91
12:59 PM EDT on May 23, 2008
Yes, the newest GFS gives back the chance for this system to hit fl. Rain
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.