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EL NIÑO
GAINS STRENGTH
Dec. 7, 2006 — The latest El
Niño/Southern Oscillation Diagnostic Discussion, produced by scientists at the
NOAA Climate Prediction Center, indicates El Niño conditions are now evident in
the tropical Pacific and should intensify during the next one to three months.
However, this episode is expected to be much weaker than the very strong
1997-1998 El Niño event.
“Evolving current conditions in
the equatorial Pacific are likely to cause a substantial increase in sea surface
temperature along the west coast of South America in late December 2006 and
January 2007,” said Vernon Kousky, Ph.D., NOAA’s lead El Niño forecaster.
“At about the same time, rainfall is expected to increase over the warm waters
in the central equatorial Pacific, thus setting the stage for typical El Niño
effects over the U.S. during January through March 2007,” he added
El Niño events influence the
predominate position and strength of the jet stream over the Pacific Ocean,
which in turn affect winter precipitation and temperature patterns across the
country. During El Niño events, the jet stream is stronger than normal across
the southern U.S. As a result, increased storminess and wetter-than-average
conditions occur across the southern tier of the U.S. from central and southern
California across the Southwest to Texas and across the Gulf Coast to Florida
and the Southeast. Meanwhile, drier-than-average conditions are experienced in
the Ohio and Tennessee Valleys, and in the northern Rockies.
“NOAA’s investment in climate
models is paying off,” said Jim Laver, director of the NOAA Climate Prediction
Center. Statistical and coupled model forecasts, including the NOAA National
Centers for Environmental Prediction Climate Forecast System, show El Niño
conditions peaking during the northern hemisphere winter (December 2006 through
February 2007) and then weakening during the northern hemisphere spring (March
through May 2007). “This event may be with us for a while, and we will be
closely monitoring how the atmosphere reacts,” he said.
The term El Niño refers to the
large-scale ocean-atmosphere climate phenomenon linked to a periodic warming in
sea surface temperatures across the central and east-central equatorial Pacific
(between approximately the date line and the South America coast). El Niño
represents the warm phase of the El Niño/Southern Oscillation, or ENSO, cycle,
and is sometimes referred to as a Pacific warm episode. Originally, the term
referred to an annual warming of sea surface temperatures along the west coast
of tropical South America. Typically, El Niño episodes occur every 3 to 5
years. However, in the historical record this interval has varied from 2 to 7
years.
The next El Niño/Southern
Oscillation Diagnostic Discussion will be published (via the Internet) on
January 11, 2007.
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