UPDATE ON LA NINA
Written By: Scott Hetsko & Climate Prediction Center
I read with much interest the update on La Nina from the Climate Center.
La Niña continued during September 2010 as reflected by the large expanse of below-average sea surface temperatures (SSTs) across most of the equatorial Pacific Ocean. All weekly Niño SST index values were between –1.3oC and –1.8oC at the end of the month. In addition, the subsurface heat content (average temperatures in the upper 300m of the ocean, remained below-average, reflecting a shallower-than-average thermocline in the central and eastern Pacific.
Convection remained enhanced over Indonesia and suppressed over the western and central equatorial Pacific. This pattern was linked to a continuation of enhanced low-level easterly trade winds and anomalous upper-level westerly winds over the western and central equatorial Pacific. Collectively, these oceanic and atmospheric anomalies reflect the ongoing La Niña.
Consistent with nearly all of the forecast models, La Niña is expected to last at least into the Northern Hemisphere spring 2011. Just over half of the models, as well as the dynamical and statistical averages, predict La Niña to become a strong episode (defined by a 3-month average Niño-3.4 index of –1.5oC or colder) by the November-January season before beginning to weaken. Even though the rate of anomalous cooling temporarily abated during September, this model outcome is favored due to the historical tendency for La Niña to strengthen as winter approaches.
What this means for us is a variable Winter with a few storms that could favor significant snowfall for Western New York. The only trouble with a La Nina storm track is that we are close enough to see messy mix type storms as well.
Scott,
ReplyDeleteDo you think the potential for another year of intense polar blocking due, in part, to continued low solar activity, could throw a monkey wrench into the overall forecast for our area?
Just look at last year, when so many experts were caught off guard by the extremely negative AO and it's influence on their forecasts that were based mostly on a typical el nino pattern.
I ask because I am a bit concerned by what another deeply negative AO winter could mean for us this winter.....this time during a powerful la nina.
There is more to analyze that just La Nina for sure. It's solar activity, ocean temperatures, polar and mid latitude jetstreams. So you're right in that you can't just rely on ONE thing for your forecast. The question becomes: "Which pattern will dominate" I'm not sure we will know that answer until late November if at all.
ReplyDeleteThis is one of the reasons that I won't put out our Winter Outlook until late November. This year our Winter special will air 11/20, look for the prediction at that time