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Weather shift may increase hurricanes

Flooding from Tropical Storm Hermine, which killed three people in Texas, submerged a truck. Flooding from Tropical Storm Hermine, which killed three people in Texas, submerged a truck. (Rusty Schramm/The Temple Daily Telegram via Ap)
Associated Press / September 10, 2010

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WASHINGTON — The 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 yesterday comes as residents of Texas 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 next year, NOAA’s Climate Prediction Service said.

“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.

The NOAA had said last month it anticipates 14 to 20 named tropical storms, an above-normal season.

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 phase 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.