Hail and Damaging Winds in Iowa, July 4, 1995

Moisture streamed north over the central United States during the 24 hours prior to this event. Surface dew point temperatures were in the 65°-70° F. range. A strong southerly low level jet had also become established during the day with speeds at the 850 mb level in the 50 kt range. On the surface, two fronts were approaching Iowa. One was a warm front to the south of the state. A cold front was moving in from the west. An upper level low pressure area was over north central Kansas during the early afternoon hours. The air mass was quite unstable with lifted indices in the -5° to -7° C. range. The air was even more unstable to the south of Iowa. Convective available potential energy (CAPE) values were around 2800 J-kg-1 with helicity values around 400 m2-s-2 by mid afternoon. Surface mesoscale analysis during the afternoon revealed strong moisture convergence into northwest Missouri and southwest Iowa. That is where the thunderstorms formed. During the mid to late afternoon, a line of thunderstorms formed rapidly from southwest into central Iowa. These storms produced a few funnel clouds, but there was not real threat of them touching down. During the early stages of development, lightning from one of the storms struck a house in Atlantic. No fire was started, however electrical damage was reported. The freezing level on this day was quite high, in excess of 13,500 feet MSL. As a result, hail was not a dominant feature with the storms. Spotty reports of hail between three-quarters on an inch and nearly an inch in diameter were received, but most of the hail was marble-size or smaller. Wind became the major problem with the storms. Within two hours of the initial onset of convection, the thunderstorm complex assumed a bow echo configuration. This bow echo tracked across the entire state producing high winds and brief torrential rains. In Taylor County of southwest Iowa. high winds in the Sharpsburg area downed trees onto a house. The trees crashed through the house and even resulted in some foundation damage. Damage to the house was estimated between $50 thousand and $60 thousand. Near Bedford, high winds downed a tree onto a house. One man was seriously injured as he was unable to get to shelter before the tree fell through the house. He was still in the hospital the following day. Damage to the house was between $8 thousand and $9 thousand. Other damage around the state was mainly tree and power line damage. There were spotty reports of roof damage, such as in the Prairie City area of Jasper County and the Brooklyn area of Poweshiek County. A tractor-semitrailer was overturned by the high winds on Interstate 80 near Newton. For the most part winds were around 60 mph with many of the storms. A few of the storms produced brief stronger gusts in what appeared to be microburst activity. Considerable damage was done in the What Cheer area in Keokuk County. There was some increase in the wind strength over the eastern counties of the state as the storm system began to die out. Winds from the decaying storms reached 60 to 70 mph in several areas of east central Iowa. One of the collapsing storms produced high winds west of Andrew in Jackson County. The winds picked up a 2 x 4 and threw it through the side of a pick-up truck. Flooding was not a large problem except during the early stages of the storm systems development. Heavy rainfall was reported in Taylor County. Two inches fell in 55 minutes time in New Market, while .90 inches fell in 15 minutes in Bedford. The rainfall only resulted in bank full stages on the smaller streams. Minor flooding, mostly in urban areas, was reported in Union County as the heavy rainfall moved through. It did not last long, nor did it cause much damage.