| | |  Editorials | Environmental 
La Niña is Packing a Bigger Punch
 Associated Press
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September 11, 2010
| | Emmanuel Perez, 4, looks at a flooded Dallas street from his family's stalled car. His family waited for help after trying to drive through high water in the aftermath of Tropical Storm Hermine. (Sonya N. Hebert/Dallas Morning News) | |
The climate phenomenon, marked by the cooling of the tropical Pacific Ocean, is strengthening, creating conditions that could mean an even busier hurricane season.
La Nina climate phenomenon is strengthening, increasing the likelihood that an active hurricane season could get even busier.
The update from the National Oceanic and Atmospheric Administration on Thursday comes as residents of Texas and Mexico are cleaning up from the deluge of Tropical Storm Hermine, and as Tropical Storm Igor is drifting in the Atlantic.
La Nina is marked by a cooling of the tropical Pacific Ocean and was reported to be developing a month ago. It strengthened throughout August and appears likely to last at least through early 2011, NOAA's Climate Prediction Center said.
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"La Nina can contribute to increased Atlantic hurricane activity by decreasing the vertical wind shear over the Caribbean Sea and tropical Atlantic Ocean," the center noted.
Wind shear is a sharp difference in wind speed at different levels in the atmosphere. A strong wind shear reduces hurricanes by breaking up their ability to rise into the air, while less shear means they can climb and strengthen.
NOAA has been predicting an above-normal tropical storm season. The forecast issued last month anticipates 14 to 20 named tropical storms. The hurricane season started June 1 and ends Nov. 30, but the peak period runs from August through October.
La Nina's cooling of the tropical Pacific is the opposite of the El Nino event, which is marked by unusually warm tropical water in that region. Each can take place every few years, usually with neutral conditions in between.
Both can affect climate worldwide by changing the direction and strength of winds and altering air pressure and rainfall patterns.
In addition to hurricanes in the Atlantic and Gulf of Mexico, the effect of La Nina can include above-average rainfall or snowfall in the Pacific Northwest and below-average precipitation in the Southwest.
La Nina tends to suppress hurricane activity across the central and eastern tropical North Pacific and increases rainfall in Indonesia.
NOAA said its computer climate models disagree on how strong this La Nina will be, but all concur it will last at least through early 2011. |
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