El Nino to La Nina pattern could prompt drastic weather change

By Aimee Nielson

 

LEXINGTON, Ky, (Mar 11, 2010)

In 1998, Kentucky experienced a very wet spring due to a strong El Nino weather pattern. Then El Nino conditions in the equatorial Pacific turned to La Nina – the cooling of water in the Pacific Ocean – that led the Bluegrass State into a summer drought. Some weather models are indicating that history may repeat itself in 2010.

"I'm not forecasting a summer drought," said University of Kentucky Agricultural Meteorologist Tom Priddy. "I am saying that some weather models are indicating that the current strong El Nino pattern will quickly turn to La Nina, and it will definitely affect our weather in Kentucky and the Ohio Valley."

Priddy said current models indicate that El Nino will die out this spring and sea surface temperatures in the equatorial Pacific will become near normal, which would end the very active weather that brought the commonwealth such a cold, snowy winter. Conditions would return Kentucky and the Ohio Valley to a more normal spring scenario, which could be very wet.

"1998 was also a very active weather year for this state and the entire United States, in fact," Priddy said. "After a strong El Nino for more than a year, it ended in April and a strong La Nina developed in May. So after an unusually wet spring through June of that year, Kentucky got very dry that summer."

That year was the worst case scenario for the state with regard to agricultural production since the spring was too wet to get crops established, and then the summer was too dry to get any yield for harvest, Priddy explained.

"Let me be clear," he added. "No one is predicting a drought this summer, but if La Nina returns after this El Nino, Kentucky will not experience optimum growing conditions."

One additional concern with La Nina potentially taking over is more Atlantic hurricanes.

"During La Niña more hurricanes form in the deep Tropics from African easterly waves," he said. "These systems have a much greater likelihood of becoming major hurricanes, and of eventually threatening the U.S. and Caribbean Islands."

Priddy said there also tends to be considerable month-to-month variations in temperature, rainfall and storminess across central North America during a spring La Nina.

Some highlights of the El Nino effect during the 2009-2010 winter were below normal temperatures, resulting in the 14^th coldest Kentucky February on record. Priddy reported some areas of the state were even cold enough to go into the record books in the top 10 coldest Februarys. Interestingly, some parts of the state were pretty dry, while other areas such as Louisville, Lexington and Jackson were around 8 inches above normal snowfall.

Now, Priddy said, it's just a waiting game in the equatorial Pacific to see what spring and summer will bring.