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

By: Dr. Jeff Masters , 1:23 PM GMT on May 23, 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
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

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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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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106. atmoaggie
4:58 PM GMT on May 23, 2008
I was in Houston and Beaumont for Allison

Hah...me too. (Both of them)
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105. groundswell
4:56 PM GMT on May 23, 2008
that wave in the central atlantic looks like it's headed into a high shear area in 48 hours.Nice structure now though...
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104. keywestdingding
4:48 PM GMT on May 23, 2008
sure wish they would fix the GOM's sst's on here. its a great map.
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103. IKE
11:48 AM CDT on May 23, 2008
GFS develops an EAST PAC + a Caribbean system....unusual...
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102. TexasGulf
4:26 PM GMT on May 23, 2008
Really bad storms CAN form in May. We wouldn't expect a major hurricane to form early. Depending on conditions, tropical storms can be equally damaging.

Look at Tropical Storm Allison, made landfall June 5, 2001 in Houston. That storm dumped anywhere from 20-30+ inches of rain in the Houston area. It circled around to the gulf, re-hit the same region again.

Allison is on the all time list of greatest damage, but it was only a tropical storm. I was in Houston and Beaumont for Allison. I remember all the cars stalled on the highway, flooded homes that normally would never flood... it was bad.

May is perfectly capable of producing damaging tropical storms. It really depends on circumstances.
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101. IKE
11:44 AM CDT on May 23, 2008
12Z GFS....through 384 hours...Link
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100. JRRP
4:34 PM GMT on Mayo 23, 2008

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99. smmcdavid
11:42 AM CDT on May 23, 2008
Does anyone know where I can find comparison pictures of different category hurricane damage?

I know/have the damage descriptions, but would love to have pics. Thanks!
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97. TerraNova
12:33 PM EDT on May 23, 2008

A new puff of convection has appeared north of the center, but most of the convection to the center's south has waned.
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96. DocNDswamp
11:15 AM CDT on May 23, 2008
LOL you betcha Pat... had plenty up close experiences with both Allison and Cindy... as made trip to E TX during early going with Allison, driving thru hvy rains, then got above worst of it in the Piney Woods while Houston was getting blasted... Then couple days later crossed paths with the redeveloping TS on way back, into more hvy rains as got home in SE LA... center passed right over...

Cindy was a trip in it's own right... I remember thinking "here we go, another weak fizzler"... after all a lot of shear was impacting it, then watched with astonishment as it intensified to hurricane force making landfall... LOL, had a few anxious moments late that night as it did a temporary stall and took a brief NW jog (beyond the frame of that loop), giving us quite a blast of blinding rain and winds, causing me to change my sceptical view of Cindy - "Please don't let my neighbor's oak tree fall on my house"... LOL... Viewing that loop, notice around 6 PM when that intense band developed and hit lower Lafourche - a supply boat / tug anchored at Fourchon reported a 105 mph gust from it...
BTW, per our discussion last night - that Cindy radar loop played just fine in my browser today...
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93. Patrap
11:26 AM CDT on May 23, 2008
Cindy 2005 stats from the wu-archive on the Tropical Page Link
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92. nrtiwlnvragn
12:24 PM EDT on May 23, 2008
82. TerraNova

This presentation, Baseline Instruments for the GOES-R Series: Providing Major Improvements to Hurricane Observations gives an overview of the GOES series and the future planned improvements.

CAUTION: Large Powerpoint file that has to be downloaded ~40MB
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12:01 PM EDT on May 23, 2008
cane addick are you at it again
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90. TerraNova
12:18 PM EDT on May 23, 2008
GFS is still at it...at the time however I think I'm going to trust model consensus more than consistency. The other models should be coming out momentarily. According to the new run, the disturbance responsible for this possible cyclone will make it's debut on Monday or Tuesday.

The new GFS does not develop a low with the East Atlantic wave.

GFS out 114 hours:
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88. PetesGirl
9:15 AM PDT on May 23, 2008
Hail in Southern California. What's up with that?
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87. jake436
4:14 PM GMT on May 23, 2008
Patrap, long time no type for me. What was the date of Hurricane Cindy's formation? I know it was fairly early...June something.
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86. hahaguy
12:15 PM EDT on May 23, 2008
hopefully we get some in st lucie
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85. Ivansrvivr
4:11 PM GMT on May 23, 2008
Looks like it will rain again today in Palm Bch Co. Cumulus are towering and darkening and it is just noon.
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84. Patrap
11:13 AM CDT on May 23, 2008
Cindy July 2005, Cat-1 Local Landfall Loop Link

7 weeks Later..Link
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11:42 AM EDT on May 23, 2008
64. Patrap 11:29 AM EDT
Im a realist..not a Florida westcaster Dude.

I resemble that remark.
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82. TerraNova
12:08 PM EDT on May 23, 2008
GOES-O (GOES-14) is scheduled for August launch.

Thanks...I wasn't aware they were expanding on the GOES program. Wonder what GOES O and P are for...
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81. Patrap
11:05 AM CDT on May 23, 2008
June 6-19 2001 Link
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80. Bamatracker
4:06 PM GMT on May 23, 2008
hey jp....how was your winter man? where is that wave you all were looking at?
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79. nrtiwlnvragn
12:00 PM EDT on May 23, 2008
76. atmoaggie

GOES-O (GOES-14) is scheduled for August launch.

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78. Patrap
10:56 AM CDT on May 23, 2008
Seen Many a May System go Boom, and first week of June too.
All one has to do is go back to the first week in June 2001.

One wont find the Supers in May and June usually. But it dont have to be A cranked up tight Cat 3 to do the nasty in Billions of Dollars.

And even in July,,the GOM can spring a Wam on yer like in 60 hours.
Like that first cane to hit Se La. in 2005.

Most wont ever mentioned that Wallop,nor remember that it even traveled way inland to Georgia and Spun off Nadoes that ripped the roof the Atlanta Motor Speedway.

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76. atmoaggie
3:56 PM GMT on May 23, 2008
Not really tropical-related, but interesting...(This instrument measures stratospheric ozone)

"On 22 May 2008, JDay 143 at approximately 11:55a.m (eastern time) a
NOAA-18 SBUV Motor Current began to rise anomalously. At that time the
spacecraft was out of contact with the ground and in the South Atlantic
Anomaly at approximately 32 degrees South and 28 degrees West. The
motor temperature quickly began to follow the current. By the time of
the next spacecraft contact the motor current and temperature were out
of limits. We have not seen abnormal behavior in other parts of the
instrument, except a slight increase in the grating drive temperature
which may be due to heat leaked from the motor.
SOCC engineers are investigating. This appears to be a serious anomaly
based on the telemetry we are seeing at SOCC. The motor impacted is
needed for proper calibration of SBUV. Products using NOAA-18 SBUV data
may be impacted."

Shows you how things just might go wrong, even on our younger satellites. These events are why the Europeans have launched redundant satellites in the Meteosat series and simply parked the extra one until it is needed. Smart...
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75. CaneAddict
3:57 PM GMT on May 23, 2008
JP, I don't want trouble either, It's NOT about you discussing development of anything actually, It is about how you seem to think your opinion is more over the other bloggers, I may be wrong and may just be over reacting to the situation but that's my opinion, On the other hand you make great post's....just sometimes though you seem to get a little over ruling. JMO though, I still respect you for what you do as far as contribution to the blogs.
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73. DocNDswamp
10:52 AM CDT on May 23, 2008
Greetings all,

Hmmmmmm, yep it's May alright... but check that calendar closely - we're one week away from June!

Which makes me somewhat puzzled why Dr Jeff mentions May storms in W Carib / Gulf being a climatological oddity - the GFS has been showing the time frame for potential development there consistently between May 30 and June's first couple days... Certainly within the realm of reason and no way would I discount the GFS runs for - at the least - a tropical depression in W Carib / Gulf... On several runs the GFS also shows a TC forming close to same period in the E Pac... which would not be a surprise considering many runs of the GFS show that sprawling area of low pressure resembling a monsoon trough which could easily spawn more than one low pressure entity... We should be seeing some signs by mid next week of early stages of development and certainly when under 192 hrs somewhat better resolution of the features...

And LOL, someone tell me how well those other models did past couple seasons verses the GFS overall...
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70. TerraNova
11:45 AM EDT on May 23, 2008
the wave in EATL has chance to develop?

It has a chance but it's very slim. Although it's currently in a pretty supportive environment, as it moves further west, it will encounter dry air and higher wind shear. In any case it's the only thing to watch out for the time being.
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69. JRRP
3:37 PM GMT on Mayo 23, 2008
the wave in EATL has chance to develop?
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68. TerraNova
11:40 AM EDT on May 23, 2008
Amazing stuff!

Look at 0:04...geez, I wonder what the people in those cars were thinking at that moment...very scary. From what I've heard only one fatality has been reported thus far.
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66. TerraNova
11:38 AM EDT on May 23, 2008
12z GFS is now running
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65. Patrap
10:29 AM CDT on May 23, 2008
The QuikSCAT DATA is available on every NDBC Buoy Page...

But We wont look at the QuikSCAT till we need too.

And today aint it...,,

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63. hurricane23
11:28 AM EDT on May 23, 2008
Scary sight...

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61. hurricane23
11:17 AM EDT on May 23, 2008
Chances are that nothing to significant will come about from this wave as its still way early but those rather impressive waves just keep coming.If this were august LOOK OUT.
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60. weathermanwannabe
11:17 AM EDT on May 23, 2008
41. weathermanwannabe 10:58 AM EDT on May 23, 2008....So...You Go That Little Wave Thningie in Late-May!.......

You Go Poof...........

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57. hurricane23
11:16 AM EDT on May 23, 2008
55. Patrap 11:16 AM EDT on May 23, 2008
Itsa,Itsa..itsa...May still.



How'd you figure that one out lol.
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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