Tornadoes and Hail in Iowa, June 6, 1999

A cold front and dry line were approaching Iowa during the morning of the 6th. Overnight the preceding night, the dry line aloft moved into Iowa, however the dry line at the surface lagged behind by a few hundred miles. At sunrise, surface dew points were in the upper 60s to low 70s over western Iowa, while the dew point at 850 mb over Omaha had dropped to -8 degrees C. Little eastward progress occurred during the day as a strong upper level disturbance began to lift north from the Texas Panhandle. During the early afternoon skies cleared over western into central Iowa. Temperatures warmed into the upper 80s to low 90s, while at the same time temperatures in the mid levels cooled several degrees C. As a result, CAPE values were in excess of 4000 J/kg. By late afternoon, Iowa was in the rear entrance region of an upper level jet streak. Thunderstorms erupted as a result. Actually there were two short lines of convection. Both were oriented north-northeast to south-southwest and were moving northeast around 50 MPH. Severe weather developed rapidly and was mainly in the form of high winds and hail. There were several small tornadoes as well. Reports indicate that most of the tornadoes were brief spin-up tornadoes or gustnadoes. With the exception of two slightly stronger tornadoes, all of the tornadoes were very short lived F-0 tornadoes and produced little damage. A couple of the tornadoes did turn out to be a bit stronger. One in Webster County south of Otho was on the ground for a couple miles, while another was intermittently on the ground for over 10 miles in Franklin County. All of the tornadoes were over rural areas and consequently did little damage. Hail was very common with the storms as well. There were numerous reports of hail from three quarters inch up to golf ball size. One of the cells produced a two to three mile wide swath of one inch diameter hail across Kossuth County north of Algona, causing considerable crop damage. In addition to the hail, many locations reported winds of 60 to 70 MPH. High winds in Thornton lifted a steel grain bin and crushed it. In Hancock County, high winds from one of the storms blew a semi-tractortrailer over south of Corwith. The driver sustained minor injuries from broken glass. Winds were common since the storms were moving about 50 MPH themselves. Local law enforcement reported visibility reduced to under one half mile in blowing dust with several of the storms. Winds around 60 MPH swept through the Gowrie area in Webster County for example. Power was knocked out and many trees were toppled by the high winds. A barn was nearly destroyed near Stratford in Hamilton County.