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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2107. StormJunkie
12:11 AM GMT on May 26, 2008
Ditto nash, can not wait until we get to put a foot down over there. Can only hope I get to live long enough to see it.
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2106. surfmom
12:05 AM GMT on May 26, 2008
hopefully this is the start of a future job for my young buck - his eyes are sparkling with excitement watching the control crew etc. (thanks for the great links patrap) This is what gives our kids hope, direction and purpose - what a terrific "UP" for all of us. It's all been rather dismal news lately --this is just GREAT! Watching my kid view this, I see he recognizes his dreams can be a reality! It makes all his geometry, algebra, science, chem, etc. have a purpose!
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2105. aspectre
12:07 AM GMT on May 26, 2008
First pictures from the Phoenix due in about an hour and a half.
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2104. nash28
12:10 AM GMT on May 26, 2008
Just fantastic! I myself am speechless.
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2103. StormJunkie
12:09 AM GMT on May 26, 2008
Sure you are listening mlc, but just in case, 90 minutes until first pictures :~)
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2102. Drakoen
12:09 AM GMT on May 26, 2008
I'll be here for the first picture and the 00z GFS run LOL...
Member Since: October 28, 2006 Posts: 57 Comments: 30561
2101. StormJunkie
12:08 AM GMT on May 26, 2008
lol mlc!
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2100. nash28
12:08 AM GMT on May 26, 2008
Right on the button folks! Unbelievable!!!! I am so PROUD of that team!!!!! PROUD!
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2099. moonlightcowboy
7:06 PM CDT on May 25, 2008
2090. aspectre 7:02 PM CDT on May 25, 2008
....Welcome to the North Pole of Mars."



....be a heckuva note to find lil green men in parkas! ; P
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2098. weathersp
8:03 PM EDT on May 25, 2008
Phoenix lander landed 1/4 of a degree tilt. That's Amazing.
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2097. surfmom
12:04 AM GMT on May 26, 2008
Stormjunkie - LOL
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2096. surfmom
12:02 AM GMT on May 26, 2008
This is amazing - so far away ...yet so close!
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2094. StormJunkie
12:02 AM GMT on May 26, 2008
wsp, that was the plan all along :~) Free fall to 5mph in a couple hundred feet.
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2093. moonlightcowboy
6:56 PM CDT on May 25, 2008
2078. Gotcha 456, but weeks ago we came to consensus in here that most dust rides at the mid-levels. The cATL shows really nothing in the upper levels and only a spot in the mids. Water vapor looks plentiful and Navy's TPW product pretty much reflects that, too.

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2092. nash28
12:02 AM GMT on May 26, 2008
Historic day. For our country!
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2091. weathersp
8:00 PM EDT on May 25, 2008
COM guy had me going there when he said that it was in confirmed free fall and he was counting of the Altitude in Hundreds of meters per couple of seconds. Until he said 30 meters then 4 seconds later 27 meters.. and it kept slowing down..
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2089. StormJunkie
12:00 AM GMT on May 26, 2008
Those are the guys and gals I want in office. Folks say it is too hard to get away from oil, BS!

Nice job Nasa, JPL, and Lockheed!!!
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2088. cchsweatherman
8:00 PM EDT on May 25, 2008
CONGRATS NASA!!! What a historic day.
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2086. nash28
11:56 PM GMT on May 25, 2008
What a feeling!!! Awesome!
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2085. cchsweatherman
7:56 PM EDT on May 25, 2008
Just emailed John Gerard at NBC6 in South Florida to get his professional opinion on the possible situation. I will let you all know what he has to say.
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2084. Patrap
6:57 PM CDT on May 25, 2008
The Phoenix has landed.



Member Since: July 3, 2005 Posts: 426 Comments: 128630
2083. Patrap
6:57 PM CDT on May 25, 2008
confirmation..Carrier wave lock-up..
Altitude is on the surface.
Readback on the recorders for data .


Looks like were on the surface 5 X 5.

Out-freaking standing..What a ride.
Member Since: July 3, 2005 Posts: 426 Comments: 128630
2082. extreme236
11:54 PM GMT on May 25, 2008
From the EPAC TWD:

TROPICAL WAVE PREVIOUSLY ANALYZED OVER LAND 90W APPEARS ONLY IN
DATA OVER THE GULF OF MEXICO AND THEREFORE WILL BE DROPPED FROM
THE ANALYSIS IN THE E PAC. A BROAD AREA OF SW TO W WINDS
CONTINUE OVER THE WATERS FROM 05N TO 11N BETWEEN 90W AND 102W.
GLOBAL MODELS ARE FORECASTING A BROAD AREA OF LOW PRESSURE TO
DEVELOP NEAR 10N90W OVER THE NEXT SEVERAL DAYS.
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2081. FLWeatherFreak91
7:54 PM EDT on May 25, 2008
Congrats NASA and USA for successful Martian entry!

On a less-exciting note, the 18z nogaps has slowed the system significantly after development, strengthens it, and moves it further east.
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2080. stormhank
11:55 PM GMT on May 25, 2008
mail drak
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2079. StormJunkie
11:53 PM GMT on May 25, 2008
Bad Ass!

scuse the french
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2078. Weather456
7:50 PM AST on May 25, 2008
2053. moonlightcowboy 7:43 PM AST on May 25, 2008

When evaluating conditions out there, it is best to evaluate all layers, like the surface humidity which can be assess using the TPW product.
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2077. weathersp
7:53 PM EDT on May 25, 2008
IT MADE IT!!! WOOOO!!!!

TOUCHDOWN!!
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2076. weathersp
7:52 PM EDT on May 25, 2008
Landing Gear deployed..
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2075. nash28
11:52 PM GMT on May 25, 2008
My bad then Drak. FSU is the page I usually use., My apologies.
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2074. weathersp
7:51 PM EDT on May 25, 2008
Parachute Successfully deployed.. Heatshield jettisoned.
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2073. Drakoen
11:50 PM GMT on May 25, 2008
2066. nash28 11:50 PM GMT on May 25, 2008
They must have changed then Drak, because they only ran twice per day. The UKMET runs 4 times.


Its just that FSU doesn't process the run.
Member Since: October 28, 2006 Posts: 57 Comments: 30561
2072. nash28
11:50 PM GMT on May 25, 2008
CONGRATS NASA!!!!!!
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2071. Patrap
6:51 PM CDT on May 25, 2008
If you have cable try CH 101
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2070. weathersp
7:50 PM EDT on May 25, 2008
Wating for Parachute Deployment conformation.
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2069. Patrap
6:49 PM CDT on May 25, 2008
If landing is successful..Data first light will be like in 2 Hours Post landing.
Member Since: July 3, 2005 Posts: 426 Comments: 128630
2068. nash28
11:50 PM GMT on May 25, 2008
I am watching the stream on Phoenix. Amazing.
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2067. Drakoen
11:49 PM GMT on May 25, 2008
2065. StormJunkie 11:49 PM GMT on May 25, 2008
Think those JPL/Nasa/Lockheed folks are sitting on pins and needles right now?


They should be. Everything is so technical.
Member Since: October 28, 2006 Posts: 57 Comments: 30561
2066. nash28
11:48 PM GMT on May 25, 2008
They must have changed then Drak, because they only ran twice per day. The UKMET runs 4 times.
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2065. StormJunkie
11:47 PM GMT on May 25, 2008
Think those JPL/Nasa/Lockheed folks are sitting on pins and needles right now?
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2064. weathersp
7:47 PM EDT on May 25, 2008
Temperature of Heatshield of the vehicle is near 2400 degrees fahrenheit.
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2063. moonlightcowboy
6:48 PM CDT on May 25, 2008
Pat, how long do you think it'll be (have they said) before we'll see any pictures?
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2062. surfmom
11:45 PM GMT on May 25, 2008
RE:2032 - that's what makes some of the best waves gomex surfers get. Dean extraordinary, Wilma - world class heavy water
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2061. Drakoen
11:47 PM GMT on May 25, 2008
2057. nash28 11:45 PM GMT on May 25, 2008
NOGAPS doesn't run an 18z, to my knowledge. I thought only every 12hrs at 00z and 12z.


It does. It runs like the GFS 00z, 06z, 12z, 18z
Member Since: October 28, 2006 Posts: 57 Comments: 30561
2060. Patrap
6:47 PM CDT on May 25, 2008
Member Since: July 3, 2005 Posts: 426 Comments: 128630
2059. StormJunkie
11:46 PM GMT on May 25, 2008
That is what I thought as well a nash, but it seems that FNOMC runs it, just FSU does not process the 6 & 18z.

Entry has begun!!!

Go Phoenix!
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2058. weathersp
7:42 PM EDT on May 25, 2008
1 Minute till Martian Atmosphere Entry...
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2057. nash28
11:43 PM GMT on May 25, 2008
NOGAPS doesn't run an 18z, to my knowledge. I thought only every 12hrs at 00z and 12z.
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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.