Late-season tropical threat taking shape in the Caribbean, forecasts show

A new tropical threat is taking shape in the western Caribbean and will likely become the 18th named storm of the busy Atlantic hurricane season within the next 24 hours, forecasts show.

The tropical system, currently located in the western Caribbean, is expected to develop into Tropical Storm Sara by Thursday afternoon -- just weeks before the official end of the Atlantic hurricane season on Nov 30.

The National Hurricane Center issued advisories Wednesday for the development of the potential tropical cyclone. Hurricane watches are in effect now over portions of Honduras, with tropical storm watches for portions of Nicaragua.

The storm is expected to bring heavy rain and gusty winds to places like Jamaica and the coasts of Honduras and Nicaragua over the next 24 to 48 hours. It will then strengthen even more, with the potential for wind speeds to increase to near hurricane status.

The system is forecast to meander in the western Caribbean over the weekend, when it will bring heavy rain to Central America.

"The conditions are definitely favorable for this storm to get its act together," Marshall Shepherd, director of the Atmospheric Sciences Program at the University of Georgia and former president of the American Meteorological Society, told ABC News.

"This is definitely a storm we've got to keep an eye on," Shepherd added.

By Monday, the system will be on the move and is forecast to pass over Mexico's Yucatán Peninsula, potentially impacting popular resort towns such as Cancun and Tulum. On the current track, landfall is expected sometime on Monday near Belize and the Yucatán Peninsula as a tropical storm.

It is still too soon to determine what the system will do once it impacts the Yucatán Peninsula. The interaction with land could significantly weaken the system and influence its future trajectory. Some forecast models suggest the system could then move into the Gulf of Mexico, but it's too early to realistically speculate such details.

The Atlantic hurricane season officially runs from June 1 to Nov. 30 and has not only brought above-average activity, but several high-impact storms.

Florida's Gulf Coast has already been inundated with devastating hurricane impacts in recent months. In late September, Hurricane Helene struck Florida's Big Bend before causing deadly flash flooding in Asheville, North Carolina. Weeks later, Hurricane Milton made landfall just south of Tampa Bay, bringing deadly storm surge to the Gulf Coast but also generating record-breaking tornado activity in southeast Florida.

Tropical systems that develop in November tend to be more in the western part of the tropical Atlantic, including the western Caribbean and the Gulf of Mexico, Jennifer Francis, an atmospheric scientist at the Woodwell Climate Research Center, told ABC News last month. The warm ocean temperatures could help increase the likelihood of a tropical cyclone forming this late in the season, Francis said.

While rare, it's not outside the realm of possibility for tropical systems to form outside of the traditional hurricane season, records show.

In December 2005, Hurricane Epsilon and Tropical Storm Zeta were churning in the Atlantic Basin after the official hurricane season had concluded. Hurricane Alex in 2016 was an "unusual" tropical cyclone that formed in January, according to NOAA.

The peak of the Atlantic hurricane season is Sept. 10, according to the National Hurricane Center, but the majority of tropical activity came a little later this year. Hurricane Helene formed on Sept. 24 and Hurricane Milton on Oct. 5.

"When we have an active season, as we were projected to have this year, it's not unusual to go into November with storms," Shepherd said.

ABC News' Max Golembo and Mel Griffin contributed to this report.