The 1996 Oakfield tornado outbreak was a severe weather event that occurred on July 18, 1996 in

Wisconsin Wisconsin () is a state in the upper Midwestern United States. Wisconsin is the 25th-largest state by total area and the 20th-most populous. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake M ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

, primarily affecting the village of Oakfield. The outbreak produced 12

tornado A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, altho ...

es, with the most significant being an F5 tornado which caused severe damage to the village and the surrounding areas. No deaths were associated with the outbreak, with 17 injuries in total. 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) in the tornado's core as it carved a path approximately 20 miles (32 km) long. Destruction in Oakfield included leveling homes, sending vehicles airborne, bending steel rebar, and sweeping crop fields clean. The Oakfield tornado remains one of the costliest tornadoes in the state's history, with the estimated damage costs at $40 million USD.

Meteorological synopsis

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 A weather front is a boundary separating air masses for which several characteristics differ, such as Density of air, air density, wind, temperature, and humidity. Disturbed and unstable weather due to these differences often arises along the b ...

. This boundary generated strong

cyclonic rotation Cyclonic rotation, or cyclonic circulation, is atmospheric motion in the same direction as a planet's rotation, as opposed to anticyclonic rotation. For Earth, the Coriolis effect causes cyclonic rotation to be in a counterclockwise direction in the ...

around a surface low-pressure center over

Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...

. Warm and moisture-laden air from the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...

flowed northward into the

Upper Midwest The Upper Midwest is a region in the northern portion of the U.S. Census Bureau's Midwestern United States. It is largely a sub-region of the Midwest. Although the exact boundaries are not uniformly agreed-upon, the region is defined as referring ...

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 South Dakota (; Sioux: , ) is a U.S. state in the North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota and Dakota Sioux Native American tribes, who comprise a large porti ...

and

Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the sout ...

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 Convective inhibition (CIN or CINH) is a numerical measure in meteorology that indicates the amount of energy that will prevent an air parcel from rising from the surface to the level of free convection. CIN is the amount of energy required to ov ...

(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. By 3:33 PM CST, the

National Weather Service The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...

in Milwaukee/Sullivan saw the potential for severe weather, including tornadoes, and issued the first

tornado watch A tornado watch ( SAME code: TOA) is a severe weather watch product issued by national weather forecasting agencies when meteorological conditions are favorable for the development of severe thunderstorms capable of producing tornadoes. In addit ...

which covered a majority of Wisconsin, followed by a second at 6:47 PM.

Confirmed tornadoes

July 18 event

Aftermath

Following the tornado outbreak, Wisconsin Governor

Tommy Thompson Tommy George Thompson (born November 19, 1941) is an American Republican politician who most recently served as interim president of the University of Wisconsin System from 2020 to 2022. A member of the Republican Party, he previously served a ...

declared a state of emergency for

Fond du Lac County Fond du Lac County is a county in the U.S. state of Wisconsin. As of the 2020 census, the population was 104,154. Its county seat is Fond du Lac. The county was created in the Wisconsin Territory in 1836 and later organized in 1844. Fond du La ...

, resulting in the deployment of the

National Guard National Guard is the name used by a wide variety of current and historical uniformed organizations in different countries. The original National Guard was formed during the French Revolution around a cadre of defectors from the French Guards. Nat ...

to aid victims and clear debris. In total, 47 of 320 homes were destroyed and 56 homes were heavily damaged, along with numerous businesses and churches. Damage estimates reached over $40.4 million USD, marking the outbreak the costliest in state history. 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. The 25th anniversary of the tornado was observed on July 18, 2021, 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.

Notes

References

External links

Oakfield Tornado write-up
from the

Photographs of tornado from storm chaserMap of July 18, 1996 tornadoes
{{DEFAULTSORT:1996-07 Oakfield Tornado F5 tornadoes Tornadoes of 1996 Tornadoes in Wisconsin Oakfield Tornado 1996 Oakfield tornado Tornado 1996-07 Tornado 1996-07