Hurricane Katrina weakened slightly overnight to a Category Four storm, but its effects were felt from New Orleans to Mobile to Pensacola Monday morning.

Katrina made landfall at about 6:10 a.m. Monday east of Grand Isle in the Louisiana town of Buras with 145-mile-an-hour winds and the potential of a 20-foot storm surge.

Transformers exploded in Mobile, lighting up the pre-dawn sky. As much as three feet of water accumulated in downtown Mobile as the storm moved inland.

An oil tanker ripped free of its moorings in the Mobile River as the storm roared in.

In Biloxi, Miss. an estimated 1,000 people took shelter in schools as Katrina hammered the area.

The Mississippi coast appeared to be bearing the brunt of the storm Monday morning.

High winds blew out windows in New Orleans, where streets quickly filled with debris.

The Louisiana Superdome, where thousands had gathered to wait out the storm, sprung a leak as the storm ripped two holes in the roof.

The biggest fear remains the impact of the storm surge and flooding on New Orleans, which is below sea level and in a sort of a bowl, dependent on a network of levees, canals and pumps to stay dry.

If the levees are breached, parts of the city could end up under as much as 10 or 20 feet of water, experts say.

The hurricane turned slightly to the east as it made landfall Monday, however, offering some hope that the worst of the storm might miss the vulnerable city.

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