Oskaloosa.com

May 23, 2013

Officials release storm survey results

MATT MILNER
CNHI

DES MOINES — A trio of tornadoes broke a nearly year-long streak without a twister in Iowa, officials have confirmed.

Severe weather broke out in Iowa earlier this week, part of the same system that caused lethal storms in Oklahoma. The storms on Sunday caused three tornadoes embedded in a much larger area of straight line winds.

None of the tornadoes was particularly strong. One was an EF0, the weakest type of tornado, with peak winds of 75 mph. The other two were both EF1 tornadoes with winds of 100 mph and 90 mph, respectively.

Comparatively, Monday's deadly tornado in Oklahoma has been rated an EF5 with winds over 200 mph.

The first tornado was southwest of Adel and was only on the ground for 1.5 miles. The evidence for a tornado, as opposed to regular storm winds, was weak initially. None of the evidence (spotter reports, radar, photos and survey results) taken individually would have supported a conclusion that a tornado had hit. Assessment as a whole, though, allowed experts to conclude a weak tornado formed amid winds that were nearly as strong as the tornado itself.

The first tornado was in open fields and did no damage. Both of the others hit structures. The second tornado formed east southeast of Dallas Center and was on the ground for 1.4 miles. A home on 250th Street near Dallas Center sustained damage.

The third tornado was on the ground the longest, with a path of five miles. It formed 2.5 miles south southeast of Slater and ended two miles south southeast of Huxley.

Of the three tornadoes, this was the one best documented. Radar showed “a very compact circulation,” according to the National Weather Service. Witnesses and law enforcement dashboard video also supported the conclusion of a tornado.

The worst damage from that tornado was the loss of a living room roof on a manufactured home.