CORAL GABLES, Fla. (AP) _ The 1986 Atlantic hurricane season opened quietly Sunday as forecasters reported little activity in the storm zone that produced six hurricanes and two tropical storms last year.

Meanwhile, a Colorado State University expert predicted that there would be fewer than normal hurricanes this season in the Atlantic Basin, which includes the Atlantic Ocean, Caribbean Sea and Gulf of Mexico.

Forecasters Sunday were keeping an eye on a tropical disturbance that developed last week and has since moved across Central America, leaving heavy thunderstorms in its wake in the western Caribbean.

''We've been watching it for a while and it shows no sign of development,'' said Miles Lawrence, a specialist with the National Hurricane Center here.

The thunderstorms Sunday afternoon were extending over open water south of Cuba and Jamaica and were expected to remain stationary, he said.

Between now and Nov. 30, the official end of the hurricane season, forecasters will monitor about 100 weather disturbances that all have the possiblity of growing into major disturbances, Lawrence said.

Peak months for activity will be August, September and October, Lawrence said.

During the 1985 hurricane season, when six hurricanes and two tropical storms battered the Atlantic and Gulf coasts, it was not until the middle of July that a tropical disturbance developed into Tropical Storm Ana, the first named storm of the season.

In Fort Collins, Colo., atmospheric scientist William M. Gray said Sunday that he expected four hurricanes this season compared with the average six.

Gray, who last year accurately forecast the number of hurricanes, also predicted a total of eight hurricanes and tropical storms compared with an average of 10, and 15 hurricane days compared with the average of 25.

He said he based his hurricane forecast on the Pacific Ocean current off the coast of South America known as El Nino, the expected direction of equatorial winds 13 miles to 22 miles high and sea level pressures in the Caribbean and Gulf of Mexico.