El Nino Watch: Milder winter ahead?

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Pacific Sea Surface Temperatures (SST's) show rapid warming in the tropical Pacific Ocean.

For the first time ever, the Climate Prediction Center (CPC) has issued an El Nino Watch. CPC's new advisory system is designed to give states and communities advance warning months in advance for seasonal weather changes and potential effects.

Tropical Pacific SST's have warmed to about 0.5 degrees above average. El Nino is defined when Pacific SST's remain at or above the +0.5 degree threshold for 3 consecutive months and 5 overlapping seasons. Various CPC computer models indicate Pacific SST's could warm to 1 to 2 degrees above average by next January. This would make for a moderately strong El Nino event.

In Minnesota and the Upper Midwest, El Nino events bring milder than average winter temperatures about 70% of the time statistically. There is also a trend for lighter than average winter snowfall.

Other U.S. effects include wetter than average winters in the southern states. States from California through the Desert Southwest and along the Gulf Coast to Florida tend wetter during El Nino events. This can be a good thing for areas that depend on snow and rainfall runoff in the mountain ranges feeding the Colorado River. Cities like Las Vegas, Phoenix, Tucson, and San Diego rely on water from the Colorado.

The last El Nino event occurred during the winter of 2006-07. During that time, Tropical Pacific SST's peaked at 1.1 degrees Celsius above average. We had a mild winter in Minnesota. Here are the monthly temperature anomalies in the Twin Cities for that winter season.

November: +3.7 degrees

December: +9.6 degrees

January: +6.1 degrees

February: -4.2 degrees

March: +8.0 degrees

Of course there is no guarantee that temperatures will be that mild if El Nino occurs this winter. But it's nice to dream!

PH