A cyclone is a closed-circulation rotating storm that depending on its wind-speed intensity is classified, from weakest to strongest, as a tropical depression, tropical storm or hurricane.
Forecasters expect Oscar to become a hurricane later Sunday as its track curves toward the North Atlantic. Additional strengthening is forecast during the next several days, and Oscar is expected to make a transition to a tropical storm on Sunday.
There are no coastal watches or warnings in effect, according to the agency.
Maximum sustained winds have increased to near 60 miles per hour (95 km/h) with higher gusts.
The 2018 Atlantic hurricane season officially started June 1, and it will end on November 30, the NHC said. Regardless of strength, Hurricane Oscar is not expected to be a threat to land. Tropical-storm-force winds extend outward up to 115 miles from the center.
Tropical Storm Oscar has been upgraded to a hurricane in the central Atlantic.
During the afternoon on Thursday, shower activity associated with the low pressure system became more concentrated.