If your asking about Hurricanes, then you should be safe. Hurricane season doesn't begin until mid to late June. (Even last years record hurricane season's first tropical storm wasn't until the the 8th of June and the first Hurrican (Cindy) was on the 3-7th of July. Your cruise the first week of May should be safe.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007