2020 2021 winter outlook part 2

 

Welcome to my 2^nd installment of the 2020-2021 Northeast winter outlook.

I want to apologize; this 2^nd installment is a couple of weeks late. I’ve been much busier than I thought I would be. Who knew, running a horse ranch, running a private business, and raising a family, and posting weather for all y'all could be so busy?  :)

 

I’ve been getting a lot of questions from y’all asking what the winter will be like.  Winter lovers want to see a lot of cold and snow, while those who don’t look forward to winter, want warm and less snowy weather.

Some of the questions have asked for specifics on how the winter will fair for their hometown.    I wish I could give you that kind of exacting detail. But there is no way I can get that kind of detail over an entire winter season.  A winter outlook is basically just an overview of what I generally think the winter will turn out for the Northeast and Northern Mid-Atlantic Region. The analysis I provide is detailed, but I can’t tell when a storm is going to pop up or how much snow will fall on a particular day.

 

The first installment for this winter’s outlook can be found here.

 

Sea Surface Temperatures

 

The El Nino Southern Oscillation (ENSO):

The ENSO is all about the water temperatures in the equatorial Pacific.

 

La Nina:

La Nina Is when we see colder than average (Blue) equatorial Pacific water in the Eastern Pacific. To be declared a La Nina Pacific equatorial water temperature that is cooler than average by at least 0.5, for at least three consecutive months

La Nina is basically the cooling of the equatorial Pacific SST across the eastern into central Pacific and warming SST in the western Pacific. We have to remember not all La Nina’s are the same, so, there can be a lot of variations in the atmospheric pattern that develops. 

The much colder than average waters in the equatorial Pacific are pushed right up to the Coast of South America.  Right now, we’re seeing moderate La Nina conditions. But the La Nina is getting stronger. So, this La Nina will likely be moderate to strong. From what I’m seeing I believe the La Nina will end up on the strong side. A strong La Nina is when SST are at least 1.5 colder than average. The latest ocean temperature data, is showing we are at or could be very soon at this temperature threshold.

 The La Nina is going to last through the winter of 2020-2021, and at least well into Spring of 2021.

We won’t experience the full extent of this La Nina until January. So, a true La Nina pattern would likely be sitting up after Mid to late December. During a strong La Nina we often see warm air get drawn up the East Coast into the Mid-Atlantic and Northeast. A strong La Nina also tends to cause the Polar Jet Stream to be quite strong. This helps stop high latitude blocking from forming. This can also lead to a warm winter and a general lack of wintertime precipitation. Now if the La Nina becomes more central to west based; it would increase the odds of a strong sustained ridge over the eastern CONUS. If this does occur, we would see the AO and NAO stay mostly positive over winter 2020-2021. 

The Quasi-Biennial Oscillation (QBO):

The QBO shifted from an east (negative) phase we saw over the Summer into early Fall, to a west (positive) phase over the last 4- 6 weeks.  While a positive QBO can help bring about a colder pattern; it also means we tend to see more in the way of weak to moderate wintertime events.

 

Arctic Sea Ice Extent (SIE):

The volume of sea ice in the Arctic, is near a historic low value. This is especially true in and around the Barents-Kara Seas and Alaska. Warm temperatures in the Arctic are widespread. But as the SIE indicates the warmest temperatures are around the Barents-Kara Seas.  When the amount of Arctic sea ice is low, we lean in the direction for a greater likelihood for a strong temperature gradient to set up between the Arctic Ocean and Canada and the United States. This can have an influence on the pattern, to allow for a greater chance for disruptions in the Polar Vortex to occur. If this occurs, we would have a better chance of seeing at least some cold air in the Eastern U.S. this winter season.  I would classify the amount of sea ice as a wild card this winter. So, it could go either way.

 

 Eurasia and North America Snowfall:

 

We look at northwest Eurasia and Siberia for a clue has to how winter in North America could unfold. The amount of snow growth in Siberia below 60° North, is a very important indicator about the chances for high latitude blocking over Greenland. The first half of October did see an expansion of snow across northwest Eurasia into Siberia. But that has since faded a little. Right now, Eurasia snow cover does look to be average to slightly below average.  Blocking over Eurasia has been lacking since Mid-October. This isn’t a good sign if you’re a cold weather fan. But there is still time for snow extent across Eurasia to improve.

 

We have had decent snowfall in northwestern Canada and Alaska. A deep snowpack here, allows for formation of polar and arctic airmasses, these cold air masses can drop into the CONUS resulting is cold air bouts.

 

 

Solar Activity:

The Sun has been relatively quiet for first few months of the new solar cycle. Whereas the previous cycle had at least 6 months of no sunspot activity, now we’ve started to see some smaller sunspot regions popping up here and there. I expect the Sun will slowly become more active as we move through winter 2020-2021.

 

 

Bottomline:

 

Temperature:

 So far, November has been warm here in the Northeast and Mid-Atlantic. Typically warm La Nina Novembers tend to see mild warmer conditions during the winter.

The combined effect of the La Nina, the sea ice extent more extensive across Asia due favor overall well above average temperatures all along the East Coast and across the southern US, including Texas. 

The setup, at least for now, looks to promote troughing across the western part of North America, with ridging being more prominent across eastern North America.

With what looks to be pronounced negative height anomalies in the Arctic; my thinking is it will encourage the AO and NAO to be more in the away of positive this winter.

 Right now, given everything, I think December is going start more on the cold side, it should end up overall with slightly above average as far as temperatures go.  Once the La Nina really kicks in January and February will see a volatile temperature pattern with overall well above average temperatures for the Northern Mid Atlantic, Pennsylvania, a large part of New York State and Southern New England.

Northern New England and Northern New York State would see overall average to slightly below average temperatures.

 Snowfall:

A lot is going to depend on how strong the La Nina becomes. Another thing that will factor in, will be just how much high latitude blocking we end up with. A weak La Nina increases the odds for more colder periods, along with a more favorable storm track for more in the way of snow.  With the storm track bit more north, northern New York State and northern New England will have a better chance of seeing closer to normal snowfall, whereas the southern tier of New York State, Southern New England, as well as Pennsylvania and the northern Mid Atlantic would have a better chance of seeing well below average snowfall this winter.

Here is a couple of maps that show how snowfall amounts can differ during a weak La Nina and a strong La Nina.

 

Because of the northern primarily storm track, many of those areas in Pennsylvania, I-95 Corridor, along the Coast, as well as Maryland and Delaware, will see well below average snowfall. With a possibility of the same places that experienced the snow drought last winter could see a repeat performance this winter.  But this area will be at a higher risk for bigger rain events as well as an increased risk for ice events. 

 

New York State along and south of I-90, as well as southern/ into Central New England will see average to below average snowfall. Northern New York State and northern New England have a shot at overall average to above average snowfall; this will be especially true for the Adirondack, Green, and White Mountains.  But with the temperature pattern looking to be fickle, we could see a general lack of snowpack, which would be similar to past winters.

There is still time for things to change, so we will see.

I will try to have my final part 3 installment posted  by the 2^nd week of December.