2020- 2021 NORTHEAST WINTER OUTLOOK
Let me start off with...... I'm not expecting this to be the coldest of winters, rather short but meaningful cold snaps will be followed up by mild air at times..The impact on snowfall will come down to timing and phasing.
Most everyone has heard of El Nino and La Nina, especially when talking about the winter outlook. This is refered to as ENSO (El Nino Southern Oscillation) There are other "oscillations" in the atmosphere that affect our weather. However, ENSO is the only one that is linked to the ocean temperatures. This is important for two reasons. First, there is a lot of skill forecasting our ocean temperatures. Second, the ocean temperatures don't suddenly change. These two facts allow us to predict the atmosphere several months into the future. Most of the other oscillations are purely atmospheric. As such, they can only be predicted 1-2 weeks into the future with any skill making these oscillations much less predictable, the result is blindsiding a forecast by altering or even overriding the effects of ENSO.
All that being said this Outlook will lean on ENSO just the same.... So what is the Current state of ENSO.
To me January through February look to be the snowiest months of the winter. Every forecast made months into the future are based on science Data and Analogs.La Niña is the theme for this upcoming winter, this is when cooler than average ocean temperatures are noted in the Pacific We get these changes in ocean temperatures from our trade winds that blow in the tropical latitudes, so for this winter we will have La Niña conditions. Here is a look at the overall La Nina set up.
The result here is shown on the map below for what La Nina conditions are likely to bring over the winter.
CLOSER TO THE COAST
JUST OFF THE COAST
ANALOG YEARS THAT MATCH UP WELL
Analog years are when we look at the past matching the ENSO phase as well as the other climate drivers that are expected to play an important role in the upcoming season. The best Analogs for this season appear to be notably 1983-84, 1995-96, and 2017-18. This La Nina is really not like others of the past..there is still a lot of warm Ocean out there in the Pacific..so how it performs will be a week to week, month to month thing..I will make changes to this outlook as needed.
AN ACTIVE NORTHERN STORM TRACK
The Pattern screams active in the storm department but mostly from the North..With the la Nina in progress I would expect a weaker southern stream of the Jet..This will also aid in keeping any SE Ridging at bay but does not mean it won't pop up from time to time, So I expect frequent energetic disturbances along the northern stream branch of the Jet. Could things go wrong like last year..yes of course..this is a long range outlook and should never be relied upon to make any decisions as the best weather forecasting still comes from 3-4 day's out.
Also with a much more active Northern storm Track positioning is important here..If the Track screams out of the Lakes we should expect redevelopment off NJ or LI..Development Off LI would put a damper on snow amounts for southern New England south to the Mid Atlantic while Development off NJ would favor NEPA NJ Northward.
I believe there will be just enough Southern Jet to favor the Baroclinic development region to be close to the DE NJ coasts and this is also why the snow amounts go up as you head North, but not all storms will develop there..the real possibily of seeing coastal huggers remains on the table.
Taking this into consideration we than look at the position of the Polar Vortex..I've seen some model shifting the past few weeks leading me to believe we will see quite a bit or Ural Blocking..This should keep the Polar Vortex on it's toes and very suspect to disruptions..This is why I started this off with Sharp Cold outbreaks with a warm return. We need to also note that should we get a stronger southern jet than currently noted a Zonal flow would be more likely thus locking the Polar Vortex up to the North.
Remember that La Nina brings a weak southern Jet stream, when the Jet Stream weakens it becomes wobblier, this allows cold air to move southward, since this is a la Nina I will lean on this idea for now as there is already signs of a weaker southern jet..one only has to look at the Dry conditions in California with the wild fires.
Now the Million Dollar question is "What will the winter be like?"
As it looks right now A combination of favorable atmospheric and oceanic circulation patterns will exist along with support from several analogs of similar years indicate that a more active Northern storm track will be the rule this year. This combination could set the stage for several big winter storm events for the the East Coast, especially from late January into most of February.
We all remember the 2014 record setting winter with seemingly endless piles of snow. I stayed up around the clock creating Storm Maps and as major Northeast cities accumulated a snowfall surplus of 15 - 30+ inches. In fact, Philadelphia recorded their 2nd snowiest winter of all time with 68.0" and New York's Central Park finished with 57.4", the 5th snowiest. Along with the snow, frigid temperatures dominated with places like Hartford CT seeing 44 days of at or below freezing temperatures. Coming off such a brutal winter, will this winter analog bring back the onslaught of cold and snow or will a milder winter be the rule? Well I do not expect to see snow amounts fall in the well above normal range really for anybody, I more expect the winter to get going on Mid January and last through February..so we're talking about a 7 week period.
So on the flip side those looking for a balmy winter like last year you're out of luck this year, if anything I see more of a split between cold and warm shots. Neither one looks prominent at this time. I would expect more transient Temperatures nothing with a lasting foot hold.
I even looked deeper this year and found that almost all of the past winters with similar characteristics to the expected pattern this year have featured Seasonal cold but had their warm spells. These years include 1976-77, 1977-78, and 1993-94. These winters produced a few Blizzards, I don't expect to set a new Record this winter but i do expect much more snow than seen last year..not hard to do.
With all the being said Here is my 2020-21 winter outlook for the Northeast and Mid Atlantic states.