Shortly before 5:27pm, Tropical Storm Dennis was upgraded to a hurricane by the National Hurricane Center.
A reconnaissance aircraft measured winds of approximately 81 miles per hour.
A hurricane warning is now in effect for Jamaica., the southwestern peninsula of Haiti from the Dominican Republic border westward, and for the Cayman Islands and portions of central and eastern Cuba.
Dennis is moving toward the west-northwest at approximately 14 miles per hour, movement that is expected to continue during the next 24 hours.
A hurricane warning means that hurricane conditions are expected within the warning area within the next 24 hours.
Preparations to protect life and property should be rushed to completion.
At 6pm, the centre of Dennis was located near latitude 16.1 north, longitude 72.5 west or about 315 miles east-southeast of Kingston. Jamaica, and about 335 miles south-southeast of Guantanamo, Cuba.
On this track, Dennis will be centred near Jamaica early on Thursday.
Additional strengthening is forecast during the next 24 hours.
Winds extend outward up to 25 miles from the center, while tropical storm force winds extend outward up to 105 miles
Dennis is expected to produce total rainfall accumulations of between four inches and eight inches over southern Hispaniola, Jamaica, eastern Cuba and the Cayman Islands.
The storm should begin dumping rain on the Cayman Islands late tomorrow afternoon or tomorrow evening. The storm is expected to be a Category 1 when it reaches Cayman.
Dennis is expected to travel 40 miles north of Cayman Brac.
On Grand Cayman, heavy beach erosion is expected for the western area of the island, specifically Seven Mile Beach.
Caycompass.com will update information as it is received.