La Nina conditions are developing in the Pacific Ocean, and that cooling of waters generally brings a more active Atlantic hurricane season, the National Oceanic and Atmospheric Administration said Thursday.

"While we can't officially call it a La Nina yet, we expect that this pattern will continue to develop during the next three months, meeting the NOAA definition for a La Nina event later this year," said Mike Halpert, acting deputy director of the Climate Prediction Center in Camp Springs, Md.

La Nina would likely extend the drought in the U.S. Southwest this fall and create wetter than normal conditions in the Pacific Northwest, experts said.

The conditions also reinforce government and university researchers' forecasts for an above normal Atlantic hurricane season.

So far, there have been five named Atlantic storms this season and two hurricanes. Both hurricanes, Dean and Felix, reached top-scale Category 5 strength before hitting Central America, an unprecedented event in a single year since record keeping began.

Felix slammed Nicaragua on Tuesday with catastrophic 160 mph sustained winds and a storm surge estimated at 18 feet above normal tides. Rescuers on Thursday raised the storm's death toll to more than 40 with scores of others missing.

Hurricane forecaster William Gray, at Colorado State University, downgraded his forecast for the 2007 season slightly this week, but he still predicted above-average activity for the rest of the season through the end of November, with five more hurricanes, two of them major with sustained winds of at least 111 mph.

La Nina is the counterpart to El Nino, a warming of Pacific waters near the equator. Both ocean conditions are hard to predict long-term and do not follow regular patterns.