COLUMBUS, Ohio (WCMH) — A few bands of showers and gusty thunderstorms rolled across the Columbus area early late Saturday afternoon and early evening, bringing much-needed rain after two weeks of dry weather.
However, the second line that formed a little after 6 p.m. caused pockets of straight-line wind damage in Upper Arlington and Hilliard associated with a “wet microburst.”
As is often the case in a dry spell worsened by summer heat, the sporadic rain comes with some extra wind.
There was enough humidity to foment scattered storms ahead of a “backdoor cold front” dropping southwest across central Ohio, which is the opposite of a typical west-to-east frontal passage. The weird pattern is due to the alignment of the winds aloft flowing counterclockwise around low pressure over New England.
What caused this narrow band of storms to intensify was a combination of city heat rising upwards, lifted by the cold front, and dry air aloft beneath upper-level high pressure. The storm ingested that dry air, which caused raindrops to evaporate.
Evaporative cooling makes the column of air much heavier than the surrounding storm environment, creating powerful downdrafts that hit the ground with considerable force, often snapping branches and felling trees that can become entangled with power lines in wooded areas.
When a large pulse-type storms moving rapidly collapses, usually within an hour after forming, the rain-cooled outflow acts as an exhaust mechanism, which produces a concentrated surge of wind capable of reaching speeds of 50-80 mph in a localized area.
The unusual trajectory of storms Saturday, arriving from the northeast and moving across the Scioto River Saturday, may have played a role in the more intense bursts of wind that were funneled through the smoother corridor of the river valley.
A narrow swath of pea-sized hail preceded the strongest winds as the line moved west across Upper Arlington before the wind arrived, signaling a strong updraft.
Multiple microburst events occur every year in Ohio, causing damage that spreads out laterally, rather than a rotary pattern associated with a spin-up tornado. Downbursts are most likely to occur in a humid environment near the surface, with taller storms that tap into stronger winds aloft.