The severity of hurricane seasons can be predicted by studying the influence of the El Niño weather pattern, concludes a study by Robert M. Wilson, a research scientist at NASA's Marshall Space Flight Center in Huntsville, Ala.
The study also determined that a consequence of El Niño is less hurricane development in the Atlantic Ocean than when El Niño is not present.
A statistical analysis by Wilson of hurricanes that developed in the Atlantic Ocean, Gulf of Mexico and Caribbean Sea between 1950 and 1998 found that when El Niño was present, the number of intense hurricanes in a season has never risen above three. When El Niño was not present, the number of intense hurricanes in a season rose to as high as seven.
On average, El Niño-related seasons experience about one intense hurricane, the study found, while non-El Niño-related seasons experience about three. In the last 50 years, 14 out of 15 non-El Niño-related seasons had two or more hurricanes.
Wilson's findings will be published in an upcoming issue of the Geophysical Research Letters, a journal of the American Geophysical Union.
"My goal with this research was to show it is quite simple to predict the severity of a hurricane season," Wilson said. "All you need to know is that you are under the influence of an El Niño.
"I anticipate that 1999 will be a busy hurricane season, because we're in a non-El Niño-related year. The ocean temperatures are there. And the right winds are occurring," Wilson said.
"El Niño is a natural part of the climate system, not a beast in and of itself," he said. "It is an interaction between the ocean and the atmosphere that has global consequences. One of the consequences of El Niño is less hurricane development.
"By knowing that intense storms are likely to occur, coastal areas can prepare," Wilson said. "We need to be aware that we have been in an era, from the mid-1960s to the early 1990s, when we have had little hurricane activity. During that time more and more people have moved to coastal areas, so there is a generation that has been lulled into a false sense of security because they are not familiar with the destructive power of hurricanes. Hopefully, this research can act as a warning."
The name El Niño, Spanish for "boy Christ child," originally was used by local fishermen to describe a warming of the Pacific Ocean off Peru and Ecuador. The warming occurs annually, but the fishermen noticed in some years it intensified around Christmas, creating unusual storms and the destruction of marine life in the region.
El Niño events occur about every three to seven years. Just as a clock pendulum swings between two extremes, ocean conditions vary between El Niño (warm water events), La Niña (cold water events), and interlude conditions. Scientists refer to this weather pattern as the "El Niño-Southern Oscillation."
The hurricane season begins June 1, peaks around September 10 and ends November 30, although the bulk of major hurricanes occurs between mid-August and mid-October of each year.
Note to Editors / News Directors: For interviews with Robert Wilson or other information to support this release, media representatives may contact Steve Roy of the Marshall Media Relations Department at (256) 544-0034. For an electronic version of this release, digital images or more information, visit Marshall's News Center on the Web at: http://www.msfc.nasa.gov/news