High Wind in Iowa, November 10, 1998

Iowa experienced the worst November storm system since the great storm of 9 and 10 November 1975. During the 9th, low pressure developed over southeast Colorado. The low moved across Kansas during the afternoon and evening of the 9th and deepened to about 990 mb. Warm and moist air was drawn north ahead of the low resulting in widespread across the state. Thunderstorms erupted during the late evening of the 9th, though no severe weather occurred. During the predawn hours of the 10th, a jet streak rotated around the base of the upper level low pressure area. The jet stream, combined with a tropospheric fold, resulted in explosive deepening of the low. As the low moved through Central Iowa pressures fell below 980 mb, with the low deepening to near 966 mb as it moved over northwest Iowa. The pressure at Spencer and Estherville dipped to 28.54 inches of mercury. This level represents an all-time low for the state of Iowa. At one point, based on CMAN data from several stations in Lake Superior, it appears the low deepened to about 940 mb for a period of 4 to 6 hours during the late afternoon and early evening of the 10th. As the low moved north, high winds swept across the state. Most of the state experienced a period of 12 to 18 hours of sustained winds of 35 to 50 MPH, with frequent gusts of 65 to 75 MPH. The highest official wind gust reported in the area came from La Crosse, WI, where the storm produced wind gusts of 93 MPH. There were unofficial reports of 78 MPH winds east of Tama. Officially, some of the higher winds include 68 MPH at Waterloo, 66 MPH at Mason City, and 67 MPH at Ottumwa. Almost every station in the state reported wind gusts above 60 MPH. Damage was widespread across the state with countless trees and power lines down. Over the northeast third of the state, spotty reports of gas line breakage were receive. Officials indicated the reason for this was that due to the prolonged period of high wind. The wind places stress on the buildings, and thus the pipelines, resulting in spotty failures. In addition to the tree and power line damage, several out buildings were downed by the high winds. There were also several reports of minor structural damage to buildings around the state, ranging from shingles removed to entire roofs. One school in Dallas County reported the roof of the auditorium was removed as the winds got under the roof lining and tore it off. The rocks from the gravel roof were then thrown through several windows in the school. A dormitory roof was damaged in Black Hawk County. Damage was estimated at between $70,000 and $90,000. Numerous reports of business windows being blown out were received from around the state. Semi-tractortrailer rigs were overturned along Iowas highways as the winds buffeted them. Over the northern third of the state, snow was also a problem as the high winds dropped visibility to near zero at times. The snow was not the main problem, however Interstate 35 was closed from Story City north to the Minnesota border due to high winds and blowing snow. There was one death during the wind storm in Hamilton County at Jewell. A man was repairing a roof and was blown off the roof during the storm. He was rushed to the hospital in critical condition, but did not survive. In addition, there were some livestock deaths as well. For example, near Mason City 60 head were lost as they moved into a culvert to get out of the wind and ended up freezing to death once they became wet.