Fifth Tornado from Monday Confirmed - Orland Park
A storm damage survey was conducted by NWS meteorologists in Orland Park on Wednesday evening. It was determined that a very brief EF0 tornado touched down and was immediately followed by a larger splat of microburst straight line winds. The storm circulation that caused this damage (referred to by meteorologists as a mesovortex) was the same storm circulation responsible for tornadoes in Griffith, IN as well as Bolingbrook, IL.
The tornado initiated in Orland Park along the south side of 135th Street one block east of La Grange Road. It tracked southeast through the neighborhood along Howe Drive snapping off numerous tree tops, downing three or four large trees, blowing down a fence, sending a gazebo swirling 30 feet into the air before depositing it in a neighbor’s yard, and damaging a roof on an auto shop along Southwest Highway. At this point the weakening tornado was wiped out by a microburst as it crossed the railroad tracks just east of Southwest Highway about a quarter mile south of 135th Street. The entire path of the tornado was ¼ mile long and 30 yards wide. The microburst that followed widened the damage path to a quarter mile wide and was about a third of a mile long. The microburst downed numerous trees in the area of Carolina Lane, 92nd Ave., Elm Street, and 137th and 138th Streets. Trees fell on rooftops, shingles were blown off a shed, there was damage to eves on homes, and there was porch and eve damage due to falling trees and branches. Power lines were downed due to falling tree branches.
Additional but more sporadic primarily tree damage extended along the same line to the southeast crossing 140th Street near Clearview Drive and along 144th Street between 87th and 84th Avenues.
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The type of damage observed in Orland Park was first classified by Dr. Ted Fujita (same researcher who invented the F scale for tornado classification – now used as the EF [Enhanced Fujita] scale) as a wide-end tornado while he worked at the University of Chicago during the 1970s. A wide end tornado by definition includes both tornado and downburst. It is believed that a strong downburst behind the weakening tornado undercuts the tornado circulation, in effect wiping out the swirling motion. This scenario is consistent with what eyewitnesses in the area observed on the evening of the 4th.
Tornado rated EF0 (Time - 800 PM CDT) with a path 0.25 miles long and 30 yards wide.