at 10:10 AM by Pierce Larkin

Tornado Impacts Western Part of Indianapolis, IN

Last evening, a small and unique supercell formed in central Indiana, just west of Indianapolis. This supercell formed in a fairly favorable environment for a supercell to develop and be sustained in. While upper level flow was generally fairly weak across the region, the wind shear in the lowest portions of the atmosphere was primed for tornadoes. With upwards of 300 m2/s2 of 0-3km Storm Relative Helicity (measures the tendency of an updraft to rotate), and 25 to 30 knots of total shear in the lowest 1 km of the atmosphere, the wind shear was absolutely in place.

The bulk shear in the lowest 1 km of the atmosphere. h/t SPC
The bulk shear in the lowest 1 km of the atmosphere. h/t SPC
0-1km SRH was very high, and primed for updraft rotation. h/t SPC
0-1km SRH was very high, and primed for updraft rotation. h/t SPC
0-3km SRH was very high, and primed for updraft rotation. h/t SPC
0-3km SRH was very high, and primed for updraft rotation. h/t SPC

Additionally, the surface conditions were primed for this as well. The supercell formed on a northeasterly propagating warm frontal boundary, and warm fronts are traditionally a source of enhanced wind shear as the surface flow backs from southerly flow south of the warm front to a more easterly flow north of the warm front.

The surface low, cold front and warm front positioning last evening. Indianapolis is very close to the warm front. h/t SPC
The surface low, cold front and warm front positioning last evening. Indianapolis is very close to the warm front. h/t SPC

Moisture was plentiful across the region, with dewpoints in the 70s across the region. This allowed for LCLs (Lifted Condensation Levels) to be below 750m, which is primed for tornadogenesis.

LCLs have been shown to be a big part of tornadogenesis, and the LCLs were below 1000m. h/t SPC
LCLs have been shown to be a big part of tornadogenesis, and the LCLs were below 1000m. h/t SPC

 

All of this came together to produce a strong supercell, that produced a strong, long tracked tornado across the western suburbs of Indianapolis.

That is unique. 

The National Weather Service in Indianapolis is out surveying the damage, and they should have a rating up later. Luckily, there were no reported injuries or fatalities, which is good considering the size of Indianapolis.