OT,
Likely if a named storm is in the region a ship is scheduled to cruise, alternate itineraries are already in place. Fantasy cruises to Progreso and Cozumel. If there is a storm in that area the ship will likely be diverted to say Key West and or somewhere in the Bahamas for example. Check with Carnival often. They will post any affected cruises on their site under "Tropical Update". Unless it's at the last minute, then they'll inform you prior to or once on board. It's all they can do in that situation.
To be fair they will always try to make the best decision. What is safest for the passengers, crew and the safety of the vessel is their primary concern. If the vessel is comprimised then so are all onboard. I do know Carnival will attempt deliver the scheduled itinerary as promised. Keep an open mind and remember if a change is made, it's for your and your fellow passengers safety and well being. Be forgiving, Any cruise line is at the mercy of Mother Nature.
Wishing you all smooth sailing.
CD
PS The Gulf is a nasty place to get in a tropical storm or worse, a hurricane. I know first hand. Even a strong cold front can make the Gulf miserable for most cruisers and crew.