The system, which would be named Dorian, could bring bouts of showers to Palm Beach County on Saturday
Three systems simmered in the Atlantic basin Friday after a sleepy tropics jolted awake this week with the ringing of an atmospheric alarm clock.
One of the spins of low pressure meandered Friday just east of South Florida and is expected to become a tropical depression Saturday as it skims the coast heading north toward a more encouraging environment.
The system, which would be named Dorian if it earns tropical storm status, could bring bouts of showers to Palm Beach County on Saturday, but meteorologists wrestled Friday with how much rain would fall on South Florida.
"The uncertainty with this forecast is much higher than normal and it’s frustrating because you want to be able to tell people how to prepare," said Todd Kimberlain, senior meteorologist with the South Florida Water Management District. "But this is not a slam dunk."
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Aug 23: A tropical disturbance approaching South Florida will bring periods of showers and thunderstorms across the region today. Heavy rainfall with high rainfall rates may lead to some urban flooding across the region today. Turn Around Don't Drown #FLwx pic.twitter.com/zgdQlYp0Mh— NWS Miami (@NWSMiami) August 23, 2019
Potential rain totals through the weekend from disturbance on our doorstep. https://t.co/VkdsNe59Uj pic.twitter.com/KU0mxSEfJZ— Kimberly Miller (@KMillerWeather) August 23, 2019
The National Weather Service in Miami said as much as three inches of rain is possible along coastal Palm Beach County through Monday. Less is likely if the disturbance stays off the coast, but it’s unclear how much moisture might be trailing behind it. Treasure Coast counties could see higher rain amounts.
"It’s a little muddy for something that is happening right now," said NWS meteorologist Arlena Moses. "We’re not going to see a washout, but passing showers and storms are likely."
An elevated risk of rip currents is possible through the weekend.
August 20 generally marks the beginning of peak hurricane season, and a punctual Mother Nature didn’t disappoint.
Late Tuesday, a now-fizzled Tropical Storm Chantal formed in the far North Atlantic after having just a 10 percent chance of development earlier in the day.
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As of the Friday 8 p.m. forecast from the National Hurricane Center, the system hugging South Florida had a 90 percent chance over five days of becoming Dorian. Its 48-hour chances were 70 percent. National Hurricane Center forecasters cautioned that the southeast coast of the U.S. should keep an eye on the progress of the system. An Air Force Reserve Hurricane Hunter plane is scheduled to investigate it Saturday.
About 1,100 miles east-southeast of the Windward Islands, another budding area of low pressure was given a 70 percent chance of development over five days.
The next name on the 2019 storm list is Erin.
Michael Ventrice, a meteorological scientist with The Weather Company, an IBM business, said a traveling pulse of atmospheric energy called a Kelvin wave is likely to blame for the abrupt burst of tropical systems.
The waves, which travel west to east through the stratosphere, can increase moisture levels in the air and reduce storm-thwarting wind shear. Tropical waves moving west off of Africa can blossom into tropical cyclones when a Kelvin wave passes.
"We are ramping up to our chronological peak of activity," said Ventrice, who predicts the disturbance off Florida could become a hurricane when it pulls away from the state and moves across the warm Gulf Stream.
For South Florida, the would-be Dorian is putting rain chances Saturday at 60 percent, increasing to 70 percent on Sunday. The rain will do little to cool off temperatures, with both days forecast to reach highs near 90 degrees and lows in the upper 70s.
Some flooding is possible where rain bands stall, Moses said.
Coastal Palm Beach County has gotten nearly eight inches of rain this month, which is two inches above normal, according to the water management district.
The official National Weather Service gauge at Palm Beach International Airport was up to 10.3 inches for the month on Thursday. That’s 4.8 inches more than average.
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"We’ve been really saturated with the locally heavy rainfall, but we have a little room because it’s been a little drier for a week," Moses said.
The hurricane season was unusually quiet before this week with Subtropical Storm Andrea forming in May and Hurricane Barry in mid-July.
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Kimberlain, a former National Hurricane Center forecaster, also attributed the flurry of tropical activity this week to a passing Kelvin wave.
"If we get Dorian from this system in the Bahamas, that’s two tropical cyclones in short order," he said. "August 20 tends to be a date of importance because around that day and going to September 10, every day that passes there is an increasing chance of seeing more tropical cyclones."