| Duration: | 3 hours, 8 minutes[1] |
| Basin: | atl |
| Tornadoes: | 12[2] |
| Fujita-Scale: | F5 |
| Winds: | 230 |
| Season: | tornado outbreaks of 1996 |
The 1996 Oakfield tornado outbreak was a severe weather event that occurred on July 18, 1996, in Wisconsin, United States, primarily affecting the village of Oakfield.[3] The outbreak produced 12 tornadoes,[2] with the most significant being an F5 tornado which caused severe damage to the village and the surrounding areas. As of the present, this remains the most recent EF/F5 tornado to have occurred in the United States outside the peak months of April and May. No deaths were associated with the outbreak, with 17 injuries in total.[3]
The most intense tornado of the outbreak initially touched down at 6:05p.m. CST (00:05UTC) 4 miles northwest of Oakfield, before rapidly intensifying to F5 strength just east of the village. Estimated wind speeds reached 265 mph (426 km/h)[5] in the tornado's core as it carved a path approximately 20 miles (32 km) long.[3] Destruction in Oakfield included leveling homes, sending vehicles airborne, bending steel rebar, and sweeping crop fields clean.[6] The Oakfield tornado remains one of the costliest tornadoes in the state's history, with the estimated damage costs at US$40 million.[4]
On July 18, 1996, the meteorological conditions leading to the Oakfield tornado outbreak were influenced by the presence of a nearby shifting weather boundary, known as a baroclinic zone. This boundary generated strong cyclonic rotation around a surface low-pressure center over Minnesota.[7] [2] Warm and moisture-laden air from the Gulf of Mexico flowed northward into the Upper Midwest due to a dominant southerly wind pattern. Strong fronts displayed frontogenetic behavior, with frontogenesis at 850 hPa level curving from the border of South Dakota and Nebraska to Wisconsin, leading to strong ascent in the warm sector of the surface low-pressure system.
Despite these conditions, no severe storms occurred in the morning hours. This was because of a high convective inhibition (CIN) value caused by the presence of an elevated mixed layer (EML) and a 550 hPa inversion, which made it difficult for convection to break through. Additionally, the effects of daytime heating had not yet weakened the inversion. As the day progressed, daytime heating and evolving atmospheric conditions allowed the cap to be broken and provided the necessary ingredients for the development of the severe weather outbreak, including the devastating F5 Oakfield tornado.[2]
By 3:33 PM CST, the National Weather Service in Milwaukee/Sullivan saw the potential for severe weather, including tornadoes, and issued the first tornado watch which covered a majority of Wisconsin, followed by a second at 6:47 PM.[5]
| Location | County / Parish | State | Start Coord. | Start Time (UTC) | Path length | Max width | Summary | |||
|---|---|---|---|---|---|---|---|---|---|---|
| bgcolor=# | F1 | SW of Tomahawk to W of Gilbert | Lincoln | WI | 22:20 | 3miles | 100yd | Three cottages, one home and a tavern were damaged. A garage was removed from its foundation and two boats were flipped.[8] | ||
| bgcolor=# | F1 | NE of Princeton | Green Lake | WI | 23:15 | 2miles | 125yd | Damage was limited to trees.[9] | ||
| bgcolor=# | F2 | S of Jericho to Marytown | Calumet, Fond du Lac | WI | 00:05 | 6.4miles | 200yd | North of Marytown a couple dozen barns, sheds and homes were damaged or destroyed. In Marytown a house trailer, three homes and a machine shed were destroyed. In rural Calumet County two barns, trees, crops were damaged and calf houses were thrown 1000feet. One person was injured.[10] | ||
| bgcolor=# | F5 | Oakfield to N of Marblehead | Fond du Lac | WI | 00:05 | 13.3miles | 400yd | Four homes were swept from their foundations, and automobiles were carried 400feet through the air and mangled beyond recognition. Some of the homes were anchor-bolted to their foundations, and rebar supports along the perimeter of one home were bent over at a 90-degree angle. The Friday Canning Company was also leveled, sweeping up millions of empty cans and leaving them scattered over a 50miles radius. Out of the 327 homes in Oakfield, 47 were destroyed, and an additional 56 homes, as well as numerous businesses and churches, suffered heavy damage. 500acres of crops were also wiped away with only 1-inch stubble left. Damage totals reached $39.5 million (1996 USD) and 12 people were injured. The original National Weather Service report from Milwaukee/Sullivan categorized the tornado to be an F3 to F4 tornado on the Fujita scale. It was later upgraded to an F5, the most intense category tornado possible and the only F5 tornado to hit the United States that year. Collectively, a total of 60 homes, six businesses, a canning company, two churches, 18 barns, and several sheds were destroyed while 150 homes and businesses were also damaged.[11] The tornado was also documented by at least three experienced storm chasers.[12] A weaker tornado also hit the area 20 minutes later. | ||
| bgcolor=# | F0 | Marytown | Fond du Lac | WI | 00:07 | 1.2miles | 75yd | A second tornado struck Marytown, damaging farm crops.[13] | ||
| bgcolor=# | F0 | S of Charlesburg | Calumet | WI | 00:10 | 0.1miles | 25yd | Brief tornado flattened two wheat fields.[14] | ||
| bgcolor=# | F0 | Oakfield | Fond du Lac | WI | 00:25 | 0.6miles | 50yd | Second tornado moved through portions of the damage path of the F5 tornado, picking up debris from the ground but did not cause any additional structural damage.[15] | ||
| bgcolor=# | F0 | NW of North Fond du Lac | Fond du Lac | WI | 00:27 | 0.2miles | 50yd | A barn, machinery and crops were damaged or destroyed.[16] | ||
| bgcolor=# | F0 | NE of Lomira | Fond du Lac | WI | 00:55 | 0.1miles | 50yd | Brief tornado flattened portions of a corn field.[17] | ||
| bgcolor=# | F1 | S of Beechwood | Sheboygan | WI | 01:10 | 0.9miles | 150yd | Several homes and a few barns were damaged, along with crops.[18] | ||
| bgcolor=# | F1 | Fredonia to Holy Cross to ESE of Decker | Ozaukee | WI | 01:18 | 7.6miles | 125yd | Four barns, three machine sheds and a one-car garage were destroyed while six homes, a barn, three machine sheds and a garage were damaged. Several vehicles were also damaged or destroyed, as well as 500acres of crops.[19] | ||
| bgcolor=# | F0 | E of Knellsville | Ozaukee | WI | 01:28 | 0.8miles | 75yd | This tornado spent most of its lifetime over Lake Michigan, causing little to no damage.[20] |
Following the tornado outbreak, Wisconsin Governor Tommy Thompson declared a state of emergency for Fond du Lac County, resulting in the deployment of the National Guard to aid victims and clear debris.[3] [21] In total, 47 of 320 homes were destroyed and 56 homes were heavily damaged, along with numerous businesses and churches. Damage estimates reached over US$40.4 million, marking the outbreak the costliest in state history.[4]
Despite the severity of the F5 tornado and the extensive destruction it caused, no fatalities were reported, and a total of 17 people were injured during the outbreak. In the time that followed, the community of Oakfield received significant financial support from individuals and businesses in the form of donations and loans to aid in the rebuilding process. Much of the area's tree canopy and ecological landscape were devastated by the tornado, but through the concerted efforts of area residents and fundraising initiatives, over $102,000 was raised, and more than 1,400 trees were planted.[21]
The 25th anniversary of the tornado was observed on July 18, 2021,[5] with a series of commemorative events being held, including a parade, an outdoor church service, village-wide open houses, and a display of photographs and first-hand accounts of the tornado at the Oakfield Public Library's story walk in Acorn Park.[21]