Workers place plywood on the windows of the Royal Sonesta Hotel on Bourbon St. to prepare for Tropical Storm Isaac in New Orleans, Louisiana. - 

There is a hurricane warning in effect from Louisiana to Florida including the city of New Orleans, as tropical storm Isaac gains strength and hurdles toward the gulf coast.

By this time tomorrow, we'll have a better idea of Isaac's impact on land. But it's already having an impact at sea.

Don Briggs is president of the Louisiana Oil and Gas Association and he joins us now from Lafayette, Louisiana. He says the actual damages due to the storm have been limited to wind and rain. The main effect, as far as business goes, is on oil refineries.

"The refineries in Louisiana represent about 25 to 30 percent of gas production in the country," Briggs says. "Should they all shut in, you should expect to see a rise in prices because of supply."

Follow Jeremy Hobson at @jeremyhobson