Not a cloud in the sky … or is there? Amid warnings that the monarch butterfly is endangered comes this heartening mystery from a weather room in St. Louis. Migrating monarchs caused the radar to do strange things, prompting confusion among meteorologists.
“It was a completely clear day — there were not even high clouds — and so we were all kind of scratching our heads saying ‘what are we looking at here?’” said Laura Kanofsky, a meteorologist for the National Weather Service in St. Louis. “It was not ground clutter, or mid-level clouds, which we can sometimes get in Friday’s conditions.”
While forecasters aren’t totally sure what it was, it’s likely the radar caught the butterflies mid-flight on their way south to Mexico where the species spends the winter. “A Monarch in flight would look oblate to the radar, and flapping wings would account for the changing shape!” wrote the forecast office.
From the radar echoes, it might seem as if there was quite a swarm of butterflies heading south on Friday. However, it doesn’t take much for the radar to light up when it’s dry out. “In dry conditions, the radar is very sensitive to something like insects,” said Kanofsky. “It doesn’t take a whole lot of insects to create a high return.”