With maximum sustained winds of 75 km/h, higher gusts and a central pressure dropping to 1003 hP, the storm will continue moving westward.
Formed only a few hours ago, the storm Ian is forecast to reach hurricane status late Sunday or at night.
The storm is located at 14.7 degrees N and 73.7 degrees W, a position that places it in eastern Caribbean waters about 485 km off southeast of Kingston, Jamaica and about 950 km off southeast of Grand Cayman.
Ian is the ninth tropical storm of the current hurricane season and the sixth formed in September, preceded by Danielle, Earl, Fiona, which became hurricanes.
pll/mem/alb