Mass Movements So Large You Can See Them on Radar

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Normally used to detect weather patterns, radars used by the National Weather Service have also been known to picked up other patterns.  The U.S. National Weather Service in Saint Louse, Missouri recently reported that a butterfly shaped pattern on its radar was the result of… butterflies.  The swarm of Monarch butterflies migrating was so large, it was  captured by weather radar.

The meteorologists determined that the patterns appearing on the radar were most likely biological and searched migration maps and consulted experts to see if they could figure out what was causing the pattern.  Bird migration was ruled out since the pattern didn’t match past experiences with bird flocks.  Since the timing was right the ultimate conclusion was that that this was the result of Monarch butterfly migration.

In a post on Facebook, the NWS reported:

Keen observers of our radar data probably noticed some fairly high returns moving south over southern Illinois and central Missouri. High differential reflectivity values as well as low correlation coefficient values indicate these are most likely biological targets. High differential reflectivity indicates these are oblate targets, and low correlation coefficient means the targets are changing shape. We think these targets are Monarch butterflies. 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!

Caused by Monarch butterflies in flight?

Caused by Monarch butterflies in flight?

Not all experts agree with the conclusion of the NWS in Saint Louis.  Some Monarch butterfly experts are skeptical, such as Wendy Caldwell who is the program coordinator for the Monarch Joint Venture at the University of Minnesota.  In an article posted by the St. Louis Post-Dispatch“If there are enough monarchs migrating through to cover a 200-mile stretch of land at one time, that would be a great thing,” Caldwell said. “But without more evidence, I would be hesitant to believe it. It could certainly be living things. There are many birds that migrate and dragonflies. It isn’t necessarily monarchs.”

While exactly what happened in the St. Louis area to cause the radar to explode in a blue pattern is still up for debate, there are other instances where mass movement by flying birds and insects have been captured by radar.

On September 14, 2014, the US National Weather Service Philadelphia/Mount Holly reported on its Facebook page that circular signatures captured by radar weren’t precipitation but from flocks of birds preparing for take off.

Yellow arrows indicate large flocks of birds taking off for the day.  Source: US National Weather Service Philadelphia/Mount Holly

Yellow arrows indicate large flocks of birds taking off for the day. Source: US National Weather Service Philadelphia/Mount Holly

The National Weather Service in Wilmington, Ohio has a collection of animations show the firework like explosion that mass bird movements make on its radars that occurred during the summer of 2010.

An eight-image animation of base reflectivity, starting at 6:12 AM and ending at  7:36 AM, August 2.

An eight-image animation of base reflectivity, starting at 6:12 AM and ending at
7:36 AM, August 2, 2010. Source: NWS Wilmington, OH Doppler radar imagery.

Bugs on Radar

The NWS in Flagstaff, Arizona tweeted out that bugs were so prevalent in the morning on April 20, 2013, they were captured on radar.

bugs-radar