The last time El Niño came around, it wreaked havoc on U.S. weather patterns. Some areas of the country saw extreme drought, others saw above normal rainfall. And then there were the temperatures – above normal in the north, below normal in the south. University of Kentucky College of Agriculture Meteorologist Tom Priddy said El Niño is brewing again in the Pacific and could affect Kentucky by December.

“Current weather models indicate the atmosphere-ocean teleconnection, called El Niño, along the Pacific equator, is starting to boil into a stew again,” he said. “This is similar to 1983, 1987, and 1997/98. For Kentucky it could mean a very different weather pattern later this fall through next winter, including cooler and wetter conditions.”

El Niño occurs every four or five years and always begins with the warming of Pacific waters near the equator. Priddy describes it as a teleconnection because it affects weather in other parts of the world. He said warmer-than-normal sea surface and subsurface temperatures occurred in the equatorial Pacific during February and March 2002.

“The warming of surface and subsurface waters along the South American coast was a result of the arrival of the oceanic Kelvin wave that has been propagating eastward from the central equatorial Pacific since mid-December,” he said. “These conditions are often observed in the early stages of El Niño.”

Priddy does admit that several atmospheric indices indicate El Niño has not yet developed to a point that guarantees sustained growth of the event, however those indices often are inconsistent in the early stages of El Niño and they develop El Niño characteristics as the event evolves.

“Even though those indices don’t support a pattern of sustained growth yet, enhanced rainfall has already been observed over the tropical west-central Pacific from Papua, New Guinea, eastward to the date line (180̊W) since the beginning of 2002,” Priddy said. “Enhanced rainfall also developed in late February over the warmer-than-normal waters between the west coast of South America and the Galapagos Islands.”

Priddy said those features reflect the warming in the sea surface temperatures, and are possibly the first atmospheric effects of a developing El Niño.

The latest statistical and coupled model predictions show a spread from slightly cooler-than-normal conditions to moderate warm-episode conditions during the remainder of 2002. The coupled models and some statistical techniques that incorporate subsurface oceanic conditions indicate a slow evolution to weak or moderate warm-episode (El Niño) conditions during the next several months.

Other techniques indicate that conditions will remain near normal or even return to slightly colder than normal for the remainder of 2002. The recent evolution in oceanic conditions supports the forecasts of a continued evolution toward El Niño, Priddy continued.

So, it’s really too early to tell just what impact, if any, El Niño will have on Kentucky in the upcoming year. If the waters in the Pacific continue to warm, the Commonwealth could be in for a unique dance with the weather.