NOAA 99R207
Contact: Delores Clark


Guam and the Commonwealth of the Northern Mariana Islands (CNMI) 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 United States, including one in Hawaii last week.

Speaking at the University of Guam, 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 Guam 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, Guam received above normal rainfall during the normally dry period of January through March, and the excess wetness continued through May. The most recent La Niña in the winter of 1995-96 was weak, but the January through March season, and even the first half of 1996, was still wetter than normal in Guam."

Other La Niñas of the recent past have occurred in the winters and the following springs of 1984-85 (weak), 1975-76 (strong), 1973-74 (strong), and 1970-71 (moderate). Most of these winters brought above normal rainfall to Guam and CNMI.

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. The chances are quite good that this region will see above normal rainfall continuing through April. This wetness may bring welcome relief from the dry conditions brought by last year's strong

El Niño. This forecast applies to Guam, CNMI, Republic of the Marshall Islands (especially the higher latitudes), Federated States of Micronesia (but excluding the islands south of Pohnpei), Palau and Hawaii."

Armed with graphic analyses of conditions in the tropical Pacific Ocean, Barnston explained the genesis of El Niño and the opposite climate phenomenon, 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 (but farther away from the equator in the eastern Pacific) tend to experience suppressed rainfall with El Niño and above normal rainfall with La Niña.

The impact on the 1999 typhoon 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. - affiliated 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."

For more information on the Climate Prediction Center and its forecasts, log onto: For more information on Guam climate, log onto: Pacific islands climate data may be found at:

NOTE TO EDITORS: Hurricanes, cyclones, and typhoons are terms that have the same meaning and are used interchangeably. For instance, "Typhoon/Typhoon Season is commonly used in the western Pacific past the International Date Line, but "Hurricane/Hurricane Season" is officially used in Hawaii.