Damaging Winds in Wisconsin, October 4, 2002

During the mid-morning hours of October 4, 2002, a line of convective showers, orientated north to south moved east through south-central and southeast Wisconsin, and produced strong, gusty west winds generally in the 35 to 48 kt (40 to 55 mph) range with scattered reports of 52 to 61 kts (60 to 70 mph), an isolated "gustnado", and heavy rains. There were several reports of uprooted trees, etc. Interestingly, no thunder or lightning was reported by spotters or the general public, nor did any cloud-to-ground lightning strikes register on the national lightning detection network. However, off-duty National Weather Service (NWS) employees in Oconomowoc (Waukesha Co.) observed some cloud-to-cloud lightning. The line of convective showers was moving through an atmosphere that already had winds of 35 to 61 kts (40 to 70 mph) between 2 and 10 thousand feet above the ground. Mixing of air inside and near the downdraft/rain showers allowed for the transfer of these stronger winds down to the surface.As the line of showers moved through the remainder of southeast Wisconsin, it briefly intensified in scattered locations such that winds gusts over 48 kts (55 mph) were noted. A wind gust of 56 kts (65 mph) occurred at an Oconomowoc about 0900CST, a wind gust of 54 kts (62 mph) was measured in Germantown (Washington Co.) by a storm spotter about 0925CST, a 74 mph gust from the west-southwest was measured at the home of an Amateur Radio operator about 1 mile south of Hartland (Waukesha Co.) at about 0920CST, and a 58 kt (67 mph) gust was reported from a Sheboygan (Sheboygan Co.) school/TV network site. The 74 mph wind gust was associated with a "gustnado" that tore the roof off a home just two doors away on Manchester Lane. Across the street an apartment building sustained roof damage, and two support columns for the front door overhang were toppled. A sliding glass door on the 2nd floor of the apartment building was sucked out of the wall. In addition, a large 60-foot tree on an adjacent street was pushed over onto the roof a home, resulting in damage. Several other large trees were uprooted, and roof shingles were lifted off on a couple homes. Another apartment building sustained damage to a wooden deck. Just west of Hartland, the high winds knocked over a flat-bed farm trailer. On the west side of Eagle Springs Lake (Waukesha Co.) the powerful winds uprooted large trees, which damaged the roof of one residence, damaged a boat house, and two boats on trailers. In addition, the winds destroyed another boat house.Elsewhere in southeast Wisconsin, the Oconomowoc area had uprooted trees and toppled power lines, with one home sustaining damage due to a toppled tree. In Racine County the powerful winds uprooted trees and knocked tree branches loose which hit some power lines. Small tree branches were also knocked loose in all of the other southeastern Wisconsin counties. At least 8000 customers in southeast Wisconsin lost electrical power. Total rainfall associated with the showers ranged from 0.50 to 1.00 inches. Monetary damage amounts listed above are rough estimates.