The Climate Prediction Center (CDC) is predicting a moderate to strong El Nino for the winter of 2009/2010. CDC defines El Nino as:
A one-month positive sea surface temperature anomaly of 0.5C or greater is observed in the Niño-3.4 region of the equatorial Pacific Ocean (5ºN-5ºS, 120ºW-170ºW) and an expectation that the 3-month Oceanic Niño Index (ONI) threshold will be met AND
An atmospheric response typically associated with El Niño is observed over the equatorial Pacific Ocean.
The potential impacts of El Nino on US weather are: A suppressed Atlantic hurricane season, suppressed tornado activity in the Southern Plains with increased tornado chances in the Ohio River Valley and the Deep South, warmer than normal winter-time temperatures for the northern US, and wetter than normal conditions for California and the southern US.
Matt
www.WxForecastNow.com