NCL Breakaway has two itineraries from New York in January: A 14-Day Southern Caribbean cruise, and a 14-Day Western Caribbean cruise.
If you are considering the Southern Caribbean itinerary, without saying that you should reconsider, I would like to share with you our 2008 experience cruising from New York. We were on Holland America's ms Noordam, which also left from New York with the first port-of-call being San Juan PR, and also returned from the Leeward Islands to New York. I encourage you to draw a straight line between New York and San Juan, and between Antigua and New York. Both lines make very clear that between New York and the Leeward Islands is... The Atlantic Ocean. The open ocean is prone to rough seas at times. On the Southbound portion of our cruise, the ocean was so rough that it - the movement of the ocean and nothing else - practically emptied the Lido pool.
I don't want to be alarmist. This doesn't happen often, but it happens. Our trip back from the Leeward Islands was rough but the pool stayed filled.
Just something to keep in mind.