Tornadoes and Flooding in Iowa, May 19, 1998

A warm and humid air mass was located over Iowa during the afternoon of the 19th. Temperatures in this air were around 90 degrees F. Dew point temperatures were in the low to mid 70s, making for an unstable situation. A cold front was poised to the north of Iowa and was sagging southward slowly. Thunderstorms began to form over central Iowa during the mid afternoon hours. They formed rather quickly into a cluster of storms, with repeated development in the same areas. Most of the individual cells were right turning cells and many produced hail. Numerous reports of hail up to golf ball in size were received from in the Des Moines area, southeast toward Ottumwa. The cluster of storms that initially formed over central Iowa did eventually drift southeast toward the Ottumwa area just before sunset. The largest hail report came from Colo in Story County. Three inch diameter hail covered the ground to a depth of 4 inches between Colo and Collins. Needless to say, there were many reports of damage to roofs and cars. Fortunately, the largest hail remained just north and east of the densely populated Des Moines metro area. During the early stages of the storms development, a couple small tornadoes were reported. One was in Polk County, while the second was over Marian County. Both were small and only touched down briefly. The one over Marian County dipped up and down from the clouds several times during it's brief life span. No serious damage occurred as the tornadoes touched down in rural areas. In addition to the hail and tornadoes, the storms produced copious amounts of rainfall. Reports from the Ankeny area east toward Newton indicated very heavy rainfall from the storms. The southeast side of Ankeny reported 3.27 inches of rain in less than two hours time. This resulted in local flooding, however no widespread flooding occurred.