MIAMI — Subtropical storm Andrea, the first named storm of the Atlantic season, has formed a few hundred miles southwest of Bermuda.

The National Hurricane Center on Monday said Andrea has a “well-defined center,” with maximum sustained winds of about 40 mph. Monday evening, the storm was centered about 335 miles southwest of Bermuda in the western Atlantic and moving northward at 14 mph.

Although there are no coastal watches or warnings in effect, the Miami-based center warned that people in Bermuda should monitor the storm’s progress for the next few days.

Meteorologists say the storm could strengthen a little overnight, but Andrea is expected to weaken late today and dissipate on Wednesday as it’s absorbed into a cold front. While the storm may affect Bermuda, it will pose no threat to the mainland United States or Virgin Islands.

Tropical cyclones are classified by their wind speed, from tropical depression to tropical storm to hurricane.

A subtropical storm is one with a windspeed of at least 39 mph. A subtropical storm tends to be drier and less intense than a tropical storm. It lacks the potential to strengthen into a hurricane unless it moves over warmer waters and becomes a tropical storm.

Though the official start of hurricane season is about two weeks away, it’s not unusual to have a system being watched by the hurricane center before that time.

Hurricane season begins June 1 and runs through Nov. 30, with the peak period for storms coming in August and September. Early forecasts call for an average to slightly below average season.