Hail and Damaging Winds in Wisconsin, April 13, 2006

Wild weather occurred over parts of south-central and southeast Wisconsin on April 13, 2005. Wisconsin's most-costly hailstorm pummeled a large swath from around Mineral Point (Iowa Co.) to north of Milwaukee (Milwaukee Co.), while hurricane-force thunderstorm winds raked parts of Fond du Lac and Sheboygan Counties. Here's what happened: scattered supercells developed in eastern Iowa during the late afternoon hours of April 13th and pushed east-northeastward through southern Wisconsin and northern Illinois during the evening. Three main hailstorms affected southern Wisconsin. The first hailstorm left a swath of hail and hail damage from southern Iowa County (around 1945CST), through central Dane County, through northern Jefferson County, through northern Waukesha County, to northern Milwaukee County by 2151CST. This storm produced mainly 1 to 4 inch diameter hail, with a 4.25 inch hailstone reported by a State Trooper about 3 miles northwest of Lake Mills at 2055CST (larger hailstones of 4.5 to 5.7 inches in diameter have been reported in Wisconsin in previous years). A second hailstorm developed just south of the first storm and left a swath of hail and hail damage from northern Lafayette County (around 1956CST through northern Green County, through southeast Dane County., through central and southern Jefferson County, through central Waukesha County, to central Milwaukee County by 2210CST. This storm produced hailstones up to 1.5 inch in diameter. The third hailstorm developed in southern Dodge County around 2056CST, and pushed through southern Washington County into central Ozaukee County by 2139CST. This storm produced 1 to 2 inch diameter hail. Damage was widespread and extensive with the three hailstorms. Thousands of motor vehicles, residential homes, businesses, and farms sustained hail damage, but luckily, there were no reports of injuries or deaths. Vehicle damage consisted of broken windows and dented sheetmetal. Roofs, widows, and siding of buildings were damaged. Many water-birds were killed on several inland lakes. No crop losses were reported, given that the growing season had not started as of April 13th.Based on partial insurance company information and some estimation, the April 13th hailstorms resulted in total damage amounts of about $158.55 million. This makes the April 13th episode the most costly hailstorm to affect Wisconsin. Collectively in 9 counties, at least 23,500 vehicle claims, at least 18,650 residential claims, and at least 2,515 business/farm claims were filed with various insurance companies through June 30, 2006. These claims translated to at least $49.8 million in vehicle damage, at least $96.8 million in residential home damage, and at least $11.95 million in business/farm damage (new claims were still being filed as of June 28, 2006, therefore, these numbers may ultimately increase by 5 to 10%). Insurance company numbers, as provided to the Milwaukee/Sullivan WFO (monetary value of claims and number of claims), were not broken down by county. Therefore, estimated county-by-county breakdowns were derived - based on area affected in each county by hailstones 1.0 inches or larger, county population density, and relative sizes of the 20 largest insurance companies in Wisconsin. The estimated county monetary losses are: $66.59 million in Dane County, $22.2 million in both Iowa and Waukesha County, $17.44 million in Jefferson County, $7.93 million in both Milwaukee and Washington County, $6.34 million in Ozaukee County, $4.73 million in Lafayette County, and $3.17 million in Dodge County. These county numbers were then broken down and appropriated to the largest of the individual hail reports within each county (see header strips above).Last, but not least, a line of thunderstorms then pushed southeast out of Calumet and Manitowoc Counties through northeast Fond du Lac County and northern and eastern Sheboygan County between 2312CST and 2342CST. This line produced straight-line wind gusts up to an estimated 78 knots (90 mph) which caused extensive damage. Northeast Fond du Lac County was affected at 2315-2320CST, extending from 1.0 mile northwest of Marytown to 1.9 miles east southeast of Marytown. A dozen homes to sustain roof or siding damage, and on one farm a barn and a pole-shed were destroyed. Another farm had a barn and a garage destroyed and the nearby home was moved. Monetary damage amounts were estimated to be about $500,000 in Fond du Lac County. Sheboygan County was affected at 2325-2345CST, extending from Elkart Lake to 5 miles south of Sheboygan. In this area, 2 barns and 5 pole sheds were destroyed, trees and powerlines were pushed onto several cars, a roof was torn off of a home in the city of Plymouth, and a roof was torn off a garage in the Town of Plymouth. In addition, a cargo trailer in the city of Sheboygan was blown 60 to 70 feet and smashed into a building that housed several businesses. About 300 customers in the city of Plymouth were without power. The Sheboygan ASOS equipment at the Sheboygan airport northwest of the city of Sheboygan recorded a gust of 58 knots (67 mph). Monetary damage amounts were estimated to be about $400,000 in Sheboygan County. Synopically, a stationary front draped itself over southern Wisconsin during the afternoon and evening of April 13th. Temperatures climbed into the mid 70s across south-central and southeast Wisconsin during the afternoon. Moderate low-level instability, cold air aloft, and strong vertical wind-shear profiles with very steep lapse-rates caused storms to fire and produce giant hail.