May 10, 2000 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.
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