Subtropical Storm Nicole Forecast to Become Hurricane as It Nears Florida

Subtropical Storm Nicole quickly took aim at land after it formed in the southwestern Atlantic on Monday, prompting a hurricane warning for portions of the northwestern Bahamas and a watch along the east coast of Florida as forecasters said it could reach hurricane strength by midweek.

Nicole was forecast to approach the northwestern Bahamas on Tuesday, when it was expected to strengthen and move near or over those islands on Wednesday, meteorologists said. The storm, which was packing 45-mile-an-hour winds on Monday evening, will head toward Florida’s east coast as a hurricane by Wednesday night.

In preparation, the government of the Bahamas issued a hurricane watch that was upgraded on Monday afternoon to a hurricane warning for the northwestern Bahamas, according to the National Hurricane Center. Three to five inches of rain were expected across the northwest Bahamas and central and northern parts of Florida from Tuesday through Thursday, with up to seven inches possible in some locations.

The warning, which means that hurricane conditions were expected within 36 hours, included Abaco, Berry, Bimini and Grand Bahama islands. A tropical storm warning, anticipating tropical storm conditions, was in effect for Andros, New Providence and Eleuthera islands.

In the United States, a hurricane watch, anticipating possible hurricane conditions within 48 hours, was issued for the east coast of Florida, from the Volusia-Brevard County line to Hallandale Beach, north of Miami in Broward County, and for Lake Okeechobee in the southern part of the state.

A storm surge watch was upgraded to a storm surge warning from North Palm Beach north to Altamaha Sound in Georgia. A storm surge watch was in effect south from North Palm Beach to Hallandale Beach.

A tropical storm warning was in effect from Altamaha Sound south to Hallandale Beach and Lake Okeechobee.

Meteorologists said they did not expect Nicole to have much of an impact in Florida until after Tuesday, when voters in Florida and Georgia, and the rest of the United States, will cast ballots in the midterm election.

The storm is expected to strengthen into a Category 1 hurricane as it approaches the Florida peninsula, said Jamie Rhome, acting director of the National Hurricane Center in Miami. “The worst of the impact will be coming onshore during the day on Wednesday, and possibly lingering on Thursday,” Mr. Rhome said.

It is expected to “go across the state and then hook back,” he said. The timing was not immediately clear, but that trajectory means that “regardless of where the center tracks, a good portion of the Florida peninsula will feel some of the impact” of wind and rain from the storm, Mr. Rhome said.

Gov. Ron DeSantis of Florida on Monday declared a state of emergency for 34 counties that could be in the path of the storm, authorizing the state’s emergency management division to pursue emergency measures and seek federal assistance.

“While this storm does not, at this time, appear that it will become much stronger, I urge all Floridians to be prepared and to listen to announcements from local emergency management officials,” Mr. DeSantis said in a statement.

Nicole is the third named storm to form in the Atlantic since Halloween and the second this month.

“This is the most Atlantic named storms to form between October 31 - November 7 on record,” Phil Klotzbach, a senior research scientist at Colorado State University, said on Twitter on Monday.

And although it may seem rare to have a named storm this late in the hurricane season, which runs from June 1 to Nov. 30, half of the seasons since 1966 have had at least one named storm form in November, Mr. Klotzbach said.

There is a chance of tying the November record set in 2001 for named storms if another area that the National Hurricane Center is monitoring in the Central Atlantic becomes a named storm. This area could become strong enough for a name — it would be called Owen — once it “starts moving northeast, away from the extremely robust outflow from Nicole’s large-scale circulation,” Mr. Klotzbach said.

A subtropical storm is similar to a tropical storm in intensity but typically does not have a complete warm core center like a tropical storm. The wind field is not nearly as symmetrical as a tropical storm, and the wind field is usually much more expansive.

Nicole’s winds stretch out 310 miles from the center of the storm, according to a 10 p.m. Eastern update from the Hurricane Center.

“We are going to have a really big wind field,” John Cangialosi, a senior hurricane specialist at the National Hurricane Center, said in an interview.

Tropical storm-force winds will be felt all along the east coast of Florida, with a smaller core of hurricane-force winds near the center of the storm.

The widespread strong winds pose a dual threat of dangerous winds and flooding.

The links between hurricanes and climate change have become clearer with each passing year. Data shows that hurricanes have become stronger worldwide during the past four decades. A warming planet can expect stronger hurricanes over time, and a higher incidence of the most powerful storms — though the overall number of storms could drop, because factors like stronger wind shear could keep weaker storms from forming.

Hurricanes are also becoming wetter because of more water vapor in the warmer atmosphere. Also, rising sea levels are contributing to higher storm surge — the most destructive element of tropical cyclones.

Víctor Manuel Ramos, April Rubin and Derrick Bryson Taylor contributed reporting.