Forecasters predict La Nina will last at least until June

Sea Technology, Mar 1999

Record snowfall and sub-zero temperatures in the Midwest and Northeast, heavy rains in the Northwest, and conditions that have fueled tornado outbreaks in the South resemble the characteristics of La Nina predicted last September by meteorologist with the Commerce Department's NOAA. The latest forecast from NOAA's National Weather Service reveals La Nina will linger through June, if not longer.

La Nina, the climactic opposite of El Nino, is defined as cooler than normal sea-surface temperatures in the tropical Pacific Ocean that impact global weather patterns. Conditions for this cold episode strengthened throughout the tropical Pacific in December, as sea surface temperatures continued to drop. A month later, many Americans are feeling the effects.

"The conditions we're seeing that are generating weather extremes this winter are largely consistent with La Nina," said Ed O'Lenic, a forecaster at the NWS' Climate Prediction Center. "Everyone should be prepared because extreme weather may reoccur this cold season," he added.

Scientists at NOAA's Storm Prediction Center, the national center for severe weather forecasting, report a preliminary count of 101 tornadoes since the new year, breaking the national record for the most tornadoes ever recorded during the month of January. The previous high total was 52 in January 1975.

Currently, a strengthening La Nina has influenced weather patterns that sent Alaskan temperatures dipping to -74oF and wind chills to -90oF in late January and early February, and brought flooding and heavy snow to the West, warmth to the East, and extreme weather from South America to Asia, according to NOAA scientists.

In May 1998, a rapid cooling of the near equatorial waters in the central Pacific signaled the end of the 1997/98 El Nino and the beginnings of a La Nina. La Nina features colder-than-normal sea surface temperatures in the tropical Pacific Ocean. Many forecast models indicated this transition and that the La Nina would continue to develop. Now, six months later, scientists at the NWS's Climate Prediction Center, say that the event has grown into one of the strongest La Nina episodes of the past 50 years.

"This La Nina provides the physical link between many of the unusual weather patterns seen recently in farflung parts of the globe," said John Janowiak, a NOAA scientist. "While parts of Alaska have experienced severe cold, most of the lower 48 states, especially those in the southern tier, have enjoyed record breaking warm temperatures."

The global La Nina impacts include heavy rains, severe storms, and flooding in southern Africa, drought in Kenya and Tanzania, flooding in the Philippines and Indonesia, and abnormal wetness in northern South America. The same regions suffered the opposite impacts during the 1997/98 El Nino. /st/