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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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.

LOL

Really?

How'd you figure that one out lol.
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56. hurricane23
11:16 AM EDT on May 23, 2008
54. jphurricane2006 11:15 AM EDT on May 23, 2008
Adrian, the QS this morning showed a low, not sure if it was closed though

Really? Have not had a chance to view it.
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55. Patrap
10:16 AM CDT on May 23, 2008
Itsa,Itsa..itsa...May still.

LOL
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53. hurricane23
11:09 AM EDT on May 23, 2008
Thats the key here iam not 100% sure this wave is currently at the surface but from a quick overall view it has an excellent mid-level circulation with it which the NHC makes not of.Looks mostly like everything is in the mid-levels.

Most impressive so far if you asked me.
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51. FLWeatherFreak91
11:11 AM EDT on May 23, 2008
Whooo! t just RAINED (not sprinkled, rained!) But it was only 1/10" and now it's more humid... but It's a start
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50. cchsweatherman
11:02 AM EDT on May 23, 2008
43. TerraNova 10:59 AM EDT on May 23, 2008
it would be funny if it would form, the NHC would be scratching their heads lol

Have they mentioned it in the discussions yet?


...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 26W/27W S OF 12N MOVING W 10-15 KT. WELL
DEFINED MID LEVEL ROTATION IS ALONG THE AXIS NEAR 6N. AREA OF
DENSE CLOUDS WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM
3N-9N BETWEEN WAVE AXIS AND 30W.

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49. TerraNova
11:08 AM EDT on May 23, 2008
8:05 discussion:

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 26W/27W S OF 12N MOVING W 10-15 KT. WELL
DEFINED MID LEVEL ROTATION IS ALONG THE AXIS NEAR 6N. AREA OF
DENSE CLOUDS WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM
3N-9N BETWEEN WAVE AXIS AND 30W.
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46. TerraNova
11:03 AM EDT on May 23, 2008
46 tornadoes were reported to the SPC yesterday. So far only one fatality has been reported, associated with the Colorado tornado. The isolated tornado in California was associated with a freak low precipitation supercell that was invisible to Base reflectivity.

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44. FLWeatherFreak91
10:59 AM EDT on May 23, 2008
27. TampaSpin 10:35 AM EDT on May 23, 2008 Hide this comment.
It appears that a trough in the Gom has alittle spin going and appears to be getting stronger maybe some good rain coming to florida.


Hopefully it gets stronger and is able to pull down a little front to bring some rain to central and south fl
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43. TerraNova
10:58 AM EDT on May 23, 2008
it would be funny if it would form, the NHC would be scratching their heads lol

Have they mentioned it in the discussions yet?
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41. weathermanwannabe
10:55 AM EDT on May 23, 2008
35. jphurricane2006 10:48 AM EDT on May 23, 2008
but see ww, that is the exact thinking I am talking about and this one isnt going poof yet lol


I know JP; we all get pretty excited (and all pro mets and scientists) when an "anomoly" event occurs and blows conventional wisdom out the window....So...You Go That Little Wave Thningie in Late-May!.......
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40. TerraNova
10:54 AM EDT on May 23, 2008
so Terra because its May it cant develop? that is bogus to me

Did I ever say it wouldn't? I was responding to Tampa saying it has little chance. I think you misunderstood my comment...if storms can't develop in May, then Andrea and Barry must have been a dream :p no hard feelings.

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39. AWeatherLover
2:36 PM GMT on May 23, 2008
Its great that the big bend of FL is getting but we need it farther south. Yesterday I recorded 0.13 in of rain and that is it for the past 3 weeks or so.
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38. Squid28
2:52 PM GMT on May 23, 2008
Since we are on the edge of the "official" season, and most everyone has a long weekend coming up I thought this might be a good time to repost an old entry of mine. I figured it mnight be a good time to get people thinking about checking their gear out (generators, chainsaws, extension cords, etc) before a storm is forcast. It can be a real pain in the rear to try and do these activities when a storm is about to drive down your street. Also finding parts for your generato right befoe a storm can be problematic ( trust me, a few year back I was trying to find a correct size battery for my starter with a storm approaching)

Old Post......

Here is a link to one persons input on use and stoarge of a generator and stroing fuel for the same. Although it is a bit mundane for anyone with a lot of experience in the area, for new owners and the un-seasoned it has some good info. I'm a chemist, and spend a lot of time working on oil formulations for various applications relating to hydraulics and internal lubrication of engines. If their is one piece of advice I can give and know what I am talking about, it is too make sure you have adequate oil on hand for keeping the generators topped off. Also, make sure it is the best oil you can get your hands on (if you can source a good synthetic go with it). The last thing you want is for the generator gods to tear away your one source of power at the worst time possible due to thermal breakdown.

Finally, one little extra bit of information on storing fuel in cans.... Regardless of if you use a fuel stabilizer or not (if you don't your crazy), always fill your fuel can up to the neck of the can (works for fuel tanks on equipment too). Yes, it does make it harder to pour the fuel out. The plus to it is, that it reduces the available surface area to be exposed to the air. By reducing the available surface area, you drastically reduce the rate at which the fuel can absorb moisture. As an example (taken from my own five gallon can in the garage) if the can is filled up to the max fill line I have the entire surface area of the interior can space to allow moisture uptake to occur (4.5 x 14=63 sq in). If I fill the can up further towards the neck (4.5x3.5=15.75 ) then I have reduced the surface area to about 16 sq in. Thus reducing my absortion rate by approximateley 75%. This just helps to slow down the effects of moisture and oxygen on the fuel but will not prevent deterioration.

I use Sta-Bil in my tanks, I always add the double quantity for long term storage, and have nothing bad to say about the product. You can buy a jumbo size bottle at Wally World for a good price back in the automotive section. Fuel stabilizers absorb moisture to a point, but that also means that they "attract" moisture, so make sure the cans are sealed up good and tight (don't leave the vent open, otherwise they will suck water in.

Sorry for the novel.....

Link



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36. TerraNova
10:48 AM EDT on May 23, 2008
23 and JP don't think it has a chance either but, it does not need alot more organization to have an invest as healthy as it is looking.

Morning Tampa Spin.

Aren't invests only declared for systems which the NAVY or NHC think have a chance at developing, though? If this won't develop, why would they name it an invest?
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34. hurricane23
10:46 AM EDT on May 23, 2008
You can view some loops of the wave HERE.
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33. TampaSpin
10:43 AM EDT on May 23, 2008
23 and JP don't think it has a chance either but, it does not need alot more organization to have an invest as healthy as it is looking.
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32. epaul
2:40 PM GMT on May 23, 2008
You all may already know of this site but I just discovered it yesterday. Live cams when the storm chasers are out and about. I watched one kansas tornado live yesterday. They had chasers all the way from NW Oklahoma to Nebraska:

http://www.severestudios.com/livechase
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31. weathermanwannabe
10:23 AM EDT on May 23, 2008
19. tillou 10:22 AM EDT on May 23, 2008 Lol....A little something to watch....I've have metioned this before, but, in one of the NOAA publications from Year 2000 (Mariners' Guide to Tropical Cyclones), the climatology suggests (as to the Cape Verde season)that about 60 discernable tropical waves emerge off the coast of Africa during H-Season and "cross" the tropical atlantic...Of course, out of those numbers, a very small percentage survive the crossing intact (approaching the Lesser Antilles), and, form into tropical depressions.......Point is that while fun to look at, it is way too early to expect any sustained tropical development from these "early waves", and, once the real train gets started in August, we will all see the majority of the emerging waves "go poof" for various reasons. Of course, the "chosen few" will get through and go on to potentially threaten the Caribbean and US; seems like many on here are expecting a busy Cape Verde season and I'm sure that it will be the case, but, a busy season (60 plus waves) does not translate into 60 storms...............
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29. hurricane23
10:38 AM EDT on May 23, 2008
I must say iam very impressed with the overall structure of this wave in the eastern atlantic.One of the most impressive so far this season.

Here is a nice view.

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28. Squid28
2:36 PM GMT on May 23, 2008
Thanks for the help, I was able to find it with everyones guidance.
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27. TampaSpin
10:34 AM EDT on May 23, 2008
It appears that a trough in the Gom has alittle spin going and appears to be getting stronger maybe some good rain coming to florida.
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26. IKE
9:30 AM CDT on May 23, 2008
Squid28...it has to be approved...mine took several hours.
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25. smmcdavid
9:29 AM CDT on May 23, 2008
Hey squid... when you go to my photos, there is a box you have to check for your primary portrait. that should fix the prob.
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24. IKE
9:28 AM CDT on May 23, 2008
LOL....

The ECMWF has been consistent with east PAC development...eventually making landfall as it turns north.
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23. Squid28
2:26 PM GMT on May 23, 2008
Okay, I have a question, and it is probably one of those "slap me in the face" type of deals once someone helps me with this. I have one photo uploaded on WU to use as my picture. Can someone tell me how to get it to appear, or put up a link to an FAQ etc, as everywhere I have looked I'm turning up zilch...

Thanks
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22. hurricane23
10:28 AM EDT on May 23, 2008
Good morning!

Indeed the GFS has had poor model support from other models infact its been a longe-range prediction which have of the time does not pan out due to the models poor skill level that far out.Either way as overall upper level conditions become more favorable in the next few days something might try to pop in the pacific.
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20. pearlandaggie
2:24 PM GMT on May 23, 2008
ECMWF....sounds like a wrestling show! :)
Member Since: September 14, 2007 Posts: 3 Comments: 3963
19. tillou
2:22 PM GMT on May 23, 2008
Since everyone seems to have their eyes glued to the EP and SWCarr, take a look at the east atl. 7 degrees north and 30 degrees east. Got a nice little spin to it.

Link

I don't think it will make to far, but heah its "blob" watching at it finest. LOL!
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18. groundswell
2:16 PM GMT on May 23, 2008
HOWEVER...THIS ALSO WILL ALLOW A LONG NORTH TO NORTHEAST
FETCH TO DEVELOP OVER THE WEST ATLANTIC...WHICH WILL PUSH NORTHEAST
SWELL INTO THE LOCAL WATERS THROUGH EARLY NEXT WEEK.

Looks like there is always surf on major holiday weekends...get ready for a workout as looks like power chop is on tap.

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17. IKE
9:15 AM CDT on May 23, 2008
cchs...agree...the GFS is about the only model showing western Caribbean development...I'm just saying it's been consistent with that. Maybe it's wrong...time will tell.
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16. IKE
9:13 AM CDT on May 23, 2008
The 0Z GFS...takes the pre-blob/ghost north eventually into the big-bend of Florida.

The 6Z GFS takes it further west into the western GOM.

See if the 12Z GFS trends further south and west.
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15. cchsweatherman
10:06 AM EDT on May 23, 2008
Good Friday morning all! My visit to the NHC got cancelled this morning as the meteorologist I was supposed to meet with could not be available.

Well, IKE, I have to agree with Dr. Masters somewhat. The GFS is really the only model showing a developing storm in the Caribbean, while all other models show a developing Eastern Pacific storm. In addition, the track and strength has changed quite often with the "ghost" storm in the model. But, Dr. Masters should not be so quick in discounting the model as it has been persistent on development in the West Caribbean and conditions would seem favorable for tropical cyclogenesis there. Dr. Masters should remember that there was only one model (the CMC) that predicted Hurricane Humberto forming last year when there were no other models even showing any signs, so it could still be possible that the GFS could be correct. Either way, time will only tell.
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14. AWeatherLover
2:07 PM GMT on May 23, 2008
I guess Dr. M doesn't think we will be getting the much needed rain here in FL like the GFS was saying. Can anyone post a pic of the 00z run of the model? I'm not by a computer today. (reading the blog from my phone) Thanks!
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12. IKE
8:58 AM CDT on May 23, 2008
Dr. Masters said......."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.".......


Inconsistent???? The GFS???? It's been on every model run the last few days.
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10. Squid28
1:57 PM GMT on May 23, 2008
Morning everyone, anything cooking anywhere (tropically speaking, it has ben a few days since I checked out any of the models or even read an outlook.
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8. lickitysplit
1:37 PM GMT on May 23, 2008
My uncle's house in Windsor was severly damaged. He was visiting a friend down the street and has no injuries whatsoever.
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7. smmcdavid
8:35 AM CDT on May 23, 2008
Thanks for the update Dr. M!

The tornado video is just amazing... so much power. I couldn't take my eyes off of it. Hopefully the weather will be a little "nicer" today.
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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.