Signs of the return of La Niña may indicate an active Atlantic hurricane season

According to NOAA the El Niño conditions which have been in place recently may be replaced by opposite, La Niña, conditions.

In a weekly update, scientists at the NOAA Climate Prediction Center noted that as the 2006-2007 El Niño faded, surface and subsurface ocean temperatures have rapidly decreased. Recently, cooler-than-normal water temperatures have developed at the surface in the east-central equatorial Pacific, indicating a possible transition to La Niña conditions.

Typically, during the US spring and summer months, La Niña conditions do not significantly impact overall inland temperature and precipitation patterns, however, La Niña episodes often do have an effect on Atlantic and Pacific hurricane activity.

“Although other scientific factors affect the frequency of hurricanes, there tends to be a greater-than-normal number of Atlantic hurricanes and fewer-than-normal number of eastern Pacific hurricanes during La Niña events,” said retired Navy Vice Adm. Conrad C. Lautenbacher, Ph.D., under secretary of commerce for oceans and atmosphere and NOAA administrator.

La Niña conditions occur when ocean surface temperatures in the central and east-central equatorial Pacific become cooler than normal. These changes affect tropical rainfall patterns and atmospheric winds over the Pacific Ocean, which influence the patterns of rainfall and temperatures in many areas worldwide.

“La Niña events sometimes follow on the heels of El Niño conditions,” said Vernon Kousky, research meteorologist at the NOAA Climate Prediction Center. “It is a naturally occurring phenomenon that can last up to three years. La Niña episodes tend to develop during March-June, reach peak intensity during December-February, and then weaken during the following March-May.

“The last lengthy La Niña event was 1998-2001, which contributed to serious drought conditions in many sections of the western United States,” said Douglas Lecomte, drought specialist at the NOAA Climate Prediction Center.

NOAA will issue the US Spring Outlook on March 15, and its Atlantic Hurricane Season Outlook in May. Both outlooks will reflect the most current La Niña forecast.

•Date: 1st March 2007 • Region: US •Type: Article •Topic: Warnings
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