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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.

Reader Comments

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1607. nash28
3:55 PM GMT on May 25, 2008
I see the ridge is forecast to be somewhat of a blocking mechanism.
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1606. Drakoen
3:55 PM GMT on May 25, 2008
1603. nash28 3:54 PM GMT on May 25, 2008
Vort got banned???

I must have missed something last night.

Yea. Its probably because he disrespected me in the blog yesterday.
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1605. Drakoen
3:51 PM GMT on May 25, 2008
1601. nash28 3:50 PM GMT on May 25, 2008
I see there is still somewhat of a split as to which basin this Low will be in.

Sort of. Initially the models are saying a low will form in the Caribbean. The consensus is that the low will cross over and strengthen in the Caribbean. The models are imposing this lower to mid level ridge over the GOM which may allow the system to going into the BOC. There will be a low pressure system over the northern Central Plains region but the models think the Jet stream will be far enough north for it to not have much of an effect on the ridge.
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1604. Michfan
10:54 AM CDT on May 25, 2008
Good morning everyone. Whats the word today on the models?
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1603. nash28
3:54 PM GMT on May 25, 2008
Vort got banned???

I must have missed something last night.
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1602. Stormchaser2007
11:51 AM EDT on May 25, 2008
I think Vort got banned IMO........
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1601. nash28
3:50 PM GMT on May 25, 2008
I see there is still somewhat of a split as to which basin this Low will be in.
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1600. nash28
3:47 PM GMT on May 25, 2008
Morning all. What happened to Vort's blog?
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1599. Drakoen
3:43 PM GMT on May 25, 2008
Another thing to consider is how much cyclogenesis will occur with the system in the EPAC before it crosses over into the Caribbean.
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1598. TexasGulf
3:38 PM GMT on May 25, 2008
Y'all in the midwest have been sucking in our warm Gulf air for the past week.

The steady wind and warm air flowing North out of Texas has been wreaking havoc. My tomato plants are drying up, swimming pool needed to be topped off and my wife had three 'bad hair days' this week.

Enough with the wind. The Midwest has been enjoying your violent weather, but its time to calm down now and keep the southern Gulf breeze in the south. Warm air doesn't grow on trees, you know. Stop sucking it all away from Texas.
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1597. Stormchaser2007
11:41 AM EDT on May 25, 2008
Heres the cross over storm. (NOGAPS)

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1596. weatherfromFlorida
3:40 PM GMT on May 25, 2008
Aww, Nasaspaceflight's blogs down, how am I gonna watch the Mars Landing?
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1595. weathersp
10:53 AM EDT on May 25, 2008
Hi all!

Whats the news of the day?
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1594. ShenValleyFlyFish
3:40 PM GMT on May 25, 2008
Peeved at Prices? Don't Blame the Dealer
Awash in Profit, Exxon Fights for Pennies While Raising the Rent

Exxon keeps Sohaila Rezazadeh's profit to pennies on the gallon, even as it raises the lease on her Oakton station by about 10 percent a year. (By Lois Raimondo

Every time Sohaila Rezazadeh rings up a sale at her Exxon station on Chain Bridge Road in Oakton, her cash register sends the information to Exxon Mobil's central computers. If she raises the price of gasoline a couple of pennies, chances are that Exxon will raise the wholesale price she pays by the same amount.

Through a password-protected Web portal, Exxon notifies Rezazadeh of wholesale price changes daily. That way the oil giant, which is earning about $3.3 billion a month, fine-tunes the pump prices at the franchise Rezazadeh has owned for 12 years.

Now, however, Rezazadeh says she cannot stay in business. Credit-card fees are eating her profit margins. Exxon, which owns the station land, last week handed Rezazadeh a new lease raising her rent about 30 percent over the next three years. She stuck a copy on the window of her station to show customers who are angry about soaring pump prices. Rezazadeh has told Exxon that she cannot make money with the rent that high. Her territory manager's reply, she said, was simple: When you go, leave us the keys.
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1593. TerraNova
11:40 AM EDT on May 25, 2008
12z GFS is now running.
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1592. Patrap
10:35 AM CDT on May 25, 2008
nola.com Link
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1591. ShenValleyFlyFish
3:34 PM GMT on May 25, 2008
Safety Lapses Raised Risks In Trailers for Katrina Victims

Formaldehyde Found in High Levels; 17,000 Say Homes Caused Illnesses

By Spencer S. Hsu
Washington Post Staff Writer
Sunday, May 25, 2008; Page A01

Within days of Hurricane Katrina's landfall in August 2005, frantic officials at the Federal Emergency Management Agency ordered nearly $2.7 billion worth of trailers and mobile homes to house the storm's victims, many of them using a single page of specifications.
This Story

Safety Lapses Raised Risks In Trailers for Katrina Victims
Formaldehyde: A Range of Standards
Three Types of FEMA Housing

Today, industry and government experts depict the rushed procurement and construction as key failures that may have triggered a public health catastrophe among the more than 300,000 people, many of them children, who lived in FEMA homes.
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1590. Blipvert
3:31 PM GMT on May 25, 2008
...And if you're really interested, this sorta thing runs in the family. The Palm Sunday Tornado that destroyed Dunlap in 1965 claimed the houses of most of my immediate family. My father took what I think are the only color pictures that survive of the aftermath of that event. I have posted the 43 year old pics here:


Now That's EF-4/EF-5 damage.
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1589. Drakoen
3:27 PM GMT on May 25, 2008
Good morning. Still unclear about where cyclogenesis will occur but the ECMWF, NOGAPS, and GFS hint development in the western Caribbean likely advected from the EPAC.
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1588. Blipvert
3:23 PM GMT on May 25, 2008
I just uploaded a few dozen pics of the damage around Windsor. Emergency crews/police have the area very well cordoned off, but I was able to get onto the Kodak property and take some pics of the area directly in the middle of the path of the tornado just before it tore through Windsor, after it hit the RV park where the solde fatality was recorded.

Pictures are at:


Here's a particulary interesting image- one tree that was standing left out of pretty much a razed field, with sheet metal squarely wrapped around one of the twisted branches:

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1587. KrazyKaneLove
3:13 PM GMT on May 25, 2008
why wednesday? is that when the development is supposed to occur according to gfs?
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1586. Patrap
10:13 AM CDT on May 25, 2008
No doubt,Patton had a sense of History and was a Avid reader of it.

He knew his role and never wavered on it. One has to respect a Man/General who Leads and Hit his Knee's every Night for Guidance doing it.Link
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1585. ShenValleyFlyFish
2:58 PM GMT on May 25, 2008
1568. Patrap

An excellent film.

As a member of a pacifist "sect" I treat the day as one of mourning for all the dead of all wars civilian & military. How many here can say that their childhood pastor began his service with a prayer for wisdom for "ALL those in authority" and thanks for "guidance to a Land where we are allowed to worship as we chose"?
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1584. Patrap
10:06 AM CDT on May 25, 2008
BarometerBob Show Link

Dont forget to join Barometer Bob for The 2008 Hurricane Preparedness Week will be held May 25th through May 31st.

Bob will be hosting "Hurricane Hollow's Hurricane Awareness Week" Internet Broadcasts each evening beginning at 8PM/ET on WRBN.Net with your host Barometer Bob Brookens and special guests.

Scheduled Guests

Sunday May 25 - Lew Fincher, from HurricaneConsulting.Net. You have seen him on the History Channel special about "Isaac's Storm" the 1900 Galveston Hurricane.
Monday May 26 - Jamie Rhome, Hurricane Specialist at the National Hurricane Center.
Tuesday May 27 - Bob Breck, Chief Meteorologist from WVUE-TV - Fox 8 in New Orleans, LA.
Wednesday May 28 - Laura Algeo, FEMA Region IV, National Flood Insurance Program.
Thursday May 29 - Eric Blake, Hurricane Specialist at the National Hurricane Center. We will also have Butch Loper, Emergency Operations/Civil Defense Director for Jackson County, MS.
Friday May 30 - Leslie Chapman-Henderson, Director of FLASH.Org.
Saturday May 31 - Michelle Jantz Manager, Program Management and Support Preparedness and Health and Safety Services from the American Red Cross.

Hurricane Hollow's Eye on the Storm June 1st Broadcast

Bob will have special guests, callers and you can join us in Storm Chat!
My guests include:
Spokeperson from 511 the Traffic Information Portal.
Gary Padgett, from the Tropical Cyclone Summeries.
And more! Stay tuned for more information on the 8 nights of broadcasts from www.WRBN.Net!

Come join in chat for a full week of Hurricane Prepardness
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1583. StormJunkie
3:00 PM GMT on May 25, 2008

It also helps to look at the different variables that models forecast jm. Ex being, vorticity, upper level winds, etc.

These are some pretty good video tutorials on using and navigating several of the model pages.

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1581. juniormeteorologist
2:52 PM GMT on May 25, 2008
Thanks again patrap! I just looked at that model also...

TerraNova, I read that statement, and i highly think that there is a good chance this will become the first system of the year.

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1580. Weather456
10:42 AM AST on May 25, 2008
U may also like to take a look at this QuikSCAT pass. It shows a circulation near 85W-90W north of 10N. Likely induced by a passing tropical wave.
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1579. IKE
9:48 AM CDT on May 25, 2008
1574. juniormeteorologist 9:46 AM CDT on May 25, 2008
I was just looking at the GFS models, and what are these blob that seems to be developing? Please explain to me!

It's moisture...too far in advance to know if it's anything more.
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1578. TerraNova
10:48 AM EDT on May 25, 2008
I was just looking at the GFS models, and what are these blob that seems to be developing? Please explain to me!

Refer to post #1554.
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1577. Patrap
9:48 AM CDT on May 25, 2008
UNYSIS GFSx Day 10 4JUNE 0Z Surface Link
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1576. juniormeteorologist
2:48 PM GMT on May 25, 2008
thanx patrap!
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1575. Patrap
9:46 AM CDT on May 25, 2008
Its a Model run..nothing more.Just a tool for insight as to what MAY occur.
Do not use for Planning Purposes.

Rely on the NHC,NWS and your Local NWS office for official Forecast Products
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1574. juniormeteorologist
2:45 PM GMT on May 25, 2008
I was just looking at the GFS models, and what are these blob that seems to be developing? Please explain to me!

Monday June 02

Monday June 09
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1573. TerraNova
10:37 AM EDT on May 25, 2008
So, folks are we FINALLY going to see a Carib storm at some point this week or aren't we? Any reply would be greatly appreciated!!!

LOL, that a very good question! Honestly, it's impossible to tell. I suppose the fact that some NWS forecasting offices have begun to notice, and (more over) that more models have begun to catch on is an indication that the possiblity of an Atlantic storm is rising. But how likely this scenerio is is very to tell. Right now all we can rely on are models that can't seem to make up their minds and climatology. Again, only time will tell. Wednesday will be very interesting in the tropics.
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1572. Patrap
9:36 AM CDT on May 25, 2008
One cant see the Future.
But one can Prepare.

Hurricane Preparedness Week Starts Today
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1571. Weather456
10:33 AM AST on May 25, 2008

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1569. Patrap
9:18 AM CDT on May 25, 2008
GOES-12 Atlantic Ocean View (Updated ~3 hours) Link
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1568. Patrap
9:08 AM CDT on May 25, 2008
The opening monologue, delivered by Scott with an enormous American flag behind him, remains an iconic and often quoted image in film. Despite the rise of the Vietnam protest movement and a decline in interest in World War II movies, the film became a success and an American classic.[2]

In 2003, Patton was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant".

Gee, How deflating. I liked Patton and George C. Scott.

A Oscar Award winning Actor and Best Film for that Year,71 I believe.
A tribute to WW-2 Vets.

Thanx MLC.

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1567. franck
2:01 PM GMT on May 25, 2008
1555...not against Memorial Day but your post has little to do with history. It's a movie, and a dead actor.
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1566. ClearH2OFla
10:02 AM EDT on May 25, 2008
Good Morning Everyone. Question, say a mention of a possible storm heading toward west coast of Florida. Never could find anything (model run) on that. Can anyone confirm or deny. Thanks in advance
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1565. Patrap
9:03 AM CDT on May 25, 2008
The Planets getting bigger by the minute in da window I bet..

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1564. StormJunkie
1:57 PM GMT on May 25, 2008
Morning all :~)

T- 9hrs 51 min Pat!
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1563. TerraNova
9:48 AM EDT on May 25, 2008
Here's a real great guide for the tropical weather forecaster from the Navy/NRL:
Tropical Cyclone Forecasters' Reference Guide
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1561. Patrap
8:46 AM CDT on May 25, 2008
No Final Nudge Needed for Phoenix
05.25.08, 9:30 a.m. EDT -- NASA's Phoenix Mars Lander will reach Mars this evening with no further adjustments to its flight path. The first possible time for confirmation that Phoenix has landed will be at 7:53 p.m. Eastern Time today.
Read more
› Next briefing: 6 p.m. Eastern, NASA TV on the Web Link
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1559. FloridaRick
8:21 AM EST on May 25, 2008
From all of us that have served, we thank you for your support! God Bless
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1558. Weather456
8:51 AM AST on May 25, 2008
Hurricane Prepardness Week; The Tropics; Hurricane Journal Part 1
Member Since: December 31, 1969 Posts: Comments:
1557. FLWeatherFreak91
9:12 AM EDT on May 25, 2008
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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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