Strange storms in Tallahassee: The science behind them

Thursday’s severe thunderstorms were really impressive, even for us meteorologists.

It certainly wasn’t the usual summer storms we frequently encounter. I (Henry) first heard thunder around 4:30 PM when I was still at Florida State University.

I left for home and tried to weather the storm, but had no luck. On the way I saw for the first time a lot of evil lightning from the cloud to the ground. While driving further, it started to rain, as heavy as I had ever seen.

Parts of Gadsden Street began flooding. I can barely see the cars in front of me. However, when I got home (five miles northeast of campus), it was all over, and the rainfall was less than a tenth of an inch. Some sites received much more.

However, there was more to this storm. A small, wet explosion occurred and was clearly observed on the National Weather Service’s Doppler radar. A microburst is not the same as a tornado. They are very strong downdrafts that move toward the ground as the wind spreads horizontally in all directions. They are small, usually less than 2.5 miles in diameter, and have wind speeds of more than 150 miles per hour. Fortunately, our strength was not that strong.

Weather radars do not detect winds in all directions, but only in the direction (colored in green) or away from the radar beam (colored in red). A screenshot of the Tallahassee radar image at 5:23 PM clearly shows this classic signature. This zoomed-in view shows the small explosion centered northeast of the airport’s radar (black circle).

The second round started around 7:30 p.m. We all saw the ominous clouds in the north moving towards us; So Kerry (my brave weather dog) and I sat on the front porch and waited for him to arrive.

It happened quickly, and the strongest wind speeds were probably around 60 mph, as strong as those coming from Idalia, but not as long-lasting as those coming from Idalia. The neighbors’ pine trees were really swaying, and one of them cracked about 20 feet above the ground, barely missing their house.

Since we were getting wet from the heavy rain, Kerry and I gave up and went inside. Our electricity went out immediately and remained out until 10pm. Some of my colleagues didn’t get power until 1:30 a.m., and you were probably in the same boat – maybe longer.

Doppler radar showed that these winds were not caused by a small explosion like the previous storm but were strong “straight line winds” that increased the damage in the afternoon.

It was literally raining cats, dogs, and squirrels (I saw three dead squirrels in the street the next morning on Kerry’s walk). Although my wonderful rain gauge showed a peak rain rate of 8.5 inches per hour (also very impressive), this significant rain rate was short-lived. I ended up with exactly 1 inch of rain. Sometimes small hailstones interspersed the rain.

In terms of lightning, there was a lot of it. Looking at all of Leon County, there were 501 cloud-to-ground (CG) strikes plus an additional 2,448 in-cloud flashes – a total of 2,949. The strongest current was 86,000 amps, compared to my home’s circuit breaker’s 50 amps.

If you watch it carefully, it appears to be blinking. For most lightning researchers, 15 is a very high number.

Although Thursday’s storms were impressive, I don’t want another one any time soon, and you probably don’t either.

Henry Feulberg is a professor of meteorology at Florida State University. Jagdish Desai is a second-year meteorologist majoring and conducting a research project on lightning in our area.

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