Scientists say adios to la nina

Cynthia O’Carroll/Lynn Chandler
(Phone: 301-614-5563)
Lynn.Chandler.1@gsfc.nasa.gov

RELEASE NO: 00-50

La Nina, the large area of cold water in the Pacific Ocean widely blamed for last
summer’s drought and often related to an increase in the number of hurricanes that make
landfall, appears to be on its last legs. According to the latest spacecraft and ocean
buoy observations, the La Nina has disappeared entirely in the eastern Pacific Ocean and
is rapidly disappearing over the rest of the Pacific.

"The current lack of cold water support below the surface means that this La Nina
will have a difficult time sustaining itself for much longer", according to David
Adamec, a research oceanographer at Goddard Space Flight Center in Greenbelt, Md. "As
expected, the La Nina reached a maximum in intensity during January 2000 and has been
waning ever since."

The spacecraft data have also shown that since March, La Nina’s cold surface water is
being replaced by water that is now 4 degrees Fahrenheit warmer than normal off the coast
of South America. The current longevity of this "warm water patch" is now
beginning to affect the atmosphere by weakening the trade winds there. These weakened
winds are also very unfavorable for the persistence of La Nina conditions.

Should the current trends continue and the winds continue to weaken, there is potential
for processes to be set in motion that will allow the warm water in the western Pacific to
enhance and expand the surface warming that has already taken place in the eastern Pacific
Ocean. Scientists will be carefully monitoring the situation as changes in tropical
Pacific Ocean temperatures ultimately affect weather in many parts of the U.S.

Anomalous behavior of the tropical Pacific Ocean has been affecting weather patterns in
the U.S. for the past three years. During the spring of 1997, warm waters off the coast of
South America associated with the strongest El Nino on record led to changes in the storm
tracks over the Pacific that slammed one storm after another into the west coast causing
wide spread flooding there.

Suddenly during May of 1998, the warm waters of El Nino were replaced by the cold water
phenomenon known as La Nina which has persisted till now. During last year’s La Nina
summer, most of the southern tier of the U.S. experienced drought in part due to the
disruption of the weather patterns. Historically, another consequence of La Nina is an
increase in the number of hurricanes that make landfall in the U.S.   The two
hurricanes that made landfall and caused the disastrous flooding along the North Carolina
coast are consistent with that trend.