Experts say Key West radar detected a sure sign that spring is around the corner
By
Lauren Fox, AccuWeather staff writer
Published Feb 20, 2020 9:58 PM EDT
With the spring equinox less than a month away, nature is showing signs of the changing seasons already. Earlier this week, Florida radar data revealed a hint of the warmer months to come. The National Weather Service (NWS) Key West meteorologists called radar images "the most impressive display of migratory birds so far this year."
In a gif tweeted by the NWS Key West on Monday, Feb. 17, a weather radar is shown to have picked up a large flock of birds -- appearing as a yellow and green mass -- heading back north after staying in areas south of the Sunshine State for the duration of the winter.
Lead forecaster at the NWS Key West Chris Rothwell told AccuWeather that northern bird migration starts around January and goes throughout the summer.
"Generally speaking, in spring, birds are looking for warm and moist air masses, with at least some tail wind support," according to Andrew Farnsworth, a research associate at The Cornell Lab of Ornithology. In fall, he said they seek the reverse.
In January, the temperature in Florida was 3.4 degrees Fahrenheit above normal, and February has continued this warm trend.
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Farnsworth told AccuWeather in an email that a hotter-than-average winter season as a whole has affected the migration of birds, but the birds detected on the radar would remain unaffected. He explained that the birds traveling from Cuba are "obligatory migrants" that travel on a clock rather than as a reaction to the temperature. Instead, they know to migrate based off things like the changes in day lengths that come with changing seasons.
“A lot of birds can be the size of hail, and so we can pick up what we call ‘non-meteorological objects,’” he said, which includes birds, insects, bats and even diesel smoke coming off ships.
Rothwell said the way forecasters tell birds apart from clouds or precipitation is a combination of the time of day the objects are captured and the shape of the pattern that indicates it is a swarm of birds taking off.
Radars work by sending out a pulse of energy, which then encounters particles and objects in the air. Some of that energy bounces back and returns to the radar, and the data is then analyzed by a computer.
A flock of birds migrating north caught on radar (National Weather Service Key West)
Birds show up on radar as very bright objects, Rothwell said, because the radar is extremely sensitive and it can pick up things like cloud droplets.
Using a newer technology called Dual-Pol that was introduced in the late 2000s and early 2010s, meteorologists can see even more detail, such as water content and the uniformity that a mass is moving in. Dual-Pol radar is different from past radar technology as it receives information from both horizontal and vertical pulses, in addition to the size of objects that radar pulses reach.
Prior to Dual-Pol, forecasters had only the brightness of an object and the direction in which it's moving, according to Rothwell. He said insects move in much more uniform groups than birds, which is one way they are able to tell the two apart.
Rothwell said the best conditions to be able to pick these things up on radar is when there is an inversion -- meaning the atmosphere's temperature increases with height.
He said bird migration is detected on radar about 75 percent of the year.
In February, palm, pine and yellow-throated warblers, some songbird species and great egrets are among the birds that begin passing through Florida during their northward migration, Farnsworth said, adding the birds seen on radar could have been waterbirds like great egrets and belted kingfishers or land birds like yellow-bellied sapsuckers and northern flickers. There were probably between 500 and 1,000 birds per hour per km in the area at the time the radar picked them up.
A belted Kingfisher in Pennsylvania (iStock / Getty Images Plus / Harry Collins)
“Unless it's the winter or summer solstice, birds are always on the move," Rothwell said. "As soon as we get past the winter solstice, birds start moving back north.”
Rothwell said Florida is a "fly-over state," meaning its habitat essentially allows it to act as a rest stop for migrating birds to rest and refuel on their long journeys, especially for birds leaving Cuba as they travel north.
Peak movement in the Gulf of Mexico area occurs between April 19 and May 7, in which 1 billion birds pass through, Farnsworth said, making it 50 percent of migration traffic as a whole.
"The number of birds represented in this radar imagery pales in comparison to what's to come, and what does come, every spring," Farnsworth said.
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.
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News / Weather News
Experts say Key West radar detected a sure sign that spring is around the corner
By Lauren Fox, AccuWeather staff writer
Published Feb 20, 2020 9:58 PM EDT
With the spring equinox less than a month away, nature is showing signs of the changing seasons already. Earlier this week, Florida radar data revealed a hint of the warmer months to come. The National Weather Service (NWS) Key West meteorologists called radar images "the most impressive display of migratory birds so far this year."
In a gif tweeted by the NWS Key West on Monday, Feb. 17, a weather radar is shown to have picked up a large flock of birds -- appearing as a yellow and green mass -- heading back north after staying in areas south of the Sunshine State for the duration of the winter.
Lead forecaster at the NWS Key West Chris Rothwell told AccuWeather that northern bird migration starts around January and goes throughout the summer.
"Generally speaking, in spring, birds are looking for warm and moist air masses, with at least some tail wind support," according to Andrew Farnsworth, a research associate at The Cornell Lab of Ornithology. In fall, he said they seek the reverse.
In January, the temperature in Florida was 3.4 degrees Fahrenheit above normal, and February has continued this warm trend.
CLICK HERE FOR THE FREE ACCUWEATHER APP
Farnsworth told AccuWeather in an email that a hotter-than-average winter season as a whole has affected the migration of birds, but the birds detected on the radar would remain unaffected. He explained that the birds traveling from Cuba are "obligatory migrants" that travel on a clock rather than as a reaction to the temperature. Instead, they know to migrate based off things like the changes in day lengths that come with changing seasons.
“A lot of birds can be the size of hail, and so we can pick up what we call ‘non-meteorological objects,’” he said, which includes birds, insects, bats and even diesel smoke coming off ships.
Rothwell said the way forecasters tell birds apart from clouds or precipitation is a combination of the time of day the objects are captured and the shape of the pattern that indicates it is a swarm of birds taking off.
Radars work by sending out a pulse of energy, which then encounters particles and objects in the air. Some of that energy bounces back and returns to the radar, and the data is then analyzed by a computer.
A flock of birds migrating north caught on radar (National Weather Service Key West)
Birds show up on radar as very bright objects, Rothwell said, because the radar is extremely sensitive and it can pick up things like cloud droplets.
Using a newer technology called Dual-Pol that was introduced in the late 2000s and early 2010s, meteorologists can see even more detail, such as water content and the uniformity that a mass is moving in. Dual-Pol radar is different from past radar technology as it receives information from both horizontal and vertical pulses, in addition to the size of objects that radar pulses reach.
Prior to Dual-Pol, forecasters had only the brightness of an object and the direction in which it's moving, according to Rothwell. He said insects move in much more uniform groups than birds, which is one way they are able to tell the two apart.
Rothwell said the best conditions to be able to pick these things up on radar is when there is an inversion -- meaning the atmosphere's temperature increases with height.
Related:
He said bird migration is detected on radar about 75 percent of the year.
In February, palm, pine and yellow-throated warblers, some songbird species and great egrets are among the birds that begin passing through Florida during their northward migration, Farnsworth said, adding the birds seen on radar could have been waterbirds like great egrets and belted kingfishers or land birds like yellow-bellied sapsuckers and northern flickers. There were probably between 500 and 1,000 birds per hour per km in the area at the time the radar picked them up.
A belted Kingfisher in Pennsylvania (iStock / Getty Images Plus / Harry Collins)
“Unless it's the winter or summer solstice, birds are always on the move," Rothwell said. "As soon as we get past the winter solstice, birds start moving back north.”
Rothwell said Florida is a "fly-over state," meaning its habitat essentially allows it to act as a rest stop for migrating birds to rest and refuel on their long journeys, especially for birds leaving Cuba as they travel north.
Peak movement in the Gulf of Mexico area occurs between April 19 and May 7, in which 1 billion birds pass through, Farnsworth said, making it 50 percent of migration traffic as a whole.
"The number of birds represented in this radar imagery pales in comparison to what's to come, and what does come, every spring," Farnsworth said.
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.
Report a Typo