El Nino: How past El Nino's have worked out for western AK

By Rick Thoman
Alaska Climate Specialist
Alaska Center for Climate Assessment and Preparedness
International Arctic Research Center/University of Alaska Fairbanks

With El Niño well underway now in the tropical Pacific, this week's Climate Watch looks at how past El Niño autumns have worked out.
As a refresher, El Niño refers to the prolonged occurrence of well-above normal ocean surface temperatures in the central and eastern Pacific Ocean near the equator, which in turn influences the preferred areas of sustained big tropical thunderstorms, and these in turn effect the higher latitude jet stream and associated storm track. Because the ongoing El Niño is very likely to push sea surface temperatures to near or above record high level, I've eliminated weak El Niños (where ocean temperatures were only modestly above normal) from consideration. That leaves 13 autumns since 1970 when moderate to very strong El Niño conditions were present.
This week's graphic plots the September to November total precipitation (top) and average temperature (bottom) as the difference from normals that were used at the time. Overall, El Niño autumns have been slightly wetter and warmer than normal. The correlation is strongest for precipitation: only two of 13 autumns were substantially drier than normal, while four autumns were colder than normal. 2009 in particular was much colder and drier than normal, while 1994 was seventh coldest autumn since 1941. So while El Niño tilts the odds toward mild and wet, because there are other drivers in the Arctic weather climate system like sea ice conditions and ocean temperatures outside of the tropics, it really is the case that “anything could happen.”