First off, AJ is right that only the cruise line itself can advise you correctly for your actual cruise. So, put their number on speed-dial and check in frequently for the status.
However, these ships are in their home port only briefly to exchange passengers. If a storm were to prevent departure from a port, it may also prevent docking to that same port! Thus, if Earl makes landfall at your departure point, your ship may have to remain clear from the dock until the bad weather passes. In this situation, the vacationers before you get an extra day (which they might not enjoy, missing flights) and your departure would be delayed.
The ships generally change their itinerary at sea to avoid the storms, so once on board and sailing, do not worry. You may miss out on certain stops, but that is the risk of sailing at this time of year (and the reward of cheaper rates).
BTW, Reuters just posted this notice:
"Earlier, the hurricane buffeted the northernmost Leeward Islands of the Caribbean with fierce winds, driving rain and pounding waves as it passed.
The world's three largest cruise lines -- Carnival Corp, Royal Caribbean and Norwegian Cruise Line -- changed their Caribbean itineraries and rerouted at least seven ships to avoid the storm."