Sunday, November 17, 2013

The Pattern Ahead And Some Winter Thoughts

Overall it has been a very quiet Autumn thus far in Southern New England, temperatures have been up and down just like we are accustomed to this time of year. Many locations saw their first flakes and also their first minor snowfall accumulation and it came right around the average date that it should do so. We have seen some strong cold front passages this season , but they have come with little fanfare in the precipitation department. So, as we now are just past mid month November, where do we stand compared to the mean average of years past in both temps and precip?..The graph below shows the numbers of each. (Click all images to enlarge and please do not redistribute)
So now the big question, how does it look moving forward as we head towards late Autumn and approach the beginning of Winter? I am seeing signals of a pattern change starting as early as mid to late week upcoming. The pattern as of late has been a northern branch dominant one, again not uncommon for this time of year. As we approach December those northern storm tracks tend to shift further south leading to increasing opportunities for the northern energenic branch to phase with the moist southern branch of the jetstream leading to the increase in storm development over the south and south central United States. Step one is to first get a pattern that becomes conducive for storm development in locations that typically are the breeding grounds for storms to then approach the East Coast then either make the ride all the way up to the US /Canada border or depart the coastlines father south at some point. Its that time of year where we need to start watching for these potentials.
In recent years those that are "snowlovers" have almost come to expect a snowstorm in November and even October. Not the case this year, at least so far. Changes start next week and energenic disturbances to the north will start to descend further to the southern United States allowing for a more amplified pattern to take shape. There currently are no strong signals that this leads to any type of storm just yet but surely is an indication of a pattern becoming more conducive for development. That is apparent in the graphic below which shows the 500mb Ensemble  Mean 
 and "spaghetti plots"  as we approach mid to late next week. Showing amplified trough and northern (blue) and southern(red) streams getting closer to interaction.
Again, none of this indicates a set in stone storm or that one will develop, but they can and should start to as early as the upcoming weekend. One other graphic to show you is the favorable teleconnections starting to point in that direction as well. 1st is the North Atlantic Oscillation (NAO)..Which represents Upstream Greenland Blocking in a negative phase. Also conducive for storm development hovering around Neutral. Next is the Pacific/North American Pattern (PNA) which in a positive or trending positive phase develops a ridge across the western US which tends to lead to a trough over the east. Lastly is the Arctic Oscillation (AO) which is just as the name suggests , provides arctic air and a negative or trending negative phase usually does the trick. So, nothing set in stone yet, but its the conduciveness that has me keeping an eye on model as we approach December. 

All signals I have gone over and all that I continue to see as the days pass continue to point to a "traditional" winter over the Northeast. This means the snowiest periods should occur in December, especially mid to late month into 1st half of January . Appears a very cold February is in the cards along with a major storm threat early to mid month. Normal snowfall and temperatures should be the rule through March into April. As of now I feel near normal to slightly above normal snowfall is in the cards for the Northeast this winter season. Thank you for reading !   ~Anthony 

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