A sharpening weather system slogged south of the Lower Keys on Sunday, belting the islands with blustery rain that for many nevertheless felt like an average soggy August day.
On Duval Street in Key West, business was slow for merchants. But the mood remained nonchalant even as the sunny morning gave way to gray and the winds picked up in the afternoon.
“I would say it’s par for the course,” said bartender Kat Hayes of the Cork & Stogie wine-and-cigar shop on Duval Street.
Said an employee at the Key Lime Pie Bakery: “It’s slow on the island. I think a lot of people watched the media and bought into it. It’s just a typical rainy day in the tropics.”
Still, the weather system had strengthened enough by Sunday evening that the National Hurricane Center began issuing public advisories — a storm-hunting plane outfitted with scientific instruments detected a more well-defined core as it threaded the Florida Straits.
Scientists upgraded the system to a tropical depression and forecast that it would grow into a tropical storm sometime Monday as it churned into the warm waters of the Gulf of Mexico.
As of 8 a.m. Monday, the system was producing winds of nearly 35 miles an hour and could produce up to 4 inches of rain throughout the Keys and the southern half of Florida.
“This rainfall may cause flooding and flash-flooding,” hurricane specialist Michael Brennan wrote in his advisory.
With computer models all over the map, Florida and other Gulf Coast states may have to continue monitoring it well into the coming week. The National Hurricane Center predicted the storm would take a decidedly northern turn while in the middle of the Gulf on Tuesday, with the Panhandle in its possible trajectory.
Back in South Florida, rain was the main concern on Sunday.
While much of South Florida will see scattered storms, the National Weather Service in Miami predicted that the heaviest rain — up to 3.5 inches over several days — would be in the Keys, Everglades National Park and the southern part of Miami-Dade County.
The soggy conditions could persist into the early week, with the service increasing Miami’s rain chances from 70 percent Sunday to 80 percent Monday and early Tuesday as the system pulls in moisture from the tropics.
Authorities were not taking any chances.
Fearful that the storm could “spin up quickly,” Dry Tortugas National Park closed in advance of the storm and will remain closed until it passes, park officials said. Boats will still be allowed to cross park waters and seek shelter in Garden Key and Bird Key harbors, but no services or emergency responses will be available.
Everglades National Park will remain open, but the Flamingo campground closed Saturday night and back-country camping was shut down for Sunday. Park officials also urged visitors to check weather reports before heading to the park since the storm could trigger local flooding.
“Residents and visitors in South Florida and the Florida Keys should remain prepared for gusty winds and heavy rainfall through Tuesday,” Gov. Rick Scott tweeted on Sunday.
Key West, where crews had trimmed trees in advance and were on call to clear debris from the streets, figures to be most affected.
“We’re expecting a period of heavy rains overnight,” National Weather Service Key West meteorologist Adam Futterman said on Sunday. “We could see some local street flooding in Key West.”
For some businesses such as the Bike Man bike-rental shop, Sunday’s conditions actually felt better than the day before, when persistent squalls blew over Key West. But that’s nothing new this time of year, said owner Tom Tyson.
“It’s to be expected, especially after kids go back to school. It’s not a big deal. We just hope no big storms hit and that we’ve saved enough money to get us through,” he said.
He added, laughing: “What do I know? I’m just the bike man, not the weatherman.”