El Niño update

El Niño expected to strengthen and last through the Northern Hemisphere winter 2009-2010
October 22, 2009

El Niño update 

A weak El Niño continued during September 2009, as sea surface temperature (SST) anomalies remained nearly unchanged across much of the equatorial Pacific Ocean.

A majority of the model forecasts by the U.S. National Oceanic and Atmospheric Administration (NOAA) suggest that El Niño will reach at least moderate strength during the Northern Hemisphere fall (3-month Niño-3.4 SST index of +1.0°C or greater).  Many model forecasts even suggest a strong El Niño (3-month Niño-3.4 SST index in excess of +1.5°C) during the fall and winter, but in recent months some models, including the NCEP CFS, have over-predicted the degree of warming observed so far in the Niño-3.4 region.  Based on the model forecasts, the seasonality of El Niño, and the continuation of westerly wind bursts, El Niño is expected to strengthen and most likely peak at moderate strength. 

Expected El Niño impacts during October-December 2009 include enhanced precipitation over the central tropical Pacific Ocean and a continuation of drier-than-average conditions over Indonesia.  For the contiguous United States, potential impacts include above-average precipitation along the Gulf Coast, from Texas to Florida, and below-average precipitation for the Pacific Northwest.  Other potential impacts include a continued suppression of Atlantic hurricane activity, along with above-average temperatures and below-average snowfall for the Northern Plains.