Weather Radar Picks Up Strange Image (Its Shape Could Be a Clue to What Caused It)

Late last week those keeping tabs on the St. Louis National Weather Service radar might have seen an odd formation that actually had nothing to do with the weather.

Image source: NWS St. Louis/Facebook

"High differential reflectivity values as well as low correlation coefficient values indicate these are most likely biological targets," a Facebook post from NWS said. 

Basically, the weather service is saying that the image was likely triggered by something that's alive. But what?

"We think these targets are monarch butterflies," NWS wrote. "A monarch in flight would look oblate to the radar, and flapping wings would account for the changing shape! NWS St. Louis wishes good luck and a safe journey to these amazing little creatures on their long journey south!"

Image source: NWS St. Louis/Facebook

As a commenter on one of the images put it, the shape that appeared on the radar was "kind of the shape of a butterfly too."

According to a sightings map from Learner Journey North, an organization that produces teaching materials, monarch butterflies very well could have been passing through the area on their migration down to Mexico on Sept. 19 when the strange cloud was spotted by radar.

In a comment, NWS clarified that it wouldn't even take a large swarm of butterflies to create the radar image.

"So it could have just been the beginnings of the migration through the region," NWS wrote. "There was a good north wind at the levels we saw the returns at. So according to the Sophia M. Sachs Butterfly House, butterflies love to take advantage of a tail wind!"

This is not the first time a "biological target" has come up on weather radar. Earlier this year a "roost ring" made by birds appeared in the shape of a donut on radar.

(H/T: CityLab)