The La Nina climate phenomenon is strengthening, increasing the likelihood an active hurricane season could get even busier.

The update from the National Oceanic and Atmospheric Administration on Thursday comes as residents of Texas are cleaning up from the deluge of Tropical Storm Hermine, and 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 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.  [ MyWay News ]