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La Nina conditions likely to prevail
October 20, 1999
A repeat of last year's mild La Nina conditions -- with a
stormy winter in the Pacific Northwest and a dry winter in the
southwestern United States -- will be the likely outcome of sea-
surface heights observed by NASA's TOPEX/Poseidon satellite,
scientists say.
TOPEX/Poseidon has detected lower than normal sea-surface
heights in the eastern North Pacific and unusually high sea-
surface heights in the western and mid-latitude Pacific. The
height of the sea surface over a given area is an indicator of
ocean temperature and other factors that influence climate.
The latest measurements, taken during a 10-day data cycle
October 5-15, are available at http://www.jpl.nasa.gov/elnino .
Sea-surface height is shown relative to normal (green) and
reveals cooler water (blue and purple) measuring about 14
centimeters (6 inches) lower in the eastern North Pacific, from
the Gulf of Alaska to central Alaska, and along the equator. The
cooling trend sets the stage for another La Nina this winter.
A mirror image of that oceanic profile prevails in the
western and mid-latitude Pacific Ocean, where higher than normal
sea-surface heights (red and white) are currently about 20
centimeters or 8 inches. Unusually warm temperatures (shown in
red and white) have persisted and topped last year's
temperatures, said Dr. William Patzert, an oceanographer at
NASA's Jet Propulsion Laboratory, Pasadena, CA.
"These unbalanced conditions will undoubtedly exert a very
strong influence on climate over North America this fall and
winter," Patzert said. "Our profile of high sea-surface heights
and warm temperatures in the western Pacific Ocean contrasts with
low sea-surface heights and cool conditions in the eastern and
equatorial Pacific. Those conditions will have a powerful impact
on the weather system delivering jet streams out of the North
Pacific."
Conditions are ripe for a stormy, wet winter in the Pacific
Northwest and a dry, relatively rainless winter in Southern
California and the Southwest, the data show. "Clearly, these
unusual conditions, which have persisted for 2 1/2 years, will
not be returning to normal any time soon," Patzert said. "This
climate imbalance is big and we're definitely going through a
decade of wild climatic behavior. But when we look back at the
climate record over the past century, we've seen behavior like
this before."
The TOPEX/Poseidon satellite's measurements have provided
scientists with a detailed view of the 1997-1999 El Nino/La Nina
climate pattern by measuring the changing sea-surface height with
unprecedented precision.
For more information, please visit the TOPEX/Poseidon project
web page at
http://topex-www.jpl.nasa.gov/
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