Caribbean under hurricane watch again. Tropical Storm Maria following Irma’s track.

Tropical Storm Maria formed in the Atlantic Saturday, threatening to pound islands already hit hard by Irma with another hurricane early next week.

In an update at 5 a.m. Sunday, a hurricane watch was issued for Dominica. The storm was 460 miles from the Lesser Antiles, moving west-northwest at 15 mph with sustained winds of 65 mph.

National Hurricane Center forecasters said Maria will likely bring dangerous wind, storm surge and heavy rain to parts of the Lesser Antilles and could reach the Leeward Islands as a hurricane early next week. Maria could become become a major hurricane by Tuesday night, reach Puerto Rico Wednesday night and the Dominican Republic on Thursday night.

On Saturday night, hurricane watches were issued for Antigua, Barbuda, St. Kitts, Nevis, Montserrat, Guadeloupe, Saba and St. Eustatius, St. Martin and Anguilla. Tropical storm watches were issued for other islands in the chain.

The forecasters warned rainfall accumulation in the Leeward Islands through Tuesday night could “cause life-threatening flash floods and mudslides.”

The Coast Guard captain of the Port of San Juan warned that sustained gale force winds greater than 39 miles per hour may arrive within 72 hours, and advised pleasure craft “to seek safe harbor.”

It’s not yet clear what impact Florida and the U.S. might face from the storm. Model projections so far out can often be hundreds of miles off. But an early run of the European model — which reliably tracked Irma — takes the storm toward Florida.

The system became much better organized throughout Saturday, forecasters said, as it moved over warm tropical waters and encountered light wind shear. Air around the storm is also very moist. Those conditions shouldn’t change in the coming days, they said, likely allowing Maria to continue to pick up steam.

The storm is now moving along the outside of a high pressure ridge. But that ridge is expected to weaken. That should slow the storm and cause it to head to the northwest.

In his Saturday blog, Weather Underground meteorologist Jeff Masters said the storm could approach the United States “more than a week from now.”

Masters said the storm’s path could be influenced by Hurricane Jose, currently hundreds of miles east of Florida and moving toward the coast of New England. If Jose weakens the high pressure ridge steering the storm, it could allow Maria to head more to the northwest or north-northwest, he said. If not, the storm will likely keep heading to the west-northwest.

An autumn trough moving across the United States, he said, could also strengthen a ridge in the northeast, preventing the storm from moving out to sea.

Miami Herald staff writer Carol Rosenberg contributed to this report.

This story was originally published September 16, 2017 at 5:16 PM with the headline "Caribbean under hurricane watch again. Tropical Storm Maria following Irma’s track.."