Saturday, November 10, 2012

No Official Nino Likely This Winter

While ocean temperatures in the "Nino regions" of the Pacific are slightly above average right now and have been for a while, the temperatures have by and large stabilized and have not trended further towards El Nino status.  The development of a Nino was the concern of many forecasters (and ourselves) earlier this Spring when it looked much more likely that a Nino would in fact develop over the Pacific this summer and carry over into winter.

That's not to be.

Temperature anomaly of the Eastern Pacific's Nino region (from 11/8)

The murky, mushy middle sometimes referred to as "La Nada" looks likely.  Such winters are a mixed bag for us and result in a weather pattern that can be driven much more heavily by high latitude blocking (NAO, AO) than it is by factors in the Pacific.   El Nino tends to enhance the subtropical jet stream, which can provide additional moisture for East Coast storms and if blocking is just right along the East Coast, your snow odds increase.  See three winters ago (2009-10) as evidence of this.

NOAA recently dropped their "El Nino Watch" in a discussion they released on Thursday but do note that sea surface temperatures in the Eastern Pacific will remain slightly above average through the course of winter.

"While the tropical ocean and atmosphere may resemble a weak El Niño at times, it is now considered less likely that a fully coupled El Niño will develop," stated the CPC in their discussion.

Most modeling forecasts around the Nino right now state things hold "steady state" through the winter as a consensus...which means slightly above average ocean temperatures in the Eastern Pacific but not warm enough (usually close to a degree or more Centigrade above average) to justify a Nino.