Killer tornadoes rip Iowa, and Minnesota; tropical depression possible late this week

By: Dr. Jeff Masters , 2:08 PM GMT on May 26, 2008

The 2008 Memorial Day Weekend tornado outbreak will continue to hammer the U.S. today, even as residents from Iowa and Minnesota clean up from the devastating tornadoes that killed eight people Sunday afternoon. A mile-wide tornado plowed through Parkersburg, Iowa between 5pm and 6pm CDT yesterday, killing five people in that city, and two in nearby New Hartford. It was the deadliest tornado in Iowa in more than 40 years. The tornado passed just north of the airport in Waterloo, Iowa, which recorded sustained winds of 64mph, gusting to 94 mph at 5:37pm CDT. Damage appeared to be at least EF-4 in photos I saw, and possibly EF-5 (over 200 mph). In Minnesota, another powerful twister killed at least one person and injured 9 in the Minneapolis suburb of Hugo.

Figure 1. Satellite image of the supercell thunderstorms that spawned the Parkerburg, Iowa and Hugo, Minnesota tornadoes on May 25, 2008.

The slow-moving low pressure system responsible for all the mayhem began in Colorado on Thursday, when the Storm Prediction Center (SPC) recorded 48 reports of tornadoes, including the EF-3 mile-wide twister that killed one person in Windsor, Colorado. On Friday, an additional 63 tornado reports occurred, mostly in Kansas. The tornado that hit Quinter, Kansas on Friday was the eighth violent EF-4 tornado of the year. Also on Friday, two people were killed in Cairo, Kansas when a tornado smashed a car trying to flee the storm. If you want to see why one should not try to escape a tornado in a car, take a look at what the tornado did to the car. Saturday was relatively quiet, with only 13 tornado reports, but Sunday's tally of 43 brought the 4-day total from the 2008 Memorial Day weekend outbreak to a remarkable 157 tornado reports. Some of these tornado reports are undoubtedly of the same tornado, so the actual number of tornadoes for the 4-day outbreak may be less than 150. BBC has some awesome aerial footage of the weekend tornadoes.

Figure 2. Radar reflectivity image (top) of the May 25, 2008 Parkersburg, Iowa tornado. The position of Parkersburg is marked by a circle with a cross in the middle. 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.

Figure 3. Radar reflectivity image (top) of the May 25, 2008 Hugo, Minnesota tornado. The position of Hugo is marked by a circle with a cross in the middle. 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. We've also saved a 12-frame radar animation of the Hugo cell, thanks to wunderground member Todd S.

Tallying up the numbers
The death toll from Sunday pushes this year's tornado deaths to 111, the most since 1998, when 130 were recorded. Assuming that the Parkersburg, Iowa tornado was an EF-4 or EF-5, there have been nine violent EF-4 or EF-5 tornadoes this year. This is the most since 1999, when 13 such twisters were recorded. The total number of tornadoes this year is approaching 1100, and we may challenge the all time record for tornadoes in a year of 1817, set in 2004. Could this be a sign of climate change? No, I don't think so, and I'll explain why in a blog later this week.

Severe weather forecast
Severe weather will pound the U.S. again this Memorial Day, with the main action expected to stretch more than halfway across the country--from Texas to New York. NOAA's Storm Prediction Center has placed much of Kansas, Oklahoma, and the Texas Panhandle 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 in Iowa and Minnesota. The Weather Underground Severe Weather page and Tornado 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. After today, it appears the severe weather outbreak will finally diminish, with only a slight risk of severe weather expected Tuesday, and no severe weather expected Wednesday.

Possible development in the Western Caribbean or Eastern Pacific late this week
For the past 3-6 days, our most reliable global computer weather forecast models have been predicting the development of a low pressure system near or over Central America by Friday of this week. Given the persistence in the models in developing this low, we need to be alert to the possibility of a tropical depression forming in either the Western Caribbean or Eastern Pacific, on either side of Costa Rica and Nicaragua. It is uncertain which ocean basin such a storm might form in, and whether or not there will be a tropical wave around to help kick off development. It may be that the low pressure region will stay anchored over land south of the Yucatan Peninsula, preventing any development. This is the solution preferred by the ECMWF model in its last few runs. However, the GFS, NOGAPS, and Canadian models all predict a tropical depression might form in the Western Caribbean near Mexico's Yucatan Peninsula. In contrast, the UKMET shows development in the Eastern Pacific, on the Pacific side of Central America. Climatologically, May tropical storms are much more common in the Eastern Pacific than the Western Caribbean, so we should not discount the UKMET solution, even though it is an outlier. All five models predict that the Central American low pressure area will move northward towards the Gulf of Mexico, and wind shear may fall enough to allow a tropical depression to form should the low's center emerge over water. I'll be posting daily updates on the situation this week.

Jeff Masters

Wedge Tornado (MikeTheiss)
A large and violent wedge tornado near Quinter, Kansas. Photo Copyright Mike Theiss
Wedge Tornado
Wallcloud near Lacrosse, Kansas (MikeTheiss)
Photo of a wallcloud crossing road near lacrosse, Kansas on May 25, 2008. Photo copyight Mike Theiss
Wallcloud near Lacrosse, Kansas
Storm Damage (CAPEdcrusader)
These are pictures taken of the storm that went through Forest Lake / Hugo, MN. The tornado passed 3 miles south of us, but we got a pretty vicious shot of hail for about 15 minutes straight. The pictures of bldg damage are west of the worst tornado damage, probably where the funnel cloud was just about to reach the ground.
Storm Damage

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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1359. TerraNova
11:16 AM EDT on May 27, 2008
1355. nrtiwlnvragn 11:15 AM EDT on May 27, 2008

Member Since: December 31, 1969 Posts: Comments:
1358. scottsvb
3:15 PM GMT on May 27, 2008
cchs did... and there is none there. 1 may begin to form later tonight..but currently only midlevel vortxes!
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1357. Michfan
10:13 AM CDT on May 27, 2008


Yeah scott brings up a good point. THe 850 vort on the SW Caribbean low doesnt show up well so im not entirely convinced its hit the surface yet. The elongated low in the EPac on the other hand does.
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1356. Patrap
10:14 AM CDT on May 27, 2008
Jeff Masters Entry on Quikscat and ASCAT Data Link

QuikSCAT now has help. An important new source of QuikSCAT-like data has been made available by the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT). They launched their first polar-orbiting satellite, Metop-A, in October 2006, and declared the satellite ready for routine operations as of May 2007. This satellite carries a scatterometer called ASCAT which, like QuikSCAT, measures the winds at the ocean surface. ASCAT doesn't "see" the Earth's surface as well as QuikSCAT can--ASCAT sees chunks of the surface 25 km by 25 km, while QuikSCAT has a resolution twice as good--12.5 km. In addition, ASCAT only sees 60% of what QuikSCAT sees of the Earth's surface--QuikSCAT sees a swath of ocean 1800 km wide, while ASCAT sees two parallel swaths 550 km wide, separated by a 720 km gap. I found it frustrating to use ASCAT much this hurricane season, since it seemed that the passes missed the center of circulation of a storm of interest about 75% of the time.
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1355. nrtiwlnvragn
11:14 AM EDT on May 27, 2008
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1354. seflagamma
11:10 AM AST on May 27, 2008
good morning my friends; haven't really read back yet but last time I was here on Saturday I know the models were predicting a possible invest this week... is something out there?

I'm home today so should get a chance to check in and out during the day. Hope Dr master's sets up a new thead soon.

So an invest yet??? (will go read back now) LOL
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1353. Patrap
10:12 AM CDT on May 27, 2008
ASCAT validation with buoy and QuikSCAT data
File Format: PDF/Adobe Acrobat - View as HTML
For global scales, the quality of ASCAT data is investigated using .... ASCAT and QuikSCAT data coherency is also investigated based on the approach ... - Similar pages
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1352. TampaSpin
11:11 AM EDT on May 27, 2008
Scott no one said a SL was there i believe most have stated one is developing as you just stated.
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1349. Patrap
10:11 AM CDT on May 27, 2008

Press Releases

June 13, 2007
ECMWF operational weather forecasts now use IASI and ASCAT data
Reading/Darmstadt/Toulouse – IASI radiance and ASCAT surface wind data, both derived from instruments on board of Metop-A, are operationally used in the European Centre for Medium-Range Weather Forecasts (ECMWF) forecasting system - just over 12 weeks after the first data were disseminated to Numerical Weather Prediction centres and only 8 months after the launch of the Metop-A satellite on 19 October 2006. Link
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1348. cchsweatherman
11:07 AM EDT on May 27, 2008
1344. HouseofGryffindor 11:06 AM EDT on May 27, 2008
cchs how would the blob be steered when it is in the gulf? Would it keep moving north or is there another mechanism that could turn it?

Like I have been stating, it would be just pure speculation beyond the point when any system would reach the Northwestern Caribbean, but we would need to watch any troughs in the northern US very closely to see what effect they would have on the Atlantic ridge. Thats about as much as I can tell you without going into speculation.
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1347. scottsvb
3:09 PM GMT on May 27, 2008
There is no circulation center in the SW carribean...there are weak mid-level lows... A surface low should begin to form later tonight and into Weds.
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1346. TerraNova
11:07 AM EDT on May 27, 2008
Does anybody have a link to ASCAT data?
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1345. Patrap
10:06 AM CDT on May 27, 2008
The Ouikscat database problem isnt related to the On Orbit Operation or Health of the Actual Spacecraft
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1342. nash28
11:05 AM EDT on May 27, 2008
It figures. Tropics begin waking up from the six month nap. QS craps out already...
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1341. nrtiwlnvragn
11:04 AM EDT on May 27, 2008
Hope they get this fixed:


Noticed update on quikscat page has not updated since May 27 02:42

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1340. cchsweatherman
10:51 AM EDT on May 27, 2008
Many people have been doubting that this entire system will be moving northward like the models have shown. Here is an explanation for why this entire system will INDEED move northward.
Right now, there is an upper level trough that has dug into the Northwest Caribbean as a result of the front that moved through South Florida on Sunday. The upper level trough has been creating some very high wind shear in the Northwest Caribbean (around 40kts.).

During the next 24 to 48 hours, this upper-level trough will exit the Northwest Caribbean and move into the Northern Atlantic. This will lift the entire system out from the Southwest Caribbean and Eastern Pacific and into the Northwest Caribbean and over Central America. During this time, an upper-level high (better known as an anticyclone) will develop over the system. This will cause a rapid drop in shear over the Northwest Caribbean by late week.

Beyond that, not much can be gleened based upon the current conditions as to what will happen to any system that would develop and move into the Northwestern Caribbean.
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1339. Patrap
10:01 AM CDT on May 27, 2008
UNYSIS GFSx Day-8 4June 0Z surface Link
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1338. TampaSpin
10:50 AM EDT on May 27, 2008
A thing of note the Pacific low should enhance the Carribean low on a Northerly direction into a more favaorable environment.
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1337. Patrap
9:52 AM CDT on May 27, 2008
Why thanks Tampaspin,..My Service years were fine ones,and it was an Honor to Serve the Nation.

LSU ESL site.Link

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1336. weathermanwannabe
8:31 AM CST on May 27, 2008
Good Morning Folks.........Agree with all of the comments as to the potential E-Pac/Central AM system with regard to needed persistence, and, only one of those areas "fully" developing, if at all, due to the close proximity......Looks like a pretty small window of opportunity on the Atlantic side right now (with some shear just to the North of the "blob" near Panama).......
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1335. nash28
10:51 AM EDT on May 27, 2008
Any wind obs down near that Low?
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1334. cchsweatherman
10:49 AM EDT on May 27, 2008
You are correct Tampa. There is a surface low developing and strengthening in the Southwest Caribbean right now.
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1333. cchsweatherman
10:34 AM EDT on May 27, 2008

Now, I have indicated where I have observed two surface lows at the present time. Both are quite well-defined on satellite imagery and both have some deep convection developing in association with them. There is something that I have observed that has impressed me about the Southwest Caribbean low that noone else has mentioned to my surprise. Notice how there is, what appears to be, a feeder band attached to the eastern side of the low feeding in deep tropical moisture from the Pacific over Panama and into the system. This is very much a sign that the Southwest Caribbean low is currently the stronger low. Now, to the Pacific low, it remains quite broad, but definitely closed. There is a wide expanse of heavy showers and storms encircling the southern portion of the low, but convection is absent from the northern portion. It may just be too broad to start any significant tropical development within the next 48 hours. If the Pacific low consolidates, then we could have some battle over which low wins out.
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1332. TampaSpin
10:45 AM EDT on May 27, 2008
Gang im not a Met but it sure looks like a SL is developing in the SW Carrib.
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1331. TampaSpin
10:39 AM EDT on May 27, 2008
Patrap thank you for serving for me and our country. Hope you had a great Veterans Day.
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1330. Patrap
9:36 AM CDT on May 27, 2008
Area forecast discussion
National Weather Service New Orleans la
354 am CDT Tuesday may 27 2008

Regarding model generation of tropical low from western Caribbean
Sea next week...the models continue to flip-flop on this solution
with GFS now showing some energy meandering over Yucatan Peninsula
while a separate low peels off and deepens while moving into the
Florida Peninsula next week. European model (ecmwf) shows a similar split but then
decays both circulations rather quickly with little fanfare. This
appears to be the start of a season of model idiosyncracies in the
tropical latitudes of the model domain. These solutions...given
the distance in time...are being discounted beyond Monday.

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1328. nrtiwlnvragn
10:31 AM EDT on May 27, 2008
1294. cchsweatherman

You can monitor this island of the east coast of Nicaragua San Andres Isla its located at 12-35N 081-43W.
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1327. Michfan
9:29 AM CDT on May 27, 2008

If the convection in Central Africa stays where its at and propogates westward i think we could start to see the ITCZ shift northward in the next week or two.
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1326. TampaSpin
10:26 AM EDT on May 27, 2008
Michfan you are correct sheer does need to drop.
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1325. KrazyKaneLove
2:23 PM GMT on May 27, 2008
NE, nope, but he was "wicked upset" during 2004, having to shutter up the house with no friends or family to help..there is a price to pay for beautiful weather..trying to explain the woes of a hurricane to his brothers in N.E. was almost comical to hear, needless to say, they gave him a hard he always boasts about the temperatures to them.
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1324. sporteguy03
2:25 PM GMT on May 27, 2008
Just watch Eyewitness News at 12 then Brian will show a Sat pic.
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1323. Michfan
9:24 AM CDT on May 27, 2008
The low in the SW Caribbean is going to need shear to drop a bit.
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1322. TampaSpin
10:24 AM EDT on May 27, 2008
Here is the latest Visible.
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1321. catastropheadjuster
2:20 PM GMT on May 27, 2008
Good Morning ev1. So how things looking tropical wise. I will be in and out. Have to rip carpet out of a bass boat and put new in. That's my speciality.
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1319. NEwxguy
2:20 PM GMT on May 27, 2008
NP, Krazy,I'm sure your husband doesn't miss the winters up here.
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1318. nash28
10:20 AM EDT on May 27, 2008
Gotta run and fix some wireless issues here in the hospital for a bit. I will be checking Vis as soon as I get a chance.
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1317. TampaSpin
10:19 AM EDT on May 27, 2008
Looking at the newest visible that just came in, in my opinion we have a devlopoing Surface low in the SW Carribean forming.
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1316. KrazyKaneLove
2:09 PM GMT on May 27, 2008
yeah Ike, I was was just eyeballing that..always watch out there this time of year for sneaky
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1315. Michfan
9:11 AM CDT on May 27, 2008

Bookmark for all of your tropical link needs.
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1314. KrazyKaneLove
2:05 PM GMT on May 27, 2008
sorry, NE, I was just trying to provide some levity to the blog during slow time, now things have picked up again..ty for your reply. P.S. my husband is from Framingham, go Pats, sox, and especially, Celtics!
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1313. Michfan
8:52 AM CDT on May 27, 2008
The convection in the SW Caribbean needs to persist through the day. It puttered out a bit last night. You can see the low level circulation pretty well on the visible loop.

850mb vorticity is showing the elongated low in the Pacific very well. The low in the SW Carribean not as well.

Current wind shear shows an anticyclone developing over the low the EPac and the SW Carribean low is over approximately 20-30 knots of wind shear but i believe that is forecast to lower over the next few days.

If any of these make it to the east coast of the Yucatan it will enter a very favorable wind shear profile to develop in.
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1312. hurricane23
10:07 AM EDT on May 27, 2008
1310. nash28 10:06 AM EDT on May 27, 2008
As we have all learned over the year, persistence is key.

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1311. IKE
9:04 AM CDT on May 27, 2008
Anyone notice the spin east of SE FL.?.......

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1310. nash28
10:04 AM EDT on May 27, 2008
As we have all learned over the year, persistence is key.
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1309. hurricane23
10:03 AM EDT on May 27, 2008
JP from the view at those maps the caribbean has the best convergence at the moment.Upper level winds are not to favorable right now but they may slacken off a bit by late week.
Member Since: December 31, 1969 Posts: Comments:

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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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