NWS: IA Tornado Season started big, ended with a whimper

News, Weather

November 25th, 2011 by Ric Hanson

A Meteorologist with the National Weather Service in Johnston says there were 50 tornadoes in the state this year, which is just above the 30-year average of 47 tornadoes. Altogether, 16 people were injured by the events, but there were no fatalities. Craig Cogil says the season started-up rapidly in March and early April, but lost steam as the season progressed. Cogil says two significant tornado days occurred early in the season, on March 22nd over southwest to south central Iowa during the late afternoon and evening hours. The event produced 8 tornadoes over a 2-hour period, including an EF-2 in Madison County, which caused property damage to several farms and one home.  EF-2′s produced winds of 111-to 135 miles per hours.

An event on April 9th was the largest outbreak of tornadoes for one day across Iowa since May, 2004, when 20 tornadoes twisted their way across the state. The event started during the mid-evening hours when the first tornado, an EF-3 (with winds of 136-to 165-mph), hit Mapleton, in Monona County. Nearly 100 homes were destroyed and many other severly damaged in a 12-to 15-block area. The event resulted in 14 injuries and 500 residents being displaced. Several other tornadoes formed over the next several hours that day, from west central into north central Iowa, including one that tracked more than 29-miles from northern Sac through southeastern Buena Vista and western Pocahontas Counties.  It had the distinction of being 1.5-miles wide at times, and produced numerous “Satellite” tornadoes, which tracked around the main tornado. One of the satellites was an EF-4 (winds from 166- to 200-mph). It destroyed a farmstead and tossed a combine nearly 300-yards.

Two significant tornado events occurred in May, including two on May 11th that hit the town of Lenox within a span of 5-minutes. Both tornadoes were rated as EF-1′s, producing winds of 86 to 110-miles per hour. Both tornadoes caused extensive roof and tree damage. The other tornado event in May was in eastern Iowa’s Howard County.

The remainder of the season saw 10 more tornadoes occurr on six different days. The most occurred on June 20th, when four twisters were observed. The last tornado of the season was on July 11th. It caused extensive damage in portions of central and eastern Iowa. The fact the last tornado was confirmed on that date marked the earliest cessation of tornadic activity in the state since reliable records started in 1980, beating the previous earliest cessation record set on July 24, 1992.

For more detailed info., surf to www.weather.gov/desmoines.