Tropical Storm Sandy developed south of Jamaica on Monday, becoming the 18th named storm of a busy Atlantic season that has seen only two hurricanes make landfall.

Sandy was about 395 miles (636 kilometers) south of Kingston, Jamaica, and had winds of 40 mph (64 kph), the National Hurricane Center in Miami said. It is expected to head toward Jamaica and be near or over the island Wednesday, perhaps with winds close to hurricane strength of 74 mph (119 kph).

It’s the third year in a row that the Atlantic basin has had at least 18 named storms, a higher than average year of about 11. Despite the active season, only two hurricanes made landfall. Ernesto struck Mexico in August and Isaac hit Louisiana later that month, both as Category 1 storms. Isaac killed seven people.

Robbie Berg, a hurricane specialist at the NHC, said it is unclear why there have been an above average number of storms during the last few years. He pointed out that of this year’s named storms, most were relatively weak and short-lived. Only one Atlantic storm reached Category 3 status — Michael — and it stayed well out to sea.

“We are not sure if there is any significance,” Berg said.

He compared this year to 2004 and 2005 when there were several storms that caused major damage, including Katrina.

As Sandy strengthened into a tropical storm in the Caribbean, a tropical depression formed far away in the Atlantic. It does not pose any threat to land, but could become a named storm later Monday. If it does, it would be Tony.

The Atlantic storm season began June 1 and runs through Nov. 30.