Tropical Storm Bret, which formed on Monday as the second named storm of the 2023 Atlantic hurricane season, headed toward the Lesser Antilles, and for the rest of the week it is forecast to intensify but remain a tropical storm and not become a hurricane, the National Hurricane Center said.

Bret formed nearly 1,300 miles east of the southern Windward Islands and by late Tuesday night was about 730 miles away, moving west at 17 miles per hour toward the tropical Atlantic. “This general motion is expected to continue for the next several days,” the National Hurricane Center said.

The storm had initially been forecast to become the first hurricane of the 2023 Atlantic season and is expected to be near hurricane strength when it blows into some eastern Caribbean islands on Thursday.

Maximum sustained winds reached 50 miles per hour late Tuesday, up from 40 miles per hour in the morning. A tropical storm watch was in effect for Barbados, Dominica, Martinique and St. Lucia, where it posed a “high threat,” the center said.

The storm is forecast to reach the Lesser Antilles on Thursday and then move across the island, with a risk of flooding from heavy rainfall, strong winds and dangerous waves, the center said. It urged anyone in the Lesser Antilles, Puerto Rico and the Virgin Islands to closely monitor the storm and be prepared.

“Landslides are highly likely, as we are coming out of a relatively dry period where grounds may be compromised or developed cracks,” Fitzroy Pascal, Dominica’s national disaster coordinator, told The Associated Press.

The storm’s track is uncertain, though, and it is unclear which islands could expect to receive the worst impact. Rain, strong winds and storm surges could happen in the Lesser Antilles, Puerto Rico and the Virgin Islands, but Bret is expected to weaken after it moves into the Caribbean.

Rain is expected through Saturday morning. About four to six inches is anticipated across parts of Lesser Antilles, extending from Guadeloupe to as far south as St. Lucia. The islands of Barbados and St. Vincent and the Grenadines may experience two to four inches of rainfall.

Another storm system similar to Bret is following on its heels and may develop into Cindy, the season’s third named storm, later this week. Tropical storms earn a name once they have sustained winds of 39 m.p.h. Once winds reach 74 m.p.h., a storm becomes a hurricane, and at 111 m.p.h. it becomes a major hurricane.

Bret is the third tropical cyclone to reach tropical storm strength this year. The National Hurricane Center said in May that it had reassessed a storm that formed off the northeastern United States in mid-January and determined that it was a subtropical storm, making it the Atlantic’s first cyclone of the year. However, the storm was not retroactively given a name, making Arlene, which formed in the Gulf of Mexico on June 2, the first named storm in the Atlantic basin this year.

The Atlantic hurricane season started on June 1 and runs through Nov. 30.

In late May, the National Oceanic and Atmospheric Administration predicted that there would be 12 to 17 named storms this year, a “near-normal” amount. There were 14 named storms last year, after two extremely busy Atlantic hurricane seasons in which forecasters ran out of names and had to resort to backup lists. (In 2020, there were a record 30 named storms.)

However, the NOAA did not express a great deal of certainty in its forecast this year, saying there was a 40 percent chance of a near-normal season, a 30 percent chance of an above-normal season and a 30 percent chance of a below-normal season.

There were indications of above-average ocean temperatures in the Atlantic, which could fuel storms, and the potential for an above-normal West African monsoon. The monsoon season produces storm activity that can lead to some of the more powerful and longer-lasting Atlantic storms.

This year also features El Niño, which arrived this month. The intermittent climate phenomenon can have wide-ranging effects on weather around the world, including a reduction in the number of Atlantic hurricanes.

In the Atlantic, El Niño increases the amount of wind shear, or the change in wind speed and direction from the ocean or land surface into the atmosphere. Hurricanes need a calm environment to form, and the instability caused by increased wind shear makes those conditions less likely. (El Niño has the opposite effect in the Pacific, reducing the amount of wind shear.) Even in average or below-average years, there is a chance that a powerful storm will make landfall.

As global warming worsens, that chance increases. There is solid consensus among scientists that hurricanes are becoming more powerful because of climate change. Although there might not be more named storms overall, the likelihood of major hurricanes is increasing.

Climate change is also affecting the amount of rain that storms can produce. In a warming world, the air can hold more moisture, which means a named storm can hold and produce more rainfall, like Hurricane Harvey did in Texas in 2017, when some areas received more than 40 inches of rain in less than 48 hours.

Researchers have also found that storms have slowed down, sitting over areas for longer, over the past few decades.

When a storm slows down over water, the amount of moisture the storm can absorb increases. When the storm slows over land, the amount of rain that falls over a single location increases; in 2019, for example, Hurricane Dorian slowed to a crawl over the northwestern Bahamas, resulting in a total rainfall of 22.84 inches in Hope Town during the storm.

Other potential effects of climate change include greater storm surge, rapid intensification and a broader reach of tropical systems.

Rebecca Carballo, Orlando Mayorquin, Livia Albeck-Ripka and Derrick Bryson Taylor contributed reporting.