Hail and Damaging Winds in Iowa, August 24, 1998

A very unstable airmass was located over Iowa with dew point temperatures in the low to mid 70s. At the same time, a jet speed maximum was moving across the northern tier of states. Speeds were around 75 knots at the 500 mb level with speeds in excess of 125 knots at the 250 mb level. This, in combination with a weak surface cold front, set the stage for the development of a mesoscale convective system over eastern South Dakota. The storms formed during the early morning hours and hit Iowa shortly after dawn. They moved east-southeast across the north third of the state. The system eventually took on the characteristics of and became a derecho as it raced across the state. By sunset, the centroid that moved across Iowa had reached southeast Ohio. The main severe weather features with the storms was hail and high wind. One inch to golf ball size hail pelted an area from Kossuth, through Wright, Franklin, to Butler County. Extensive crop damage was reported, though fortunately some of the crops had already come close to maturity. There was a swath of very large hail that fall across Palo Alto and Wright Counties. Baseball size hail pelted the area from northwest of West Bend to north of Clarion. Windows were broken out of houses between Rodman and West Bend in Palo Alto County. Crop damage was extensive as well. Winds from the storms were generally in the 40 to 50 MPH range, however several reports of 60 MPH winds, along with tree and power line damage, were received.