(1 p.m. EDT) -- Tropical Storm Isaac is heading towards New Orleans, and could intensify into a Category 2 hurricane by early Wednesday -- when it's predicted to make landfall on the seventh anniversary of Hurricane Katrina. Its path prompted the closing of Tampa and Miami homeports over the weekend, both of which reopened yesterday. The closures caused some ships to remain at sea, sparking delays to their subsequent departures.

Isaac, the ninth named storm of the 2012 Atlantic Hurricane Season, is in the Gulf of Mexico today. The tropical storm is now about 225 miles south-southeast of Biloxi, Mississippi, and about 125 miles south-southeast of the mouth of the Mississippi River. Tides and heavy rains are causing flooding in coastal areas, including New Orleans, where a hurricane warning is now in effect and which has declared a state of emergency and is currently evacuating residents. Forecasters say it could dump 11 inches of rain along the coast, with up to 19 inches in isolated locations.

According to the National Hurricane Center's 4 a.m. outlook, maximum sustained wind speeds are at 70 miles per hour, and the storm is moving northwest at about 12 m.p.h. So far, Isaac has forced several itinerary changes.

Cruise Ship Itinerary Changes

Allure of the Seas, which departed from Port Everglades on Aug. 19, is sailing a Western Caribbean itinerary (Falmouth, Jamaica; and Cozumel) instead of an Eastern Caribbean itinerary (Charlotte Amalie, St. Thomas; and Philipsburg, St. Maarten).

Due to weather forecasts for southern Florida, Royal Caribbean has announced that Allure, which was originally due to conclude its current sailing on Sunday, Aug. 26, will stay at sea for two additional days. That means the ship's next sailing will be delayed by two days. The line is asking passengers booked on that voyage to arrive at Port Everglades on Tuesday, Aug. 28, between 11:30 a.m. and 4 p.m. for embarkation. The shortened cruise has resulted in itinerary changes. The new itinerary will include a sea day on Wednesday, a Cozumel call on Thursday, a sea day on Friday and a stop at Nassau on Saturday. Those booked on the upcoming sailing will receive onboard credit and a 10 percent discount on a future cruise. Passengers on the current sailing who booked their flights through Royal Caribbean will be automatically rebooked. Those who booked their travel arrangements independently will have free access to phone lines and the Internet onboard to make new arrangements.

The itinerary for American Queen, a riverboat that sails the Mississippi, will proceed as scheduled, departing from Memphis on Thursday, Aug. 30. Because New Orleans has declared a state of emergency and has begun evacuations, those booked on the sailing who originally planned to fly into New Orleans should alter their travel arrangements to arrive directly in Memphis instead.

Carnival Destiny, departing on a five-night voyage from Miami on Saturday, will stop at Grand Cayman (instead of Ocho Rios) on Monday and Ocho Rios (instead of Grand Cayman) on Tuesday.

Carnival Dream, which will be departing on a seven-night sailing from Port Canaveral on Saturday, will skip its Nassau call on Sunday in favor of a sea day. The ship will now pay a visit to St. Maarten (instead of St. Thomas) on Tuesday and St. Thomas (instead of St. Maarten) on Wednesday, and a sea day originally scheduled for Thursday will be replaced with a call on Grand Turk.

Carnival Imagination is currently sailing on a three-night cruise that departed on Friday and will remain at sea until the port of Miami reopens. Embarkation for the next sailing, a four-night cruise slated to depart on Monday, is expected to begin at 4 p.m., and the voyage is scheduled to depart at 7:30 p.m.

Due to port closures in Tampa, Carnival Legend's current sailing will instead conclude in Port Canaveral at 8 a.m. on Sunday. Passengers leaving the ship, as well as those embarking on the next sailing, will be bused 2.5 hours by complimentary motorcoach between the two ports. The next sailing, scheduled to depart on Aug. 26, will leave Port Canaveral at 8 p.m.

The upcoming itinerary has also been modified. The ship will scrap a call on Cozumel for a sea day on Tuesday. On Wednesday, a call on Belize will be swapped for a call on Grand Cayman, and Friday's call will be Cozumel in place of Grand Cayman. Although the Aug. 26 cruise will depart from Port Canaveral, it will end in Tampa, as scheduled, on Sunday, Sept. 3.

Carnival Sensation's next voyage will sail the following itinerary: a sea day on Monday will replace a previously scheduled call on Freeport; a two-day call on Nassau will be cut short on Wednesday, and a call on Freeport will be substituted for it.

Due to port closures in Miami, Carnival Valor's next scheduled sailing will now operate as a five-night cruise departing Aug. 27, rather than a six-night voyage, departing Aug. 26. The itinerary will include Grand Cayman and Montego Bay. A scheduled call on Key West has been cancelled. Departure time is expected to be at 8 p.m. Passengers who opt to sail on this voyage will receive a one-day prorated refund of their cruise fare and a $50-per-person onboard credit. Those booked also have the option of canceling and receiving a full refund or a future cruise credit equal to the amount of their cruise fare.

Monarch of the Seas and Majesty of the Seas are currently sailing a modified itinerary. The ships, which both departed Friday, will each add an extra sea day on Sunday.

Embarkation for both ships' next sailings will be on Monday, Aug. 27, as originally scheduled. However, Majesty's embarkation time will now be from 5 p.m. to 8 p.m., and Monarch's will begin at 1 p.m., as previously planned. Monarch's itinerary will include a sea day on Wednesday and a stop at CocoCay on Thursday.

Norwegian Gem will change the order of its ports, calling on Great Stirrup Cay on Tuesday, Nassau on Wednesday and Port Canaveral on Thursday.

Norwegian Sky will be at sea Sunday as part of a modified itinerary. The ship is expected to conclude its sailing between noon and 4 p.m. Monday, a few hours later than scheduled. As a result, embarkation for the vessel's next sailing will begin at 5 p.m. Sky is slated to depart by 10 p.m. and follow her original itinerary.

Weather Outlook: Possible Affected Ships and Ports

A hurricane warning (conditions expected within 36 hours) is in effect for part of Louisiana, including New Orleans, through Destin Florida, as well as parts of Alabama. A hurricane watch (conditions possible within 24 to 36 hours) is also in effect for parts of Louisiana.

Additional tropical storm warnings (conditions expected within 36 hours) and watches (conditions possible within 48 hours) are in effect in parts of Florida, Louisiana and Alabama.

--by Dori Saltzman, News Editor; updated by Ashley Kosciolek, Copy Editor