According to the latest statement by the Climate Prediction Center, the current El Nino is expected to strengthen and last through the 2009-2010 winter (El Nino/Southern Oscillation (ENSO) Diagnostic Discussion).
Atlantic Basin Hurricane Season
The effects of the El Nino on northern hemisphere weather during the summer and fall is limited, but it does typically reduce the number of hurricanes in the Atlantic Basin (which includes the Gulf of Mexico). The season is obviously off to a slow start, with no named storms yet; however, the peak of the season (roughly August 15-October 1) has yet to arrive. The presence of the El Nino means that the number of storms developing in the deep tropics will likely be lower; however, there is always the potential for development closer to the coast of the U.S., so the presence of an El Nino does not mean that devastating storms cannot occur.
I recently spoke about the potential effects of the El Nino on the winter in the United States (El Nino Is Back In Town), at least the effects of a strong El Nino. A weak or even moderate El Nino will not have such pronounced impact on the weather.
I expect that long-range forecasts for winter 2009-2010 will largely mirror the influences of a strong el nino, especially in light of the recent statements by the CPC; however, the first long-range forecast I’ve seen (from AccuWeather) is based on a weakening El Nino during the winter, not a strong El Nino. The result is the forecast of Snowy, Cold Winter on the Way for the Northeast and Mid-Atlantic regions.