Hurricane Gustav is menacing Cuba with winds of nearly 150 mph as it continues its threatening march toward the Gulf Coast. The National Hurricane Center says Gustav is an extremely dangerous Category Four storm. It could mushroom into the worst category, Category Five, as it heads into the Gulf. As of 4 p.m. Central time, a hurricane watch was in effect for the northern Gulf Coast from east of High Island, Texas, eastward to the Alabama-Florida border, including New Orleans and Lake Pontchartrain. That's the area devastated by Hurricane Katrina three years ago. Massive evacuations are under way as a precaution against a repeat of that disaster. Gustav's eye is about 80 miles south-southwest of Havana. People are being told not to go outside, with winds increasing rapidly as the eyewall passes. The hurricane should cross western Cuba tonight and emerge over the southern Gulf of Mexico early tomorrow, and reach the northern Gulf Monday.