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Contact: Delores Clark
The Hawaiian Islands can expect a slightly wetter and longer than average winter this year due to the effects of La Niña, said a climate expert with the National Weather Service at a La Niña briefing presented today. Briefings have been held across the country with one set for Guam next week.
Speaking at the Honolulu Forecast Office, Anthony Barnston, a NOAA research meteorologist at the weather service's Climate Prediction Center in Washington, D.C., noted that this year's La Niña will reverse some of the impacts of El Niño, but will not have as great an impact on the global climate as her counterpart.
"During past cases of La Niña, rainfall in Hawaii has tended to be near to above normal. The rainy season has also lasted longer into the spring during La Niña years," said Barnston. "For example, in the winter of 1988-89, when the last strong La Niña occurred, Hawaii received above normal rainfall not only during the normally wet period of January through March, but the excess wetness continued through May at most locations. The most recent La Niña in the winter of 1995-96 was weak, but the January through March season was still slightly wetter than normal in most Hawaiian locations."
Other La Niñas of the recent past have occurred in the winters of 1984-85 (weak), 1975-76 (strong), 1973-74 (strong), and 1970-71 (moderate). Most of these winters brought above normal rainfall to Hawaii as well as the U.S. - affiliated islands farther west.
Barnston added, "The present moderate La Niña is stronger than the 1995-96 event, but not as strong as 1988-89 or the ones in the mid-1970's. Therefore, the chances are quite good that this region will see a generally wet winter with above normal rainfall continuing through at least April. This wetness may bring welcome relief from the dry conditions experienced last winter due to the strong El Niño which dissipated early last summer. This forecast applies to Hawaii, the Marshall Islands, Micronesia, Guam, and Palau."
Armed with graphic analyses of conditions in the tropical Pacific Ocean, Barnston explained the genesis of El Niño and the opposite climate phenomena, La Niña. "When these warm waters retreat to the western Pacific and are replaced by colder waters, you have a La Niña," Barnston said.
These events, which are monitored by a network of buoys and satellites operated by NOAA and the international community, impact the weather throughout the world. For example, India and northern Australia tend to receive a deficient summer monsoon season with El Niño, and plentiful rainfall with La Niña. From December through April, Indonesia and most of the Pacific islands that are more than 8 to 10 degrees latitude away from the equator tend to experience suppressed rainfall with El Niño, and above normal rainfall with La Niña. The Hawaiian islands are included in this category.
The impact on the 1999 hurricane season is more challenging to predict. During La Niña, more cyclones are generated in the western part of the western north Pacific and fewer are generated east of 150°E. This means that for Hawaii and most of the U.S. -affilated islands, including Guam, the odds for a land-falling tropical cyclone decrease. However, islands farther west such as Yap and Koror still have a close to normal chance of a typhoon. By June, scientists should know more about how El Niño-La Niña will influence the 1999 Pacific cyclone season.
The Climate Prediction Center conducts statistical research and uses computer models to predict future climate trends. "Hurricanes and droughts will still occur regardless of the impact of El Niños and La Niñas," Barnston concluded. "While our research attempts to get a handle on the frequency and severity of weather events, the bottom line remains: people should be aware of severe weather and be prepared to take steps to protect life and property."
NOTE TO EDITORS: Hurricanes, cyclones, and typhoons are terms that have the same meaning and are used interchangeably. However, while "Hurricane/Hurricane Season" is officially used in Hawaii, "Typhoon/Typhoon Season" is commonly used in the Pacific, past the International Date Line.