Bloomington, IN Flood — Meteorology

A major flood event occurred in downtown Bloomington on June 18 and 19. Here’s an overview of just a couple pieces of the relevant meteorology.

Environment

A warm front lifted north through Indiana during the day, bringing dewpoints in excess of 70 F, and surface temperatures almost 10 F warmer than normal, even for June. The front would later stall and serve as the lifting mechanism for multiple rounds of storms.

Surface map from WPC, 19 UTC 18 June 2021

Deep atmospheric moisture, with precipitable water values that were 1-2 standard deviations above normal for June in Illinois and Indiana

The combination of extreme instability (see CAPE values in excess of 4000 J/kg, below) and a wind shear profile with only modest curvature (see the surface, 850 mb, and 500 mb wind “crossover” below) were favorable for multicell storms in the form of an MCS / squall line.

Radar loop to be inserted here later, but for now, here’s the 10 p.m. EDT radar image. These storms developed and moved almost parallel to Indiana Highway 46, between Terre Haute and Bloomington, for about three hours.

Precipitation Totals

From the CoCoRaHS network, consistent reports of 5 inches of rain, with one report in Ellettsville of 7.42 inches. At the Bloomington / Monroe County Airport, the report was 3.04 inches (I think), and the IU climate station reported 4.95 inches.

Climatology

https://twitter.com/indianaclimate/status/1406257208208375813

A smattering of damage photos in the next post.