El Niño–Southern Oscillation (ENSO): What is it?

Normal conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC Normal conditions in equatorial Pacific Ocean Warm water in the western Pacific Cold water in the eastern Pacific

Normal conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC Normal conditions in equatorial Pacific Ocean Deep convective storms and heavy rain concentrated over warm water in western Pacific Warm water provides “fuel” for storms

Normal conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC Normal conditions in equatorial Pacific Ocean Walker Circulation is in place Rising air over western Pacific, sinking motion over eastern Pacific Winds: easterly (east to west) at surface, westerly (west to east) aloft

Normal conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC Normal conditions in equatorial Pacific Ocean Upwelling brings cold water to the surface near the western coast of South America

El Niño conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC El Niño conditions in equatorial Pacific Ocean Warm water spreads eastward across the Pacific

El Niño conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC El Niño conditions in equatorial Pacific Ocean Convective storms shift eastward into central and eastern North Pacific, remaining fixed over warm water Location of convective storms varies from event to event

El Niño conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC El Niño conditions in equatorial Pacific Ocean Walker Circulation weakens Surface easterlies weaken or become westerly Upward motion develops over central/eastern Pacific

El Niño conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC El Niño conditions in equatorial Pacific Ocean Upwelling decreases in eastern Pacific and warm water reaches coast of South America

La Niña conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC La Niña conditions in equatorial Pacific Ocean Big difference in sea surface temperatures between western and eastern Pacific Warm water in western Pacific, cold water in eastern Pacific

La Niña conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC La Niña conditions in equatorial Pacific Ocean Convective storms shift westward, remaining fixed over warm water

La Niña conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC La Niña conditions in equatorial Pacific Ocean Walker Circulation strengthens

La Niña conditions in equatorial Pacific Ocean North America Southeast Asia South America Australia Source: NOAA/CPC La Niña conditions in equatorial Pacific Ocean Upwelling increases in eastern Pacific, and water is cold along coast of South America

Tracking the evolution of ENSO Sea surface temperature departure from average over central equatorial Pacific – a commonly used ENSO measurement El Niño La Niña Source: NOAA/CPC Highly variable with lots of fluctuations; no regular cycle El Niño or La Niña events typically last 9–12 months, sometimes even longer On average, El Niños and La Niñas occur every 3–5 years Impacts on ocean and atmosphere usually most significant in Northern Hemisphere

Ocean temperatures for past El Niño and La Niña events Strong El Niño event Strong La Niña event Source: NOAA/CPC

Sea surface temperature anomalies Current Conditions Sea surface temperature anomalies 3–30 January 2016 Cooler than normal Warmer than normal Source: NOAA/CPC

Outgoing longwave radiation anomalies Current Conditions Fewer clouds/rain than normal Outgoing longwave radiation anomalies 3–28 January 2016 More clouds/rain than normal Source: NOAA/CPC

Links to animations Recent evolution of Pacific sea surface temperatures: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/sstanim.shtml Comparison between 1997 and 2015 sea surface temperatures: https://youtu.be/whsQbIwWjBo

Impacts of El Niño on wintertime weather over the U.S.

El Niño’s typical impact on wintertime weather over the U.S. Warmer than normal across northern U.S. Wetter than normal across the southern U.S. Drier than normal over northeastern U.S. Source: NOAA/Climate.gov

Temperature relative to normal How has El Niño affected the U.S. in past winters? 1982–1983 1997–1998 Temperature relative to normal Cooler Warmer Precipitation relative to normal Source: NOAA/ESRL Drier Wetter

Temperature relative to normal What about this winter? It was super warm in December 2015 over the U.S….and across the globe Global temperature time series for all Decembers on record Temperature relative to normal Cooler Warmer Source: NOAA/ESRL Source: NOAA/NCDC 1880 2015 Warmest December on record for Albany, for New York State, for the U.S., and for the entire globe!

What about this winter? …and it has been raining/snowing a lot in some areas Precip anomaly for Nov 2015–Jan 2016 Precipitation relative to normal Source: NOAA/NWS Drier Wetter

Drought conditions in early October 2015 Source: National Drought Monitor

Current drought conditions Drought has improved in many areas in the West! Source: National Drought Monitor