EF3 tornado in Sullivan County, Indiana

This was the rotating supercell's first tornado, having traversed through Illinois for nearly 28 miles, producing EF3 damage before entering Indiana. The tornado crossed the Wabash River, entering Sullivan County 1.8 miles south of Merom. Near Merom, the tornado severely damaged 3 homes and destroyed a modular home which was thrown at least 200 yards to destruction. Two occupants of this home were killed. Also, a large trailer and several cars were thrown tens of yards from their resting location. The violent winds sheared off trees approximately 20 to 30 feet above ground.

The tornado continued across southern portions of the City of Sullivan. Dozens of homes and structures were severely damaged or destroyed, indicating the strongest winds of the tornado's entire 41-mile track that peaked near 165 mph. The tornado continued to locations immediately south-southeast, and then southeast of Sullivan, destroying at least 3 additional homes, including a modular home which was thrown at least 150 yards. One occupant of this home was killed, while the other was injured. Many trees were again sheared 20 to 30 feet off the ground. Continuing to the east-northeast, the circulation began to weaken as it continued into a wooded area, damaging numerous trees before lifting off the ground 3.3 miles east of Sullivan. Much damage in the area reached EF2-intensity (111-135 mph winds), with several locations where winds reached the EF3-intensity (136-165 mph winds).

A strong, occluding storm system over the Upper Midwest produced a deep column of strong southwesterly winds over the Midwest on the afternoon and evening of the 31st.

This pattern generated an inordinate amount of vertical wind shear. The overall southwesterly flow also brought rather mild and somewhat humid air into the region, which was adequately unstable given noticeably colder air aloft, especially over the southwestern quadrant of Indiana.

Resulting thunderstorms were able to mix down the stronger winds to the surface as damaging straight line gusts, while a rather low freezing level promoted isolated large hail. Ten tornadoes occurred across the region: 5 from a rotating supercell thunderstorm that tracked roughly parallel to and about 20 miles south of Interstate 70, and 5 others spawned from a squall line's northern book-end vortex that impacted north-central central Indiana. The supercell's first two tornadoes (both EF3) caused a combined 5 fatalities...before the supercell spawned two more strong tornadoes (EF2/EF3), with the cell's final EF3 inflicting major damage on a warehouse in Whiteland (Johnson Co.). The (northern) squall line's first tornado was an EF2 that impacted mostly rural areas...while the squall line's four following tornadoes were all weak (EF0/EF1), with the final three spawned over Howard County, concluding with a longer tracking EF1 that injured one person.