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Bug Earth Communications United States Science

Massive 70-Mile-Wide Butterfly Swarm Shows Up On Denver Radar System (bbc.com) 47

dryriver shares a report from BBC: A colorful, shimmering spectacle detected by weather radar over the U.S. state of Colorado has been identified as swarms of migrating butterflies. Scientists at the National Weather Service (NWS) first mistook the orange radar blob for birds and had asked the public to help identifying the species. They later established that the 70-mile wide (110km) mass was a kaleidoscope of Painted Lady butterflies. Forecasters say it is uncommon for flying insects to be detected by radar. "We hadn't seen a signature like that in a while," said NWS meteorologist Paul Schlatter, who first spotted the radar blip. "We detect migrating birds all the time, but they were flying north to south," he told CBS News, explaining that this direction of travel would be unusual for migratory birds for the time of year. So he put the question to Twitter, asking for help determining the bird species. Almost every response he received was the same: "Butterflies." Namely the three-inch long Painted Lady butterfly, which has descended in clouds on the Denver area in recent weeks. The species, commonly mistaken for monarch butterflies, are found across the continental United States, and travel to northern Mexico and the U.S. southwest during colder months. They are known to follow wind patterns, and can glide hundreds of miles each day.
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Massive 70-Mile-Wide Butterfly Swarm Shows Up On Denver Radar System

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  • A few issues here (Score:5, Informative)

    by Anonymous Coward on Friday October 06, 2017 @08:53PM (#55325631)

    Why would it be unusual to see migratory birds going from north to south this time of year? That seems like what we'd expect from any migratory creature.

    Also, Paul Schlatter knows his stuff, so I don't think it's his error, but rather the reporter. It is very common for flying insects to be detected by radar, despite what the article says. More likely, it's rare to detect swarms of migratory insects. However, we see insects all the time on weather radar, usually seen as an area of relatively low reflectivity compared to storms (say, 10-20 dBZ, compared with 50 dBZ for storms) and it's seen close to the radar where the beam isn't too far above the ground. Sometimes the winds converge and cause the concentration of insects to increase in an area. When the winds converge, the air generally rises, but the insects resist ascending to a higher altitude. We see this a lot of times along fronts, drylines, outflow boundaries, and horizontal convective rolls. They usually appear as a line, usually a few kilometers wide, of stronger reflectivity (perhaps 20-25 dBZ), and it allows us to see where things like fronts and outflow boundaries are. We also use the motion of the insects with increasing height (as the beam gets farther from the radar) to estimate the wind speed and direction in the lowest kilometer or two of the atmosphere.

    When it's warm enough, it's usually very common to detect insects with weather radar. Sometimes this is actually very useful to meteorologists, too.

    • Why would it be unusual to see migratory birds going from north to south this time of year? That seems like what we'd expect from any migratory creature.

      I'm also confused by this. The butterflies were headed South to Mexico (self-deportation does exist!), and shouldn't any migratory birds traveling through Colorado en masse in September or October also be heading South, more or less? Something isn't adding up here.

      • I have no idea either, but I am willing to speculate: In Colorado, the transition from prairie to mountains is abrupt, and migrating birds will often follow the front range. Migrating insects are not known to navigate using geographic features as guides, and instead tend to follow wind patterns. The birds tend to be strung out in a N-S direction, and the insect swarm is more likely to be a "blob". So maybe that is what makes the pattern look different.

        • Can confirm it's definitely these little guys - they're all over my house the last couple days. It's also going to be a near perfect weekend followed by a very hard freeze and snow on Monday, so there may be some instinctual drive pushing them south along the Front Range.

          • by Bigbutt ( 65939 )

            I've actually had quite a few heading south at my place at 8,200'. Not a swarm but certainly a lot more than I expected to see this time of year.

            [John]

            • Indeed, just leaving work a few days ago when the swarm was first reported, walked by some bushes downtown and a ton of butterflies flew up out of them, never really seen that before downtown

    • Why would it be unusual to see migratory birds going from north to south this time of year?

      . . . are you suggesting that coconuts migrate . . . ? What would be the wind velocity, and could they grab it by the husk . . . ?

    • I've seen mayfly hatches show up on weather radar along the upper Mississippi river. I've also seen them pile up to about 4" (100mm) deep under street lights.

  • ...local high school car washes set fundraising records.

  • Butterflies flap their wings in Denver and radar systems go nuts.

    • Butterflies flap their wings in Denver and radar systems go nuts.

      ..and all without a single weed joke!? We're slipping.

  • by Gravis Zero ( 934156 ) on Saturday October 07, 2017 @12:51AM (#55326241)

    Oh, that's just your mom. ;)

  • When I was in the Navy we would pick up schools of porpoises on the radar. The sea has to be perfectly calm when the school approaches, their splashing looks like a small cloud on the radar screen. The sonar picked them up too, sounds like a basketball game with the guys' sneakers squeaking on the floor.
  • There was a lot of concern about declining numbers of Monarch butterflies a couple years ago, due in large part to a reduction in their food source, milkweed. So a lot of people were planting milkweed around the perimeters of their properties.

    As well, I spend a lot of time on the mountain roads in Northern Pennsylvania. There are often clearings for gas lines that run alongside the dirt roads. Some people or groups have apparently been dropping milkweed seeds along these miles of clearing. This summer h

  • Imagine the butterfly effect [wikipedia.org] with that many butterflies. We know why there's so many tornadoes in the U.S.A. now!

    Why the hell is it called a BUTTER-FLY anyway?

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