Killer tornadoes smash Iowa and Minnesota

An exceptional tornado outbreak continues to hammer the U.S. tonight, in what has been an extraordinary year for tornadoes. A mile-wide tornado plowed through Parkersburg, Iowa this afternoon, killing at least five people and injuring 15, according to KCRG. 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 this afternoon.


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

A slow-moving low pressure system that began in Colorado on Thursday spawned 48 reports of tornadoes Thursday, 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. The last year that had more violent tornadoes was 1999, when 13 such twisters were recorded. 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 (so far) of 37 has brought the 4-day total to a remarkable 150+ 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.



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.

Severe weather forecast
Severe weather will pound the U.S. again Memorial Day, with the main action expected to stretch more than halfway across the country--from Colorado to New York. NOAA's Storm Prediction Center has placed central Kansas 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.

I'll have an update Monday morning, including a look at the tropics, where the computers models persist in predicting a tropical storm may form in the Western Caribbean or Eastern Pacific late this week.

Jeff Masters