Dr. Jeff Masters' WunderBlog

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

Posted by: Dr. Jeff Masters, 13:23 GMT le 23 mai 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

()

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

Categories: Tornado

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1251. Stormchaser2007 21:36 GMT le 24 mai 2008
This thing dose not cease to impress. Link Member Since: 9 juin 2007 Posts: 4 Comments: 15248

1252. zoomiami 21:38 GMT le 24 mai 2008
This is some of the most amazing weather footage I have seen - to see the tornado actually generating in real time is unbelievable Member Since: 13 août 2007 Posts: 10 Comments: 4064

1253. Cavin Rawlins 21:38 GMT le 24 mai 2008
The 12Z ECMWF is predicting development in the EPAC similar to the CMC, but the system crosses central America and ends somehwere just offshore the Yucatan Peninsula. Member Since: 24 juillet 2005 Posts: 407 Comments: 19076

1254. nash28 21:38 GMT le 24 mai 2008
Starting to weaken.... Went from around 50,000ft now down to 40,000ft. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1255. nash28 21:39 GMT le 24 mai 2008
Live stream over... Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1256. Zachary Labe 21:40 GMT le 24 mai 2008
Yes the cell is beginning to become not as organized on the reflectivity radar, the hook echo is not as easy to detect. Member Since: 14 décembre 2007 Posts: 253 Comments: 14299

1257. Stormchaser2007 21:40 GMT le 24 mai 2008
Would not be surprised to see an EF3/4 on the ground if they were still up there and also if the doggoned tornado wasn't so embedded in rain. Member Since: 9 juin 2007 Posts: 4 Comments: 15248

1258. Stormchaser2007 21:41 GMT le 24 mai 2008
From before.... Link Member Since: 9 juin 2007 Posts: 4 Comments: 15248

1259. SouthDadeFish 21:41 GMT le 24 mai 2008
Ok I was watching fox news and they keep saying four miles across... I assume they are talking about the wall cloud being four miles across rather than the funnel, correct? I have never heard of a tornado being anywhere close to four miles across so im pretty confused... Nevertheless, this situation is very scary. Member Since: 12 août 2007 Posts: 11 Comments: 2417

1260. TerraNova 21:43 GMT le 24 mai 2008
The feed's still up...12th tornado just dropped. Member Since: 30 juillet 2007 Posts: 76 Comments: 4058

1261. SouthDadeFish 21:43 GMT le 24 mai 2008
18Z GFS starting to come out now also. Member Since: 12 août 2007 Posts: 11 Comments: 2417

1262. TerraNova 21:44 GMT le 24 mai 2008
THe 18z NAM develops a low in the SW Caribbean. Member Since: 30 juillet 2007 Posts: 76 Comments: 4058

1263. Stormchaser2007 21:44 GMT le 24 mai 2008
The feed's still up...12th tornado just dropped. Wheres the feed from?? Member Since: 9 juin 2007 Posts: 4 Comments: 15248

1264. TerraNova 21:46 GMT le 24 mai 2008
KWTV News 9 feed. You just missed the 12th LOL but i'm sure there will be another! Member Since: 30 juillet 2007 Posts: 76 Comments: 4058

1265. Stormchaser2007 21:50 GMT le 24 mai 2008
Tampa your link didn't work. It just shows a blank screen. Member Since: 9 juin 2007 Posts: 4 Comments: 15248

1266. weathersp 21:51 GMT le 24 mai 2008
Thanks! Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

1267. weathersp 21:52 GMT le 24 mai 2008
This is even better they have chasers on the ground! Member Since: 14 janvier 2007 Posts: 17 Comments: 4112

1268. FLWeatherFreak91 22:01 GMT le 24 mai 2008
Who if the current GFS plays out Tampa is s-k-r-e-w-e-d Member Since: 1 décembre 2006 Posts: 2 Comments: 3458

1269. Stormchaser2007 22:01 GMT le 24 mai 2008
Statement as of 4:44 PM CDT on May 24, 2008 ... A Tornado Warning remains in effect until 515 PM CDT for southeastern Garfield County... At 444 PM CDT... a large... violent tornado was located 3 miles southeast of Douglas... moving northeast at 13 mph. Radar indicates another circulation may be forming close to Highway 74 5 to 7 miles south of Covington. Baseball hail was reported 1 mile east of Douglas at 444 PM. * Locations in the warning include Covington... Douglas and Hayward. This tornado may be obscured by rain and may not be visible. Abandon Mobile homes and vehicles. If possible... move to a basement or storm shelter. Otherwise move to an interior room or hallway on the lowest floor. Stay away from windows. This is an extremely dangerous and life threatening situation. If you are in the path of this large and destructive tornado... take cover immediately. A basement or storm shelter is best. Otherwise... take cover in an interior closet or bathroom away from outside walls and windows. Cover your head with pillows and blankets. For the Current Cell Member Since: 9 juin 2007 Posts: 4 Comments: 15248

1270. BahaHurican 22:05 GMT le 24 mai 2008
1158. moonlightcowboy 3:30 PM EDT on May 24, 2008 Yeah, this caught my eye a couple of hours ago, so that I posted the same image . I suppose by next weekend that right-most wave will be in the CAR, which is about when I'll seriously start expecting things to fire . . . Member Since: 25 octobre 2005 Posts: 19 Comments: 17620

1271. ClearH2OFla 22:07 GMT le 24 mai 2008
Can some one please post the model page link i keep hearing about the GFS model and a Storm but cant find it. THank you.

1272. nash28 22:08 GMT le 24 mai 2008
FL- The 18z GFS isn't done yet.... Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1273. FLWeatherFreak91 22:08 GMT le 24 mai 2008
GFS Stormjunkie's page is great and easy to navigate Member Since: 1 décembre 2006 Posts: 2 Comments: 3458

1274. nash28 22:08 GMT le 24 mai 2008
Does anyone have the live feed we were watching from earlier??? CNN dropped it. The News9 feed doesn't work. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1275. SouthDadeFish 22:09 GMT le 24 mai 2008
Here's the link to the GFS and other models. Link Member Since: 12 août 2007 Posts: 11 Comments: 2417

1276. nash28 22:10 GMT le 24 mai 2008
FL- That's not the GFS. You linked the OK radar tornado:-) Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1277. nash28 22:10 GMT le 24 mai 2008
18z GFS is still running. Only at 96hrs. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1278. SouthDadeFish 22:11 GMT le 24 mai 2008
FL thats the 12Z GFS run and is over 200 hours out. Member Since: 12 août 2007 Posts: 11 Comments: 2417

1279. Stormchaser2007 22:11 GMT le 24 mai 2008
Does anyone have the live feed we were watching from earlier??? CNN dropped it. The News9 feed doesn't work. Yeah same for me. Member Since: 9 juin 2007 Posts: 4 Comments: 15248

1280. nrtiwlnvragn 22:12 GMT le 24 mai 2008
NEWS9 link still works for me. Member Since: 23 septembre 2005 Posts: 11 Comments: 8922

1281. FLWeatherFreak91 22:13 GMT le 24 mai 2008
1278. SouthDadeFish 6:11 PM EDT on May 24, 2008 Hide this comment. FL thats the 12Z GFS run and is over 200 hours out. I know, someone was asking about the GFS Storm so I showed them the most current complete model run which included the Storm Member Since: 1 décembre 2006 Posts: 2 Comments: 3458

1282. SouthDadeFish 22:13 GMT le 24 mai 2008
GFS starts to form a low in the W Caribbean at 102 hours out. Member Since: 12 août 2007 Posts: 11 Comments: 2417

1283. nash28 22:14 GMT le 24 mai 2008
And I wouldn't get too excited over that run... If come Tuesday, the GFS still shows a system making that kind of approach, with tighter millibars, then I'll get excited. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1284. stormhank 22:14 GMT le 24 mai 2008
Link 18Z GFS 108hrs Member Since: 8 septembre 2005 Posts: 0 Comments: 1375

1285. SouthDadeFish 22:15 GMT le 24 mai 2008
1281. Okay sorry just wanted to make sure you knew :~) That would be quite an interesting scenario as I have never seen a storm stall on the coast and then move back over the ocean to make landfall somewhere else lol Member Since: 12 août 2007 Posts: 11 Comments: 2417

1286. ClearH2OFla 22:17 GMT le 24 mai 2008
Thanks everyone

1287. Stormchaser2007 22:17 GMT le 24 mai 2008
Uhhhh.... theres the same rotation that produced the Greensburg tornado on this storm. Link Member Since: 9 juin 2007 Posts: 4 Comments: 15248

1288. SouthDadeFish 22:19 GMT le 24 mai 2008
Wow! that mesocyclone even has an eyelike feature. I've never seen that before. The channel 9 feed shows it. Member Since: 12 août 2007 Posts: 11 Comments: 2417

1289. WPBHurricane05 22:22 GMT le 24 mai 2008
You must have Internet Explorer to watch the Channel 9 feed. Member Since: 31 juillet 2006 Posts: 55 Comments: 7897

1290. Smyrick145 22:26 GMT le 24 mai 2008
Nash, I live in Oklahoma City and it has been on live for the last 2 hours. There is a 2 1/2 mile funnel cloud that has been spawning tornadoes left and right. Were not talking about the same twister dropping down in the same area either. It is a truly amazing site. It his heading towards Stillwater/Ponca City area. Member Since: 30 septembre 2006 Posts: 0 Comments: 14

1291. WPBHurricane05 22:26 GMT le 24 mai 2008
Tornado Vortex Signature in a storm headed toward Deerfield Beach. Link Member Since: 31 juillet 2006 Posts: 55 Comments: 7897

1292. Drakoen 22:33 GMT le 24 mai 2008
the GFS 18z wants to develop the EPAC low and the Caribbean low. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

1293. IKE 22:33 GMT le 24 mai 2008
Drak...has it done that on the earlier runs today? Haven't had time to look... Member Since: 9 juin 2005 Posts: 23 Comments: 37044

1294. Drakoen 22:36 GMT le 24 mai 2008
1293. IKE 10:33 PM GMT on May 24, 2008 Drak...has it done that on the earlier runs today? Haven't had time to look... Not it hasn't. I have value the 00z runs and the 12z runs more than the 06z runs and 18z runs. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

1295. nash28 22:36 GMT le 24 mai 2008
Does anyone have another live feed OTHER THAN News9 for this??? It will not work for me. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1297. WPBHurricane05 22:37 GMT le 24 mai 2008
Does anyone have another live feed OTHER THAN News9 for this??? It will not work for me. Are you using Firefox? Try internet explorer. Member Since: 31 juillet 2006 Posts: 55 Comments: 7897

1298. SouthDadeFish 22:37 GMT le 24 mai 2008
The GFS looks like it combines the E Pac low and the W Carib low... Member Since: 12 août 2007 Posts: 11 Comments: 2417

1299. nash28 22:38 GMT le 24 mai 2008
Looks like at 216hrs the GFS has slowed down the CB Low. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

1300. Drakoen 22:38 GMT le 24 mai 2008
Well I know why the GFS 18z is showing the storm in the EPAC at least I know why it has it so strong. Jp, the 00z and the 12z runs take in more real time data than the 06z and 18z run. Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

1301. nash28 22:39 GMT le 24 mai 2008
I am using IE. IE 6. It's an issue with the object in Advanced Prop... Trying to fix it. Member Since: 11 juillet 2005 Posts: 190 Comments: 16972

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