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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1107. StormJunkie
5:45 PM GMT on May 24, 2008
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1106. TerraNova
1:44 PM EDT on May 24, 2008
As of now iam leaning towards some development in the pacific which is were thunderstorm activity apparently is trying to organize.The GFS may have the right idea but wrong basin wise.

I think the ECWMF and GFS are depending on the monsoon trough to lift northward due to the upward MJO pulse, which is possible.
Member Since: July 30, 2007 Posts: 76 Comments: 4063
1105. Ivansrvivr
5:42 PM GMT on May 24, 2008
1094. It looks like the whole peninsula will pop at same time on radar. The only thing not in your favor is the westerly steering pattern. That should change by tomorrow.
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1104. StormJunkie
5:43 PM GMT on May 24, 2008
23, I don't think genesis is expected to happen in the next couple of days. That said, that general area is supposed to shift back to the E and N correct?
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1103. weathersp
1:43 PM EDT on May 24, 2008
Hi all! Any new devlopments from the EPAC storm from early this morning?
Member Since: January 14, 2007 Posts: 17 Comments: 4140
1102. hurricane23
1:43 PM EDT on May 24, 2008
As of now iam leaning towards some development in the pacific which is were thunderstorm activity apparently is trying to organize.The GFS may have the right idea but WRONG basin wise.

HERE is a view of the area.
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1100. hurricane23
1:41 PM EDT on May 24, 2008
.
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1099. nash28
5:41 PM GMT on May 24, 2008
LOL Ivan!
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1098. Ivansrvivr
5:39 PM GMT on May 24, 2008
Nash it wasn't me, It was the cat. I am too lazy to post so I make the cat do it. I was just too lazy to proof read Mo's typing.
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1097. Ivansrvivr
5:36 PM GMT on May 24, 2008
The sun is out here in WPB, but there are very dark clouds to the north. Those "light showers" wont stay light for long. That is probably east coast seabreeze about to pop.
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1094. nash28
5:36 PM GMT on May 24, 2008
Hey StormW! Looks like the seabreeze and boundary collision further EWD screws our rain chance today...

Ah well.
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1093. nash28
5:36 PM GMT on May 24, 2008
I know Ivan. I figured you mixed up the names:-)
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1091. hurricane23
1:34 PM EDT on May 24, 2008
Few light showers have developed here across extreme se florida which could actually help out the situation with cloud cover keeping things under severe limits later this afternoon.
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1090. Ivansrvivr
5:33 PM GMT on May 24, 2008
Nash you are right, I meant Drakoen. I apologize for the mixup. That is what happens when you let a cat to your posts out of laziness.
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1089. Drakoen
5:34 PM GMT on May 24, 2008
1085. nash28 5:31 PM GMT on May 24, 2008
Ivan- I didn't make a TCHP comment:-)


It was me lol.
Member Since: October 28, 2006 Posts: 57 Comments: 30494
1087. Ivansrvivr
5:30 PM GMT on May 24, 2008
KOTG, I know Columbus had a run in with a hurricane on one of his cruises. He lost one or two of his ships in the storm.
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1086. BahaHurican
1:31 PM EDT on May 24, 2008
BBL, guys, cause I gotta make a run.

Member Since: October 25, 2005 Posts: 19 Comments: 22143
1085. nash28
5:31 PM GMT on May 24, 2008
Ivan- I didn't make a TCHP comment:-)
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1084. BahaHurican
1:27 PM EDT on May 24, 2008
1079.

Interesting pic, Pat. I think I understand now why the Chandeleurs are not growing. If all that sediment used to wash out via the Mississippi's "back door", it was prolly building those islands, at least partially.
Member Since: October 25, 2005 Posts: 19 Comments: 22143
1083. KEEPEROFTHEGATE (Mod)
1:20 PM EDT on May 24, 2008
theres a jornal dated 1495 with the same quote dated 1495 aug 29 and also sept 1498 then 1508 7 yrs later 12 august storm struck dominca republic destroy entire village and population of buena ventura hes date for america was 1497 i think maybe some one else would know
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1082. Ivansrvivr
5:25 PM GMT on May 24, 2008
Nash, I was only pointing out that anything developing in Caribbean would probably not become cat 3 or 4 and wipe out the Gulf Coast. I wasn't ruling out tropical development at all. (If your TCHP reference is to me).
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1081. StormJunkie
5:26 PM GMT on May 24, 2008
Nice image pat. Sediment really stands out!
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1079. Patrap
12:25 PM CDT on May 24, 2008
SJ, a sweet MODIS image of the River delta here and the cold water sediments from the High River spilling into the GOM. Looking closely you can see the Lake Muddied from the Spillway opening and the 25 mile long Causeway Bridge.Link
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1078. TerraNova
1:24 PM EDT on May 24, 2008
12z CMC develops the EPAC low but not the Caribbean low.
12z UKMET develops the EPAC low and also shows a weak, broad low pressure system near the Yucatan. Maybe a sign that the UK model is starting to catch on?
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1077. StormJunkie
5:22 PM GMT on May 24, 2008
Would need to see much more then one reading, but WSW to NNW wind shift is interesting.
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1076. nash28
5:23 PM GMT on May 24, 2008
The Low off the coast of FL is the responsible party for the severe weather in FL today.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1075. Drakoen
5:21 PM GMT on May 24, 2008
I think some here are confusing the TCHP with whether or not a system will be able to develop. Generally 26C shallow waters can support a weak shallow tropical cyclone. The TCHP takes into account the ocean depth at 150 meters with the 26C isotherm. A TCHP value of 80 or higher is highly favorable for intensification of a storm and can support a hurricane. TCHP involves how fast a system will be able to intenisfy with the given temperatures in the ocean depth.
Member Since: October 28, 2006 Posts: 57 Comments: 30494
1074. MasterForecaster
5:21 PM GMT on May 24, 2008
Hey guys I see you were refering to the 1478 season...I found a few interesting blog posts.

851. ChrisColumbus 1:41 PM GMT on May 24, 1478
Does anyone know if this wave is going to become a hurricane? I'm planning a trip to the other side of the world.


851. SantaMariaCaneWatcher 1:43 PM GMT on May 24, 1478
Columbus how many times do I have to tell you the model's aren't advanced enough yet we have to wait a few thousand years. As for the wave all we can do is watch and wait.


851. PintaShipCaneCaptain 1:46 PM GMT on May 24, 1478
Is anyone else having a problem posting comments?
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1073. nash28
5:21 PM GMT on May 24, 2008
Just saw the 12z GFS. Interesting... I pray this verifies, because it would bring copious amounts of moisture to the W. Central FL area for a couple of days.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
1072. Weather456
1:20 PM AST on May 24, 2008
1069. Ivansrvivr 1:20 PM AST on May 24, 2008

oh i c
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1071. Patrap
12:22 PM CDT on May 24, 2008
vary intersting we were saying in StormChat
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1070. StormJunkie
5:20 PM GMT on May 24, 2008
lol pat, I been trying to mention it for days on end!

Not likely to be much of anything, but it is kind of a cute little sucker :~)
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1069. Ivansrvivr
5:18 PM GMT on May 24, 2008
456. No need to go back and look, this is more like late season pattern anyways.
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1068. Patrap
12:19 PM CDT on May 24, 2008
I was wondering if anyone was going to see or mention that er,thing SJ.

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1067. KEEPEROFTHEGATE (Mod)
1:18 PM EDT on May 24, 2008
i see sj
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1066. Patrap
12:14 PM CDT on May 24, 2008
Hurricanes thru History with interactive Maps too. A Keepa Link here. Link
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1065. Ivansrvivr
5:13 PM GMT on May 24, 2008
KOTG that was after Columbus had discovered Hurricanes along with America correct?

Westerlies look widespread over E-Pac. there is cyclonic turning over Yucatan. Probably same turning that 456 saw yesterday in SW Caribbean. The question is how does this low respond to front passing thru Florida?
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1064. Weather456
1:13 PM AST on May 24, 2008
1061. Ivansrvivr 1:13 PM AST on May 24, 2008
1047, both those examples are late season storms. Usually when development is likely in that area, in the early season the E-Pac wins out, late season the W.Caribbean wins out. Usually winds are east/southeast in the E-Pac and W.Caribbean in June. By October the easterly trades die out, E-Pac development gets drawn north into Mexico and W.Caribbean development usually moves north towards GOM.
TCHP is marginal over the W.Caribbean, so whatever develops wont get very strong.


Yeah I know....just use a few general examples...It had some examples for early season but I wud have to go and look.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1063. StormJunkie
5:16 PM GMT on May 24, 2008
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1062. Drakoen
5:14 PM GMT on May 24, 2008
1061. Ivansrvivr 5:13 PM GMT on May 24, 2008
1047, both those examples are late season storms. Usually when development is likely in that area, in the early season the E-Pac wins out, late season the W.Caribbean wins out. Usually winds are east/southeast in the E-Pac and W.Caribbean in June. By October the easterly trades die out, E-Pac development gets drawn north into Mexico and W.Caribbean development usually moves north towards GOM.
TCHP is marginal over the W.Caribbean, so whatever develops wont get very strong.


The TCHP is even worse in the EPAC lol.
Member Since: October 28, 2006 Posts: 57 Comments: 30494
1061. Ivansrvivr
5:06 PM GMT on May 24, 2008
1047, both those examples are late season storms. Usually when development is likely in that area, in the early season the E-Pac wins out, late season the W.Caribbean wins out. Usually winds are east/southeast in the E-Pac and W.Caribbean in June. By October the easterly trades die out, E-Pac development gets drawn north into Mexico and W.Caribbean development usually moves north towards GOM.
TCHP is marginal over the W.Caribbean, so whatever develops wont get very strong.
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1060. KEEPEROFTHEGATE (Mod)
1:03 PM EDT on May 24, 2008
year 1498 west indies

Christopher Colombus stated 600 yrs ago

"nothing but the service of god or the extension of monarchy would expose me to such danger".
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1058. Drakoen
5:07 PM GMT on May 24, 2008
Those westerlies in the EPAC could slip over into the Caribbean with the advancement of the monsoon trough. The orography and shape of the landscape easily induces a closed area of low pressure north of Panama.
Member Since: October 28, 2006 Posts: 57 Comments: 30494
1057. Weather456
12:57 PM AST on May 24, 2008
Notice how the southwesterlies south of the system freshens....thats an indicator of a northward push in the monsoon trough probably induced by the MJO.



Total Cloud Cover

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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.