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LA NIÑA
MAY SOON ARRIVE
NOAA
satellite image for larger view of sea surface temperature anomalies in the
Eastern Pacific Ocean taken Feb. 27, 2007, showing the development of La Niña
conditions.
Feb. 28, 2007 — On the heels of
El Niño, its opposite, La Niña may soon arrive.
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 U.S. 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. “During the winter, usual La Niña impacts
include drier and warmer-than-average conditions over the southern United
States."
“NOAA's ability to detect and
monitor the formation, duration and strength of El Niño and La Niña events is
enhanced by continuous improvements in satellite and buoy observations in the
equatorial Pacific,” Lautenbacher added. “These observing systems include
the TAO/TRITON moored and Argo drift buoys, as well as NOAA's polar orbiting
satellites.”
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 U.S. Spring
Outlook on March 15, and its Atlantic Hurricane Season Outlook in May. Both
outlooks will reflect the most current La Niña forecast.
“While the status of El Niño/La
Niña is of vital importance to our seasonal forecasts, it is but one measure we
use when making actual temperature and precipitation forecasts,” said Kousky.
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