FACTBOX: Possible scenarios for Hurricane Gustav

(Reuters) - As Hurricane Gustav marches across the Gulf of Mexico for its eventual collision with the U.S. Gulf Coast on Monday, its strength and where it makes landfall are still moving targets. Here are some possible scenarios on what happens next:

STRENGTH: Some weather forecasters are still predicting Gustav will hit the Gulf Coast as a damaging Category 4 hurricane with wind speeds of up to 155 mph (249 kph). Others point out the storm lost strength over Cuba and its relatively fast movement across the Gulf of Mexico could deprive it of the ability to gather energy and speed from warm water, making it a Category 3 storm.

The storm is expected to come ashore west of New Orleans in the early hours of Monday, and the Louisiana coast could begin to see rains and wind from the sweeping storm on Sunday evening, according to the U.S. National Hurricane Center.

In comparison, Katrina was a catastrophic Category 5 storm -- the highest on the five-step rating scale -- as it moved across the Gulf of Mexico and made landfall as a Category 3 storm.

LANDFALL: The storm's current track also makes it hard to predict where it will strike the coast. New Orleans' evacuation has been center-stage, but Gustav's "cone of uncertainty" means it could hit anywhere from South Texas to the Alabama-Mississippi border. On Sunday morning, the storm was about 325 miles southeast of the mouth of the Mississippi River.

The storm's wide sweep puts the majority of the U.S. oil patch in the cross hairs. The Gulf of Mexico produces about a quarter of U.S. energy supply, and about one-third of U.S. capacity to refine crude oil into gasoline, jet fuel and other essential products is nestled at refineries along the flood-prone coast.

ENERGY IMPACT: Oil analysts say storm-related supply concerns from Gustav could add $10 to U.S. crude oil prices -- which at recent levels near $115 a barrel are still far short of the record $147.27 set on July 11.

The U.S. Department of Energy has said it is ready to tap the Strategic Petroleum Reserve in the event Gustav causes a severe production disruption. But if refineries are closed due to flooding, they will not be able to convert the emergency crude oil supply to usable products.

NEXT STORM: Looking forward to the next incoming storm, Tropical Storm Hanna, now looming off Florida, could threaten the state's crops of fruits and vegetables if it dumps massive amounts of rain on farmlands. Tropical Storm Fay in August dropped more rain on Florida than any other previous tropical storm, saturating the ground and raising the possibility of serious flooding.

(Reporting by Chris Baltimore; Editing by Mary Milliken and Peter Cooney)