A tornado touched down in northeastern Kingsbury County South Dakota. The tornado was on the ground for at least 6 minutes. It hit a hog operation 4 miles north of Lake Preston, destroying a barn, two other outbuildings, and downing several trees. However, the farmhouse was undamaged by the tornado. No injuries were reported with the tornado as it moved along 204th St in Kingsbury County. However, numerous hogs were killed by the tornado. Below is a pictures of the thunderstorm which produce the tornado taken by Donna Budahl. Donna was located on Highway 81 nine miles north of Madison, South Dakota. While the picture does not show the tornado, one can see the cumulonimbus cloud with an overshooting top and anvil. The tornado would have been located on the left side of the picture (southwest side of the storm.
Below we also have an overview of the lowest elevation of the storm from reflectivity and the storm relative velocity. The storm relative velocity will show the rotation within the thunderstorm approximately 5000 feet above the ground. The storm began to develop around 5:49 pm. There was evidence of a thunderstorm developing northwest of De Smet. A weak circulation was associated with this updraft. There also is evidence of a dryline east of Madison, South Dakota. While the dryline was not evident farther north, it is hypothesized that the dryline was located just east of this developing cell.
At 6:14 pm, the storm had intensified and the circulation had begun to strengthen. The circulation remained much weaker than what is typically seen with tornadic thunderstorms. Typically, the rotation on radar associated with a tornadic thunderstorms is greater than 40 mph. However, in this case, the rotation was between 10 and 20 mph. However, the rotation was rather narrow - only 2 to 4 miles wide.
While the circulation was weaker than generally observed with tornadoes, the storm was in a location which was favorable for tornadoes. One parameter meteorologist examines is the low-level instability. To do this we examine a quantity called convective available potential energy (CAPE). Specifically, meteorologists examine the CAPE up to 3 km since if there is a lot of energy below 3 km then it is more likely a tornado will develop. The graphic below shows that the axis of the largest 3 km CAPE extended into eastern Kingsbury County.
Forecasters also examine the change in wind speed and direction in the lower atmosphere called shear. For tornadoes, it is usually necessary to have a lot of shear to increase the rotation within the thunderstorm. The image below shows that the shear below 1 km was 15 to 20 kts which is sufficient for tornado development.
In the next 5 minutes the storm continued to intensify and at 6:19 pm cdt, the radar showed a strong storm over northeast Kingsbury County with some rotation. This is when the tornado touched down north of Lake Preston.
At 6:23 pm, the tornado destroyed portions of a hog confinement 4 miles north of Lake Preston. Here is how it looked on radar.
The storm began to rapidly weaken after 6:23 pm. The next image is from 6:48 pm and notice that the circulation is no longer evident and the storm is no longer above 30 dBz on reflecitivity. Calls to weather spotters north of Arlington indicated that the rotation within the storm had disipated between 6:35 pm and 6:45 pm.