Great Weather Ahead

In the short term, the good weather will continue and even warm up next week.  Although some big changes are coming down the line (more on this later), we will have to enjoy the short sleeve weather when we get it.  So what we have is an area of high pressure dominating the weather across the eastern half of the United States. The weather will be great for the Game of the Century tonight (LSU 24 Alabama 20).  Here is the surface map...
Click to enlarge
Because air flows in a clockwise manner around a high pressure system, our "air" is currently coming from Canada, therefore it is cool and dry.  However that high pressure area, currently centered near Toronto, will slide southeast, flipping the north wind to a southwesterly wind.  That will allow for temperatures to moderate.  As long as the sky cover is mainly clear, I see most places getting into the upper 60's and MAYBE low 70's on Tuesday and Wednesday.   We are currently experiencing a positive phase of the North Atlantic Oscillation (NAO), which generally means warmer and wetter conditions in the Eastern United States.  What happens is low pressure forms near Greenland/Iceland and becomes stationary, therefore "blocking" storms from travelling off the east coast.  Instead, they cut up along the Appalachian Mountains and we see warm temperatures.
The top forecast is the one to look at; red is forecast, black is the past- from NOAA
The next system looks like its going to moving in by Thursday evening; this timing will probably change.  A wet event is forecast, due to the mild temperatures and overall pattern.  Behind this system things become interesting.  As seen above, the NAO is forecast to return to its negative phase.  The models also agree, pumping some deep cold into the United States.  Looking at the long range GEFS model, one can see deep cold in the Arctic regions.  However, models are famous for breaking down patterns too quickly.  While we will return to a cold pattern by the end of the month, exactly when this occurs is not settled.  I'm going to say that the models have the right idea, they are just a bit quick with the pattern.  That means I expect a cold Thanksgiving in the east.

So today temperatures will struggle to get to 50.  Tomorrow will be warmer, but sunny.  Dress warm and stay hydrated if you are going to the Patriots game. By Monday temperatures are beginning to creep back towards 60.  Tuesday will be mild for November, temperatures in the mid 60's.  I like Wednesday or Thursday to approach 70 before the rain system moves in.

Overnight lows will be moderating over the next few days.  Tonight will be in the upper 20's, tomorrow night upper 30's, before settling in the mid 40's for the next few days.  Enjoy the nice November weather, it's not going to last too long!

November-December Forecast
I expect a cold later third of November and December for much of the United States.  The projected negative NAO, a ramp of extra-tropical Pacific systems, and a La Nina will cause headaches for many as they try to get ready for the holidays.  The most recent analog to December 2011 is December 2008, which is infamous for the Ice Storm (people out of power for 3 weeks) and a pair of systems around December 20th that combined to snow for 46 out of 48 hours in Northbridge.  Here are analogs from 1950, 1955, and 2008.

These are from the Physical Science Research Division of NOAA.  I used the 1950-95 long term average, but the cooling becomes much more pronounced when you look at averages from recent years, (ie 1993-2007 etc; try it yourself here).    The real interesting question is whether or not El Nino will return in 2012.  A neutral state seems likely given a cold PDO; however one can't be ruled out as this La Nina may recharge enough heat that it can be released over the next 8-14 months.  How much heat is released or absorbed in the Pacific plays a critical role in climate, whether you want to believe it or not.

While its nearly impossible to predict what the NAO will do, I think after it switches to negative it will lock in for a rough early winter.  My goal for this blog is to be out in front of things, to have people aware of the general weather pattern.  Go Bruins tonight, Pats tomorrow.  


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