Cat 5 storm in the open ocean. Big deal.
It’ll be days and much weaker when it finally hits land again in Jamaica.
They get stronger in open ocean, not weaker.
It will weaken as it gets closer to land. Just how much depends on forward storm speed.
Since it’s hitting perpendicular to the coast, it won’t weaken as much as it would if it went parallel to the coast for a bit before making landfall.