Meteorological synopsis
Conditions over South Dakota were favorable for supercell development on May 22, [a 1] caused by a low-level jet stream that had advanced over the Midwest and plains region. [a 2] CAPE values in the area were as high as 4,840 joules per kilogram. [a 2] A weak surface low formed in the afternoon hours,encompassing portions of South Dakota,including the area where the Bowdle tornado would occur. [a 2] The supercell that produced the tornado first formed at 22:00 UTC,one of several cells that fired over a north-south stretch near the Missouri River. [a 2] The supercell cycled at least five times,the fifth producing two tornadoes. The first tornado was confirmed by storm chasers and received an EF1 rating,being on the ground for six minutes. [a 3] The supercell gained a defined hook echo around this time,producing a rotating wall cloud that was visible on the ground. [a 3] The cell also garnered a large rain curtain just prior to dropping the Bowdle tornado. [a 4] Circulation that had produced the first tornado merged with a broader area of rotation,strengthening before producing the Bowdle tornado. [a 5]
Tornado summary
The tornado first touched down by a farmstead in eastern Walworth County,approximately 6.8 miles (10.9 km) away from Bowdle. [a 5] At the time of the tornado touching down,the parent supercell was in the process of cycling. [a 6] A 2010 study produced by numerous scientists,including tornado researcher Tim Samaras,determined that the tornado was likely a smaller condensation funnel within a larger area of circulation,but began to rapidly intensify and became the dominant funnel as it crossed South Dakota Highway 79. [a 6] The visible funnel of the tornado centered itself in proportion to the supercell's mesocyclone as it moved to the northeast;a multiple-vortex structure was documented within the tornado. [a 6]
Immediately at EF2 intensity,several outbuildings were severely damaged with the residence sustaining siding and roof damage. A stock trailer was thrown about 75 yd (69 m) from its original location. Tree damage was sustained on the west side of the property. The tornado continued moving northeast crossing into Edmunds County,where it then briefly weakened to EF1 strength,where it snapped and broke power poles. [a 6] At the first farm,several large cottonwood trees were uprooted along with damage to several trailers. Three grain bins were also destroyed. The residence suffered some shingle and antenna damage. [1] [4] The tornado then abruptly weakened over a span of thirty seconds,losing a visible condensation funnel. At this point,the tornado was estimated to have been 220 yards (200 m) in width. [a 7]
The tornado rapidly intensified as it moved to the northeast, [a 8] [5] quickly intensifying to EF3 strength where it impacted a second farm 1.5 mi (2.4 km) northwest of Bowdle. At this farmstead,several outbuildings were damaged or destroyed along with widespread tree damage. The main residence at this location suffered no damage. Several grain cars were also rolled about 100 yd (91 m) into the trees behind the house. As the tornado exited this farmstead,it intensified to EF4 strength before tearing through a third farmstead. At this farm,the main residence suffered major damage to walls with part of the roof removed. [1] [4]
Widespread tree damage was sustained with many of the trees completely debarked with only the stumps of the largest branches remaining. Two large garages were completely destroyed with the concrete slab wiped clean. The vehicles in one garage were rolled or tossed from 25 yd (23 m) to 100 yd (91 m) yards away. Another vehicle flew through the air before resting in a tree shelter belt to the north of the residence. Several other outbuildings were completely destroyed.The tornado then toppled six to eight metal power transmission towers as it moved to the north of the farm. One tower was sheared off from the concrete footings and was thrown an estimated 400 yd (370 m). Ground scouring was visible along the path of these towers. The large tornado began to track east,declining to EF2 intensity before crossing over SD-47 where a state radio tower was toppled. The tornado lifted a short time later. [1] [4]
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