Today marks the 9 year anniversary of the September 20, 2002 tornado outbreak. When we think about local tornado climatology, we don't tend to think of September as being an active month. The events of September 20, 2002 - and one tornado in particular - would turn climatology on its head.
The first of 6 tornadoes touched down in Posey county at 9:40 AM local time. It was on the ground for less than a quarter mile and caused no significant damage. The same thunderstorm would produce a stronger F2 tornado near Poseyville at 9:50 AM local time. This tornado destroyed 10 mobile homes and 4 other buildings and had a path length just under 5 miles.
After a break, another tornado would form in northwestern Pike county and move into Knox and Daviess counties. In Knox county, the tornado destroyed a few homes and damaged several others and peaked at F2 intensity. A conservation officer in his vehicle was thrown an eighth of a mile by the tornado. The tornado weakened to F0 as it moved into Daviess county, finally lifting after being on the ground for over 13 miles.
After another break in the action, the most notable tornado of the day touched down in Ellettsville at 12:59 PM local time and started producing F3 damage shortly thereafter. After weakening and heading northeast into Morgan county, the tornado reintensified and produced more F3 damage in Martinsville. The tornado remained at F2-F3 strength as it continued northeast into Johnson and Marion counties, producing additional F3 damage at Greenwood. The tornado took a slight left turn and entered the city of Indianapolis around 1:45 PM, generally producing F1-F2 damage on its trek through the southern and eastern portions of the city. The tornado exited Marion county just after 2 PM and continued northeast through several more counties, producing its final damage in Hartford City at 3:20 PM. In all, about 130 people were injured by this tornado with damage in excess of $150 million.
2 other tornadoes occurred simultaneous to the long track tornado. One of them damaged 10 single family homes and 30 mobile homes in Henry county and was rated F2. The other tornado destroyed 2 barns and 2 mobile homes in Rush county and was rated F0.
This event probably would've been forgettable were it not for the long-tracked F3 tornado. This tornado is interesting in several respects:
1) Its path length of 112 miles makes it one of the longest tracked tornadoes to ever hit the state (reanalysis of the April 3, 1974 Monticello tornado reduced the path length from 121 to 108 miles). The tornado was on the ground for a total of 2 hours and 21 minutes, giving it an average forward speed of about 48 miles per hour.
2) The tornado passed through 9 counties, second most behind the April 3, 1974 Monticello tornado
3) It is the second longest tornado to hit the United States in the month of September since 1950
4) The tornado did not occur as part of a discrete supercell; rather, it formed along a QLCS/squall line
5) Although the tornado was rain-wrapped much of the time and passed through urbanized areas, no deaths occurred
Here is a map of the tornado paths courtesy of NWS Indianapolis (note: Posey county tracks not included)
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