With the official start of Atlantic hurricane season less than a week away, forecasters anticipate a year of powerful storms akin to 2005, when Hurricanes Katrina and Rita battered the Gulf Coast. Both of those storms generated powerful winds and storm surges -- and with oil from the BP disaster continuing to spread through the Gulf, fears are growing that a landfalling hurricane could carry pollution far inland.
Scientists at Colorado State University, home to one of the nation's top hurricane forecasting programs, expect 15 named storms this season, including four major hurricanes, defined as Category 3 or more. The National Oceanic and Atmospheric Administration takes it further, forecasting 14 to 23 named storms this year and three to seven major hurricanes. Seasonal forecasts are based on a number of global factors, ranging from sea surface temperatures in the Caribbean to the condition of El Niño in the Pacific.
The oil slick resulting from the Deepwater Horizon drilling platform explosion now covers close to 29,000 square miles of sea surface (the size of around 860 Manhattan islands), according to independent experts. It's located just off the northeastern coastline of the Gulf of Mexico, where Katrina killed 1,500 people and caused $80 billion in damage in 2005, making it the costliest natural disaster in U.S. history.
An oil slick on a smooth, happy sea might theoretically inhibit moisture from rising off the ocean's surface, shutting down the energy source for hurricanes and helping weaken them before landfall. But Philip Klotzbach, an atmospheric scientist at Colorado State, says that a storm's heavy winds would mix up the water and break up the surface patches of oil, leaving plenty of seawater exposed to evaporation.
"This is totally uncharted territory," says Christopher Davis, a senior scientist at the National Center for Atmospheric Research, "but I would have to say [the oil slick] is unlikely to have an effect on hurricane formation."
The most powerful storms develop over the Atlantic Ocean, where they have plenty of time to feast on evaporating moisture and gather force. And a storm passing over the Gulf oil slick would be moving so fast that even if the slick diminishes its power, the effect would be short-lived.
The strength of a hurricane is defined by its wind speed, but often the powerful waves they plow before them -- known as the storm surge -- do the worst damage, says meteorologist Ken Graham, who runs the National Weather Service office in New Orleans. Hurricane Katrina brought surges of more than 30 feet to the Mississippi coast, causing flooding many miles inland. The waters from Hurricane Rita, which hit later that season, surged as high as 15 feet in some areas, according to the National Weather Service. They traveled as far as 25 miles inland.
Even without millions of gallons of oil floating in the sea, surges can cause severe pollution problems on land. Katrina's surge caused more than 200 spills of petroleum, hazardous chemicals, and natural gas from the refineries, factories, and other industrial facilities that line the Gulf Coast.
The Gulf oil slick compounds these risks. But there is little if any research on the interactions of hurricanes and offshore oil spills, so it's hard to estimate the potential for a strong surge to carry the oil slick inland, Klotzbach says. "It depends how concentrated the oil is, how much oil is left when the storm comes in, how big the storm is."
The Atlantic hurricane season starts on June 1 and runs through November 30. It typically peaks between August and October, although the Gulf often gets a larger share for early-season storms than the rest of the Atlantic basin.
