Wednesday, September 12, 2007

La Niña On Her Way?

The odds of a busy 2007 hurricane season just went up because the water temperature in the Pacific Ocean just went down. That drop in sea surface temperature marks the likely return of La Niña, and an expected increase in stress levels for residents in Florida and other parts of the United States coastline threatened by hurricanes.

Scientists at the Climate Prediction Center announced that La Niña is on its way. “While we can’t officially call it a La Niña yet, we expect that this pattern will continue to develop during the next three months, meeting the NOAA definition for a La Niña event later this year,” said Mike Halpert, acting deputy director of the Climate Prediction Center in Camp Springs, Md.

La Niña conditions occur when ocean surface temperatures in the central and east-central equatorial Pacific become cooler than average. These changes affect tropical rainfall patterns and atmospheric winds over the Pacific Ocean, which influence the patterns of rainfall and temperatures in many areas worldwide.

“La Niña events sometimes follow on the heels of El Niño conditions,” said Vernon Kousky, research meteorologist at the Climate Prediction Center. “It is a naturally occurring phenomenon that can last up to three years. La Niña episodes tend to develop during March-June, reach peak intensity during December-February, and then weaken during the following March-May”.

While past La Nina’s have been responsible for serious droughts in the western United States, it is La Nina’s influence on hurricanes in the Atlantic Ocean and, in particular, the current hurricane season that has caught the attention of local officials.

“Although other scientific factors affect the frequency of hurricanes, there tends to be a greater-than-normal number of Atlantic hurricanes and fewer-than-normal number of eastern Pacific hurricanes during La Niña events,” said retired NOAA administrator Conrad Lautenbacher.

A 1999 study on La Nina’ influence on Atlantic hurricane activity found that “the odds are significantly higher that the U.S. will experience greater (hurricane) impacts because of a larger number of tropical cyclones and higher intensities for each storm.”

The last La Nina lasted from 1998 to 2000, a period that saw 37 tropical storms and 26 hurricanes in the tropical Atlantic. Among the memorable storms during those years were Hurricane Georges that hit the Florida Keys, Hurricane Floyd that threatened Florida and Hurricane Irene that swept across South Florida.

Dr. William Gray’s team at Colorado State University recently updated their hurricane forecast for the remainder of the season. Gray thinks the next few months will be active forecasting 10 named storms, 6 hurricanes and three major hurricanes.

This latest news regarding the developing la Nina will not sit well with residents in Florida, the northern Gulf Coast states and other locales still recovering from the active hurricane seasons of 2004 and 2005. And, while everyone received a nice break from Mother Nature last year, it appears more and more likely that the 2007 hurricane season will be busy.

All because the water temperature is going down.

Posted at 11:36 AM