January 23, 2010

Fewer But Stronger Atlantic Hurricane Forecast

The strongest Atlantic hurricanes may almost double in frequency by the end of the century as the planet warms, according to a report published Friday in the journal Science.

The new study used the most extensive computer modeling of storm activity to date. 

The results indicate that while the total number of Atlantic storms could fall nearly 30 percent over the next 80 years, the number of Category 4 and 5 hurricanes, the strongest and most destructive storms, could rise by 81 percent.

The end result may be a 30 percent increase in property damage, said study co-author Tom Knutson, a climate scientist at the National Oceanic and Atmospheric Administration (NOAA), in an interview with Bloomberg.

"There will be fewer storms, more of these more intense storms, and it works out to some increase in damage potential," he said, adding that the 81 percent increase equates to about a doubling over the next century.

The area northeast of Cuba and to the east of Florida may see the biggest spike in incidence and intensity of hurricanes, the study found.

The research could have implications for the multibillion-dollar tourism industries of Florida and the Bahamas, and for oil operations in the Gulf of Mexico, Bloomberg said.

Storms rated Category 4 or 5 on the five-step Saffir-Simpson scale have speeds of at least 131 mph, and are projected to increase in frequency in the coming decades. By comparison, Hurricane Katrina, which wiped out New Orleans in 2005 causing more than $80 billion in damages and killing 1,833 people, was only a Category 3 storm when it made landfall.

In conducting their study, researchers assumed an average rise in sea-surface temperature of the tropics of 1.7 degrees Celsius due to global warming over the next 80 years, Knutson said. Such warmer waters are more likely to result in hurricane formation.

The total number of hurricanes would drop, Knutson said, because conditions in the area where the storms typically begin are projected to be less favorable to cyclone formation, Knutson said.

However, those that do form and move out of the region will find conditions more likely to foster added intensity, so that the strongest hurricanes will become more frequent, he explained.

The most significant increase in stronger storms was detected north of the 20 degrees north line of latitude that runs south of Cuba through the Yucatan Peninsula in Mexico, Morris Bender of NOAA, lead author of the study, told Bloomberg.

According to the study, the area east of Florida, including the Bahamas, could be hit with three more Category 4 and 5 storms per decade.

The increase in frequency of stronger storms could affect companies such as Blackstone Group LP's Hilton Hotels Corp. and cruise operator Carnival Corp., Bloomberg said. 

Other industries would be impacted as well, including oil platforms and facilities in the Gulf of Mexico operated by companies such as BP, Exxon Mobil and Chevron.  The data from the study suggests a change in hurricane frequency from an additional one stronger storm per decade to a decrease of one.

However, researchers said the percentage trend across the entire Atlantic basin is a better metric to consider, given the complexity of regional modeling.

"Because of the inherent uncertainties of the climate looking into the future, we're more comfortable talking about the Atlantic as a whole," Bender said.


Image Caption: Hurricane Katrina was the costliest and one of the five deadliest hurricanes in the history of the United States, costing over 1800 lives and $81.2 billion USD. Courtesy Jeff Schmaltz, MODIS Rapid Response Team, NASA/GSFC


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