Isaac to Drench Florida on Way to Northern Gulf Coast

Tropical Storm Isaac may drop as much as 10 inches (25 centimeters) of rain on Florida as it moves into the Gulf of Mexico on a course that is expected to take the system through oil and gas fields and then onto land near the Louisiana-Mississippi line.

Isaac passed just south of Key West, Florida, with winds of 60 miles (97 kilometers) per hour as of 5 p.m. New York time, the National Hurricane Center said in an advisory. An earlier forecast that called for Isaac to become a hurricane when it struck the Keys didn’t materialize.

The center said there is a chance the storm may grow to at least a Category 2 hurricane with winds of 100 mph before landfall on Aug. 29.

“Even though I am still nervous about it, I think it is too big and that will preclude any rapid intensification,” said Jim Rouiller, senior energy meteorologist at Planalytics Inc. in Berwyn, Pennsylvania. “No hurricane is a piece of cake, though. Every one of these storms represents a different set of problems.”

Isaac’s threat forced the Republican Party to delay its convention in Tampa. Delegates will convene tomorrow as scheduled and then recess until the next day to be safe, said Reince Priebus, the Republican National Committee chairman.

Emergencies Declared

Louisiana Governor Bobby Jindal, citing the uncertainty of the storm track, followed Florida Governor Rick Scott in declaring a state of emergency.

Isaac is expected to drop 4 to 7 inches of rain across southern Florida, with some areas receiving as much as 10 inches, according to the hurricane center. Almost 470 flights at were canceled at Miami International Airport, according to FlightAware, a Houston-based airline tracking company.

About 24 percent of U.S. oil production and 8.2 percent of natural-gas output from the Gulf is shut because of Isaac, the Bureau of Safety and Environmental Enforcement said today. The Gulf is home to 23 percent of U.S. crude production, 7 percent of natural gas output and 44 percent of refining capacity.

Oil and gas companies including Anadarko Petroleum Corp. (APC), BP Plc (BP/), and Chevron Corp. pulled crews from offshore platforms.

The storm’s track has been drifting west from earlier forecasts that had it hugging Florida’s west coast and making landfall in the state’s Panhandle. The official track now calls for Isaac to land near Gulfport, Mississippi, close to where Hurricane Katrina made landfall in 2005.

Predicting Path

Computer forecast models disagree on the storm’s exact path.

“Because of the wide model spread there continues to be greater than usual track forecast uncertainty,” Richard Pasch, a senior hurricane specialist with the center, wrote in a forecast analysis.

A hurricane watch now extends from Indian Pass, Florida, to east of Morgan City, Louisiana, including New Orleans, which was devastated by Katrina in 2005. All hurricane warnings for southern Florida have been changed to tropical storm bulletins.

While some of the models suggest Isaac may gain a lot of strength crossing the warm waters of the Gulf, larger storms often need more time to intensify, Rouiller said. He predicts Isaac won’t have enough time.

Rouiller said computer models disagree on whether a low- pressure trough over the U.S. will pull the storm north. Some models say the trough will act like a conveyor belt and move Isaac into the coastline nearer Florida’s Panhandle, while others say “Isaac has missed his ride,” Rouiller said. Those models take Isaac closer to New Orleans.

Forecasting the track of a hurricane depends on predicting what the upper-level winds in the atmosphere will be doing, said Dan Pydynowski, a senior meteorologist with AccuWeather Inc. in State College, Pennsylvania. Hurricanes don’t move under their own power, they are pulled and pushed by other weather patterns.

“The wind higher-up is what is really steering these storms,” he said.

To contact the reporters on this story: Brian K. Sullivan in Boston at bsullivan10@bloomberg.net; Asjylyn Loder in New York at aloder@bloomberg.net

To contact the editor responsible for this story: Dan Stets at dstets@bloomberg.net.

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