Meteorologists at the National Weather Service office in Duluth noticed unusual blip on their radar screen Thursday afternoon - a plume of clouds, or smoke, emanating from the Sax-Zim Bog southeast of Hibbing on an otherwise cloudless afternoon.
The plume looked much like the start of a wildfire, with a pinpoint source then fanning out in the breeze. So the Weather Service called 911, which in turn dispatched firefighters, who investigated but found no fire in the area.
The plume continued for several hours, moving southeast on the northwest wind. Then it was gone.
The experts at the Weather Service hadn't seen anything quite like it before. When they postulated on Facebook, they got several suggestions, including aliens. Some suggested it was the steam plume from the United Taconite processing plant in Forbes, but the GPS coordinates didn't match. Besides, that plume is nearly constant and hadn't shown up before.
So the Weather Service came up with their official answer.
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"We figured it must have been some large amount of bugs," said Carol Christenson, National Weather Service warning coordination meteorologist. "What kind, we don't know."
The plume never showed up on satellite photos, also contributing to the theory that the source was biological and not meteorological.
Christenson said it's not uncommon for Doppler radar to pick up large flights of migrating birds or even swarms of mayflies rising out of a river.
"Usually you see bugs early in the morning, or birds, because that's the time when the radar beam is undergoing ducting; it's being bent toward the earth more" by atmospheric conditions so it picks up things closer to the ground, she said.
But this happened in the afternoon. The swarm was moving southeast, toward Duluth, but there have been no reports anyone seeing an unusual amount of insects.
"We're still going with bugs, though," Christenson said. "Because we can't think of anything else."
