NOAA 99-R526
Contact: Jana Goldman


Atlantic hurricanes making landfall create much more damage in La Niña years costing millions of dollars to U.S. coastal communities, according to National Oceanic and Atmospheric Administration and the National Center for Atmospheric Research.

In their article "La Niña, El Niño, and Atlantic Hurricane Damages in the United States," published in the October Bulletin of the American Meteorological Society, Roger Pielke Jr., of the National Center for Atmospheric Research, and Chris Landsea, of the National Oceanic and Atmospheric Administration, compare damage caused by landfall hurricanes during the 1900s (normalized to 1997 dollars) to the number of storms each year and the presence of an El Niño or La Niña.

"We found that in terms of median U.S. cost of damage from hurricanes, 20 times more damage costs occur in La Niña years versus El Niño years," says Landsea, a research meterologist at NOAA's Atlantic Oceanographic and Meteorological Laboratory in Miami, Fla. "The current La Niña, which began in mid-1998 and is ongoing, typifies the damages that can happen in La Niña events, with Hurricanes Bonnie, Earl and Georges last year and Hurricanes Bret, Dennis, and Floyd (so far) this year. The 1998 and 1999 total will likely be more than $7 billion in damages from those hurricanes. These busy years contrast with the last El Niño event in 1997, which produced only $100 million in U.S. damages from Hurricane Danny."

One major conclusion is that not only are there more storms in La Niña years, these storms are stronger, resulting in more damage from wind, storm surge, and rain-related flooding. In terms of U.S. dollars, there is a 77 percent chance that more than $1 billion of hurricane damage will occur in a La Niña year, and a 36 percent chance that more than $5 billion in damage will occur. These probabilities are much greater than the 32 percent and 14 percent chances, respectively, in El Niño years.

"The state of the El Niño-Southern Oscillation has historically proven to be a statistically significant indicator of U.S. hurricane damage, with annual damages in La Niña years totaling many times those during an El Niño event," says Pielke "In addition, damages from individual storms in La Niña years are, on average, twice the cost of damages in El Niño years. For decision makers who can manage their risk, in disciplines like insurance and finance, this information is of large potential value. For the typical coastal resident, however, improved preparation makes sense in any year, as a powerful storm can strike in any season."

La Niña refers to cooler-than-average sea-surface temperatures across the eastern tropical Pacific Ocean. El Niño is an abnormal warming of the ocean temperatures across the eastern tropical Pacific Ocean. Both phenomena bring important consequences for weather around the globe.

These seasonal forecasts help resource and emergency managers prepare for the likelihood of more frequent and stronger hurricanes in La Niña years. However, El Niño and neutral years do not mean no hurricanes will make landfall, and one hurricane can have large impacts. Hurricane Andrew is the most recent example of this phenomenon, a neutral-year storm that became one of the costliest natural disasters in U.S. history, with estimates of $30 billion in damage.

"What this means for decision makers is that the absence of La Niña should not lead to complacency about hurricane impacts," Landsea says.

Scientists stress that El Niño and La Niña are not the only climate factors related to relative levels of hurricane damage. Considerable variation in hurricane damage is evident in neutral years as well. Landsea and Pielke noted that this study revealed only one of the recurring cycles associated with hurricanes. To understand and predict other elements, there is an ongoing body of research calculating the interannual variability of hurricane seasons, track and intensity forecasts of individual storms, and economic impacts, within NOAA and other organizations.

NOAA's mission is to predict and describe changes in the Earth's environment and to conserve and manage wisely the nation's coastal and marine resources.