Thought it was time to update a few of the posts in the last several days with some of my latest thinking.
Friday Night/Saturday Morning Storm
The models have backed away from the 12z Euro showing a major “bomb” over New England with impressive CCB snows down to the coast. I’m not surprised as sometimes you can get one run that really shows things exploding then everything backs off. With a deep closed low and plenty of dynamics I still think there will be some wraparound flurries but accumulating snow doesn’t seem terribly likely. Wind will be an issue overnight Friday and I think 50 mph wind gusts are possible in some towns with rapid pressure rises and a strong pressure gradient as the low departs to the northeast.
Pattern Change – Delayed But Not Denied?
The key to this pattern change is what’s going on in the north Pacific and particularly in the Gulf of Alaska. For the last 2 weeks a very strong series of upper level lows has brought brutal cold and storminess to Alaska and has driven a monster jet into British Columbia. Whistler ski area northeast of Vancouver has had their snowiest November ever. This jet stream setup as flooded the continent with warm, Pacific air. No good.
The 12z GFS Ensembles do show this pattern breaking down by day 7 (next Monday or Tuesday) with the trough over Alaska being replaced by ridging which essentially kills the north Pacific jet. The +EPO which has flooded North America with warmth will switch signs and become negative. This teleconnects to big cold in the northern Plains and northern Rockies as it allows the Polar Vortex to swing south east of the continental divide. On the right you can see the surfadce temperature and 500 mb height anomalies with a +EPO pattern. Our pattern the last several weeks resembles this. The models agree on no
sustained blocking in the North Atlantic, but a wholesale shift in the Pacific. On the left is a composite for a -EPO/+NAO regime and you can see near normal height anomalies in the northeast and strong negative anomalies in the northern Rockies/northern Plains. What El Nino???????? At least for December 1-7 this is what the GFS ensembles and Euro ensembles seem to indicate so though the pattern has changed I don’t think we’re going to do much better than average in the northeast with the potential for above normal (+1/+2) given an awful storm track through the Great Lakes.
As I expected the MJO keeps on trucking. Should be entering Phase 6 by Turkey Day and out of the Maritime Continent toward more favorable SSTs over the west Pacific. You can actually see today the MJO index gained quite a bit of amplitude putting to rest to thought that this MJO wave was going to die out. Eventually this wave will reach the Dateline and given high SST anomalies back in the Indian Ocean I have no reason to believe we won’t see another MJO wave develop on this one’s heels.
December 1-7th Call
Given the GFS/Euro ensembles decent agreement in a strong -EPO ridge developing with little sign of north Atlantic blocking I’m reasonably certain that the northern Plains/Rockies will average below average in this time frame. Here in southern New England I’m expecting just above normal temperatures thanks to a storm track that will favor the dreaded Lakes Cutters.
I’ll try and have a month of December call out in the next few days!