Tornadoes and Flash Flooding in Wisconsin, July 2, 2000

Severe weather in the form of a tornado, damaging straight-line downburst winds, large hail, and flash flooding hammered a small piece of south-central and much of southeast Wisconsin during the late afternoon and evening hours. The most significant cluster of thunderstorms developed over southern Columbia county and proceded to move east/southeast through Dodge, Jefferson, Waukesha, Milwaukee, and Racine counties. A supercell on the west end of this cluster, with a well-defined mesocyclone, produced some damaging straight-line winds and large hail up to 2.25 inches in diameter in Jefferson County, but could only generate a rotating wall cloud at its base in that county. This supercell continued to dump large hail as it moved across Waukesha County, but once it moved over the city of Franklin in southwestern Milwaukee County, it spawned a tornado at 1730CST about 3/4 of a mile northwest of the intersection of Highways 41 and 100 (27th St. & Ryan Rd, or about 5.4 miles southwest of Milwaukee's General Mitchell International Airport). This tornado tore east/southeast through Oak Creek, and then exited Milwaukee County at 706 pm, where Highway 32 goes south into Racine County (or about 7 miles south/southeast of Mitchell Field). The tornado continued for about .2 miles into Racine County, just east of Highway 32, before dissipating about 2.9 miles northeast of Husher. Luckily, no one was injured or killed by the tornado that traveled through Franklin and Oak Creek into Racine County. It intensified to a F1 rating as it damaged buildings, and turned over several semi-tractor trailers at a truck stop at the intersection of I-94 and Ryan Rd. This tornado damaged at least a dozen homes in Franklin and Oak Creek, as well as one business and one utility building. Hundreds of trees were uprooted and blown over, but luckily many of them fell between buildings! Sixty power poles were snapped by the tornadic winds in Oak Creek. In Franklin, a 40-foot TV antenna was pushed over into a neighboring home, and a 20-foot camper was severely damaged. Eyewitness reports indicate that this tornado was rain-wrapped and was multi-vortex at times. Just south of the Ryan Rd. and 27th St intersection, a spotter indicated that sustained winds were greater than 40 mph for 15 minutes as the tornado passed just to the north of their position. In Racine County, the tornado uprooted trees as it weakened.The area from Johnson Creek to the Rome and Sullivan in Jefferson county sustained considerable hail and wind damage. Several vehicles on Interstate 94 near Johnson Creek, and in the Rome to Sullivan area, had windows broken by the large hailstones up to 2.25 inches in diameter. In addition, a few large trees were uprooted. Some of the corn crop in this swath had leaves stripped off. NWS employees at the NWS office southeast of Sullivan identified a rotating wall cloud about 3 or 4 miles west of their location.Waukesha County was raked by four rounds of severe storms. The 1st round possessed hurricane-force winds gusting to 68 knots (78 mph) at the Waukesha Airport near I-94. The city of Brookfield sustained tree and power line damage from this wet macroburst. The Jefferson County supercell constituted round #2 as it raked an area from Dousman to North Prairie (Waukesha Co.) with large hail and powerful downburst winds gusting to a measured 61 knots (70 mph). Hundreds of trees were uprooted and many power lines were downed. In North Prairie, 2 homes and a car sustained tree-inflicted damage. As this supercell moved east/southeast across Waukesha County, its strength pulsed upwards again and the Brookfield to New Berlin area experienced powerful downburst winds (round #3) that leveled more trees and power lines. A roof on an apartment complex in New Berlin was partially ripped off by the winds, but luckily no one was injured. Later in the evening, the 4th round of severe storms hit the Delafield to City of Waukesha area. Hail stones of almost an inch in diameter fell and powerful winds pushed over some trees.Racine County residents suffered the effect of 2 rounds of severe storms. Many trees and power-line poles were leveled in both rounds. At least 60 power-line poles were pushed over. At least 50 homes and 3 farm buildings in eastern Racine County were damaged by the powerful winds, or by felled trees. Scattered severe storms also produced large hail and/or damaging winds which leveled trees in Madison (Dane County), and southern Washington County (Richfield and Germantown).Collectively, about 70 thousand customers were without power at one time or another during the afternoon and evening hours on July 2nd due to downed power lines or lightning strikes to transformers. Twenty-five thousand of these were in Franklin and Oak Creek alone.Minor urban/small stream flooding affected parts of Waukesha and Racine Counties, as well as much of Milwaukee County after the 1st round of storms moved through and dumped rainfall of 1 to 2 inches. Water depths on roads were reported to be 6 to 12 inches. As with previous episodes of severe weather across southern Wisconsin during May and June, flash flooding occurred later in the evening on July 2nd, as additional rounds of storms, some severe, moved across the area. Torrential downpours, sometimes reaching an inch or more within 15 minutes, produced flash flooding across the southern half of Milwaukee County, the area from Hartland and Waukesha to Brookfield and Elm Grove in Waukesha County, and in/near the city of Racine (Racine Co.). Water depths on roads in these areas reached 1 to 4 feet. The flood waters resulted in gravel shoulder washouts on roads, structural damage to basements, damage to basement contents, and culvert damage. In the city of Franklin (Milwaukee Co.), a home's basement walls collapsed due to the pressure of the flood waters. Most small streams and creeks in Waukesha, southern Milwaukee, and eastern Racine County quickly exceeded flood stage by 1 to 2 feet due to the intense rainfall.The Root River in Franklin, the Root River Canal at Raymond (Racine Co.), Oak Creek in South Milwaukee, and the Menomonee River in Wauwatosa all crested between 2115CST on July 2nd and 0315CST the next morning. Homes and businesses near these locations sustained the worst flood damage. Collectively, the Milwaukee County flash flooding damaged 6974 residential homes, 38 businesses, 1 utility building, and 9 agricultural buildings. About 600 acres of farm land in southern Milwaukee County sustained crop damage. In Racine County, 429 residential buildings were damaged by flash flood waters, and about 2800 acres of farm land had crop damage or soil erosion.Urban/small stream flooding was reported in the city of Madison, in Sullivan, and around Richmond (Walworth Co.) due to the heavy rainfalls. Water depths on roads were in the 6 to 18 inch range. The Madison area picked up 1.5 to 2.5 inches of rainfall (Madison Truax Field had 1.89" for the day), the Sullivan area picked up an estimated 2.5 to 3.0 inches, and 3.7 inches fell in Richmond on the 2nd. No flood damage was reported from these locations.Two separate lightning strikes in Franklin started fires that damaged a car and a home's garage. Twenty-four hour rainfall amounts (mostly in the late afternoon and evening hours on July 2nd) ending 0600CST on July 3rd across southeast Wisconsin were impressive:Waukesha County...7.00" in Elm Grove, 5.06" at Carroll College, 4.27"in HartlandMilwaukee County...6.50" in Greenfield, 5.05" south side of Milwaukee, 4.75" in West Allis, 4 to 6" in Franklin, 4.22" at Milwaukee Mitchell International AirportRacine County...5.76" at Raymond, 3.99" in the city of RacineThe 4.42 inches of rain recorded at Milwaukee General Mitchell International Airport on July 2nd, set a new record for the day and a new daily record for any day in July. This was also the 6th wettest day for Milwaukee going back to the start of documentation in 1871. Milwaukee would finish the month of July 2000 with 7.12 inches of rain, the 3rd wettest July on record.Synoptically, an old frontal boundary sagged south across southern Wisconsin as low pressure moved east along it. A short-wave aloft was also moving east across the region. Moist, unstable air, drawn north into the frontal boundary, fueled the storms.