It’s pouring rain. It’s dime hail. It’s…a massive insect invasion in Pennsylvania?
No, we are not talking about mosquitoes, which are so big that they risk being mistaken for airplanes on radar. But newer technology is allowing meteorologists to pinpoint non-weather scatter on their data displays, and it’s the time of year when things are a lot more noticeable.
Sensitive radar recently took advantage of the cloudless Pennsylvania sunsets to capture a vast expanse of bugs, bats and birds ? collectively called biota. A recent incident was noted in a tweet by the National Weather Service at State College on April 6th.
“Even when there are no clouds or precipitation, our radar can still scan objects in the atmosphere,” the tweet said.
Meteorologist Ed Vallee, who provides forecasts for The Morning Call, said the swarms are visible thanks to dual-polarized (or dual-pole) radar, which picks up anything that gets in its way — a bug, a raindrop or a cloud Snowflake – and determines exactly what object it is.
“It’s kind of a perfect storm where you have clear skies, no precipitation, and you have that time of year, and you factor in all of those things,” Vallee said.
But just as it’s difficult to predict a perfect storm, it’s also difficult to predict the biological characteristics of a perfect swarm. In most cases, the bugs literally fly under the radar. But on July 22, 2015, the Weather Service forecast office in Norman, Oklahoma captured what appeared to be rain clouds over western North Texas. The “clouds” turned out to be bugs, including locusts and beetles, flying between the ground and 2,500 feet, covering about 50 miles.
That same week, thousands of mayflies landed on the Savanna-Sabula Bridge near Sabula, Iowa. There were so many that a snow plow was used to clear the street.
Closer to home, a flock of muckleheads — insects that hatch from Lake Erie in late spring — were spotted on radar last June as they descended into northeast Ohio.
If the thought is enough to make you run for the next can of bug spray, fear not.
It’s unlikely the Lehigh Valley would see such a massive swarm of insects, but that doesn’t mean we wouldn’t see a cloud of insects on radar in that area, said Marten Edwards, a professor of biology at Muhlenberg College in Allentown.
“I wouldn’t be at all surprised if a similar phenomenon were visible on a sufficiently sensitive radar system here in the Lehigh Valley,” Edwards said. “Insects often become active around sunset or sunrise, and when they migrate, they often migrate at night.”
Edwards said it’s a sense of self-preservation that leads to the timing of beetle blooms – appearing at the same time offers a degree of certainty in numbers. He likened the beetles to a school of fish, making it harder for predators to pick just one from a large group than to snatch up a single straggler.
“For many flying insects, sunset is the sweet spot between the risk of being eaten by birds, which generally need the light to hunt, and being eaten by bats, which use echolocation to hunt in the dark,” Edwards said.
While the sheer numbers of flying insects are impressive on radar, they are often significantly higher in agricultural areas and are typically active, not passive, migrants. This means that depending on the season, they choose to ride the wind.
“We’ve warmed up quite significantly, which obviously has accommodated the increase in bugs,” Vallee said. “We’re just starting to get around the corner with temperatures, so I think it’s a combination of the favorable weather, which is typical, and also the radar that makes it a pretty unique picture.”
Those who like to keep track of the biota can do so from their phones using apps like RadarScope. For weather enthusiasts and the general curious, it’s a way to scratch the itch without getting close to the swarm.