Part 3 of the 2020 2021 winter outlook.

 

Today is the 1^st day of meteorological winter. So, it seems fitting that I release my 3^rd and final installment of the 2020-2021 Northeast Winter Outlook at this time.

Over the last few months, I’ve released parts 1 and 2 along with several post on the Facebook weather pages. If you missed the first two parts. You can find them in the links below.

 Part One

 Part Two

 Part 3 is going to build on parts 1 and 2. So, while I will retouch on some things and go into more detail on others, I won’t necessarily go over the same things.  

 This winter outlook Is the result of the culmination of several months of research, dealing with things like past winters, the teleconnections, global sea surface temperatures (SST), Northern Hemisphere snow growth and ice extent, solar activity, seasonal weather and climate models, and other things.

Before I get started, I want to point out, in spite of all the work that I do, on these seasonal outlooks. I want to point out, Short range forecasting is difficult; but long-range forecasting is much more challenging and imperfect. Seasonal outlooks are as much about science as they are an artform. They are designed to give a broad overview of what I expect to happen this winter in general. They aren’t designed to give details on when storms will happen, when it will be cold or warm. Nor are they about how much snow will fall in your backyard. They are about averages and cover the entire Northeast and northern Mid Atlantic.  So, while I try to be accurate. Most of my outlooks have been in the relative ballpark; but there have been outlooks that didn’t go the way I thought.  I have a degree in this stuff, but an outlook is just an educated guess as to what I think will unfold this winter. So always take them with a grain of salt, as they are painted with a wide brush.  

 

Well on to My official 2020-2021 Winter Outlook!

 

Last winter’s forecast wasn’t great!

Most of the winter outlooks for winter 2019-2020 were wrong.  Mine got some things right, and some areas turned out as expected. But for the most part it was a bust, at least according to me.

So, what happened?

Back in November of 2019 it looked like a sure bet that we were heading for a weak centrally based El Nino in the equatorial Pacific.  With the mild central Pacific SST and the warm pool south of Alaska. This set up normally means there is a lot of ridging near Alaska. This same general pattern was in place for the winter of 2013-2014. During the Summer and Fall of 2019 things were going as predicted. But once we got to December the entire pattern flipped and stood on its head. The Alaskan ridge collapsed. Other than a few brief occurrences of the Alaskan ridge, it was absent for the entire metrological winter, this pattern is called a positive EPO, which was the exact opposite of the negative EPO I thought would occur.   

Summer and Fall 2019 saw a lot of high latitude blocking near Greenland. But once we got into December, the blocking just disappeared for the most part. The models saw what was going to occur, such as the AO and NAO staying mostly positive; but I dismissed that idea, the fall pattern just didn’t support what the seasonal models were selling. But I was wrong on that as well.

The MJO stayed primarily strong in the warm phases of 5 and 6.

Another factor that I always look at is November temperatures.  November 2019 was substantially colder than average, based on the 1981-2010 average. Which tends to lead to colder and snowier conditions here in the Northeast. But when we look back, we can see that didn’t happen at all.  

The polar Vortex was another major culprit.  It stayed very strong and compact and sat over the North Pole for the most part.

All of these things and others conspired against me, and stabbed my outlook in the back.

 

Anyway, what about winter 2020-2021?

Analogs:

1933-1934, 1950-1951, 1954-1955, 1985-1986, 1995-1996, 1998-1999, 2005-2006, 2007-2008, 2010-2011, 2016-2017, 2017-2018  

 

1933 1934 had a similar pattern as we’re in now; the polar vortex tended to be situated on the North America side of the Pole.

 

 

Sea Surface Temperatures (SST):

Pacific SST:

 

El Nino Southern Oscillation (ENSO):

 

The ENSO is about SST in the tropical Pacific. Warmer than average temperatures are referred to as El Nino, whereas cooler than average temperatures are referred to as La Nina.

Looking at the SST chart, we can see the cooler than average waters in the eastern Pacific, these cooler than average temperatures have lasted for 3 months, meaning we’re currently in a La Nina. That will have a big impact on this winter.

 

 

Here is a look at the IRI/CPC plume, showing the Current La Nina should last through at least the winter.

 

 

Based in part on this NOAA seasonal forecast for December through February looks like this.

 

 

La Nina:

Images from Tropical Tidbits

La Nina continues to get stronger.

Right now, the La Nina is a strong sided moderate. So, this winter should feature a moderate to strong La Nina.  

Right now, the La Nina is basin wide across the Eastern and Central Pacific, but SST analysis does show, this La Nina is becoming more central based. A Central based La Nina isn’t good for snow on the East Coast; as it typically brings about warmer temperatures and less snow.

During La Nina, the polar jet stays a bit farther north, and the Subtropical Jet is less active.  This setup leads to less chances for nor’easters; doesn’t mean we won’t see any, just means that the odds favor having fewer Coastal Storms.

The strength of the La Nina should alter the course of the northern Jet, and force it farther west and north than usual this winter. The Jet Stream in this orientation would likely lead to more in the way of western runners moving over the Great Lakes or running along the Appalachians. This type of storm track would mean eastern Pennsylvania, eastern New York State, New England, and the Middle Atlantic would be at a higher risk for mix/ice/rain events instead of snow.  Western runners do tend to produce lake effect snow as they move away. So closer to the Great Lakes and far Northern New York State and Northern New England, would have the best chance of seeing average to above average snowfall. But that will depend on the timing of any cold air we do end up seeing.  But being primarily on the eastern side of the storm track will make it harder to hold onto any lasting snowpack.   

The Northeast Pacific Heat Wave:

We have the warm blob in the Northwest Pacific; but the entire northern Pacific very warm.

That warm blob and warm northern Pacific in general is going to want to promote a strong Pacific Jet, which could lead more of a zonal west to east flow. This would allow for a general mild Pacific flow as opposed to more of a colder Arctic flow.

The well above average SST anomalies in the Northeast Pacific, is a dual sword, while it does support the idea for a general zonal flow, it also would indicate a greater chance for at least some cold air outbreaks in the Northeast, and increase the chances for some snowfall depending on timing.

Indian Ocean SST:

Warm SST here leads to increased thunderstorm activity over the Indian Ocean, tends to signal a warmer winter over the Eastern CONUS.  If the Thunderstorms move into the Pacific that can be an indication for colder temperatures.  When we add in the La Nina. The thunderstorm activity should stay primarily over the Indian Ocean this winter.  Not good news if you’re a winter weather fan.

 Atlantic SST:

 For the most part the entire Northern Atlantic is warm; this is especially true in the Northwest Atlantic off the northern Mid Atlantic and New England Coast.

Early in the season the warmth off the East Coast most likely will promote general ridging over the Mid Atlantic into the Northeast.

 We do have the cooler SST south of Greenland and west of Ireland.

  

The Teleconnections:

The Quasi Biennial Oscillation (QBO):

The QBO, is a measure of stratospheric winds in the tropical Pacific that alternate between West to East every 12-15 months?  It normally works hand in hand with the ENSO. So, during a La Nina the QBO is typically negative. But this year it’s completely out of phase with the ENSO.   Usually a negative QBO helps promote a weaker Polar Vortex. But with the QBO looking to stay positive this winter. It will help strengthen the Polar Vortex. We very well could see the PV act like it did last winter, staying strong up around the North Pole with very limited excursions into lower North America.  This would lower our chances for a lot of cold air outbreaks. 

 

Pacific Decadal Oscillation (PDO):

Is another thing that has to be factored into this upcoming winter. The PDO involves sea surface temperatures in the North Pacific. The cycle typically last for 30-50 years.  Currently we’re in a cold phase. This means it will tend to amplify the effects of the ENSO in whichever phase it’s in. So, with the PDO being in the cold phase, it would help out the La Nina currently going on. With the La Nina looking to be on the strong side, this would increase our odds for overall temperatures in the Northeast and Middle Atlantic to be warmer than average.

 

The Pacific North American Pattern (PNA):

The PNA is a very important teleconnector for North America. When we have a positive PNA, we tend to see ridging on the West Coast into Western Canada, while the East Coast ends up seeing more in the way of troughing. When the PNA is negative we see the exact opposite. Currently the PNA is positive. I think the PNA is going to stay predominately positive to neutral for the next 4 to 6 weeks. Then It should flip to negative for the middle into the end of winter. This would mean the winter would be more likely to be front loaded.

 

The East Pacific Oscillation (EPO):

The EPO is all about the flow pattern across the Eastern Pacific. When the EPO is positive, we typically see a flow of milder Pacific air flow into the West Coast. The zonal flow that results tends to keep the northern half of the CONUS warmer. During the negative phase there is primarily a ridge in the eastern Pacific and over the West Coast; this in turn deflects the Pacific Jet north, where it has a tendency to dislodge colder air in Alaska and Northwest Canada into the Great Lakes and Northeast.

The Arctic Oscillation (AO):

The AO is a pattern of counterclockwise winds circulating around the Arctic. When the AO is positive the winds are strong and lock that cold air in the Arctic. When the AO is negative the winds become weaker and become wavier and distorted, allowing for colder air to penetrate southward into southern Canada and the U.S.

The North Atlantic Oscillation (NAO):

The NAO is an index that measures the pressure difference between the subtropical high pressure near the Azores and the subpolar low near Greenland. When the NAO is positive the East Coast tends to see higher heights leading to ridging, the opposite is true when the NAO is negative, when the East Coast sees more in the way of troughing.  The NAO is a big player in the storm track for the Northeast.    

With the QBO looking to be generally positive, it would indicate the AO and NAO to be overall positive. Here is a look at the teleconnection indexes from WeatherBell.

 

The Madden Julian Oscillation (MJO):

The MJO is a major player in worldwide weather patterns. 

The MJO is a large-scale disturbance of deep convection and winds that originates in the Indian Ocean it then propagates eastward across the Pacific. it forces strong intraseasonal variations in extratropical atmospheric circulations.  Because of this it has important implications for seasonal prediction.  Feedback for the MJO process has an influence in our neck of the woods here in the Northeast. The stronger an MJO is, the farther the dots lie from the circle. When the MJO is weak or not active, the values on the diagram will occur within the circle.  

The MJO consist of eight phases. To have an active and colder winter season here in the Northeast the MJO needs to primarily stay in phases 8 through 2. Generally, the Phases 4 through 6 tend to be warmer phases for the Northeast during December Through February.

Here is a look at the MJO Temperature and Precipitation Composites for the winter.

 

Currently the MJO is stuck in the neutral phase.

 

 

 

The MJO should primarily stay in the warmer phases 3,4 and 5 this winter. All the activity in the Indian Ocean right now is very important. Looking at the Indian Ocean we can see all that convection (thunderstorms), the thunderstorms are releasing heat into the atmosphere, this is going to pressure the pattern and atmospheric dynamics to favor those warmer phases.  

Sea Ice and snow growth:

I covered this in part 2. 

Snow extent across Eastern Siberia snow amounts have quickly advanced the last 10 days; they are now above average. Above normal snow cover extent in October, favors a strengthened Siberian high, cold temperatures across northern Eurasia and a weakened polar vortex/negative AO. But the snow extent western Siberia well below average. This is very important. Most of the time above average snowfall across Eurasia supports the development of high pressure over the area of snow. This year there is a lack of high pressure over Eurasia, this will interfere with the cold air transport, by reducing the chances of PV breaking down, splitting and migrating into the lower latitudes.   The lack of sea ice will also have an impact on cold air outbreaks. This winter setup would help North America have better odds of seeing any slippage of the PV as opposed of slipping over into Eurasia. So, if we do have a few Sudden Stratospheric Warming Events (SSW) this winter, they would be more likely to expand the cold into North America.   Maybe a bit of a wild card.

Snow Extent was well above average in October into the first part of November; but now North American snow cover has stalled and is now near decadal means. If this continues, it could be a stopper in the colder air outbreak bottle for the East Coast. This would help increase the strength of the PV.

Low sea ice would signal any blocking would be near and north of Scandinavia    That isn’t a good signal for a lot of cold and snow in the Northeast.  

The setup does support the idea of increased Ice Storm potential in much of our region.

 

The Polar Vortex:

 

 The Polar Vortex during a La Nina is typically stronger than it is during neutral or El Nino  conditions.

  The stronger the Polar Vortex the more likely the real cold air stays locked up to  the north, leading to overall warmer conditions in our region. 

The teleconnections are telegraphing the idea, that the PV will be overall strong during winter  2020-2021. I think this will especially be the case during the heart of the winter. If we have a Sudden Stratospheric Warming Event, it could throw a wrench into some of this idea. Leading to a weaker PV for part of this time period.  

 

 Solar:

 

All things being equal a weak solar tends to lead to a weaker Polar Vortex; but if other factors like La Nina indicates a colder signal then the sun activity won’t have as much influence.  

 

November:

 

As I said above, Conditions during November are a good bellwether for temperature behavior during the upcoming winter. Looking at the PRISM charts we can see November was very warm overall.  The first 2/3rds of November were unusually warm. So, the month ended as one of the warmest Novembers on record. In the past, most winters that saw warmth like this in November end up seeing below average snowfall.

  

The Bottom Line:

 

The areas most likely to experience major cold this winter will be across Western Canada into the Pacific Northeast, Northern Plains, into the Upper and Middle Great Lakes (including the Ohio Valley). While the East Coast and Southeast U.S will experience mild overall temperatures.

 

I think the real transition zone between the real cold air in Northern and Western Canada, and the mild  temperatures to the south and east, will setup just to our north for the most part. But I want to point out that overall warmer pattern doesn’t mean we won’t see some colder outbreaks, which would be enough cold for snow at times.  

The northern Jet should end up being quite active. I expect to see the southern Jet  becoming less active the farther in to winter we get, this would be typically during a La Nina.

 

I don’t think the entire winter will be a torch. The second half of December into the first half of January (maybe a little past mid month) will see at least a few extended periods of significant cold; this time period would see typical winter weather. So, there is a chance many of us could see a White Christmas, with at least some snow on the ground. December should end up with average to slightly above average temperatures overall.  As for the rest of January and February, I think we will see quite a few thaws; but it will be cold at times, as that colder air tries to work into the region, mid January toward mid February could see quite a bit of cold, if the analogs are right. If the Northeast is going to have a semblance of winter it most likely would be during this time. During January and February, we will be at risk for record warmth at times. January and February should end up overall above to well above average. 

 

 The most active storm track will be southwest Canada into the Northern Plains, then over the  Great Lakes into the Canadian Maritimes. This would mean the most common types of storms  would end up being Clipper type and a chance for a few Miller B type storms. Above average precipitation across northwest Pennsylvania, Western New York State and  Northern New York State (north of I-90) and Vermont, New Hampshire, and Maine.  Precipitation will be average across the rest of New England and New York State into  Pennsylvania. For Southern Pennsylvania into the Mid Atlantic precipitation will be generally  below average.

 

Given the idea of overall above average temperatures. Trying to figure out the snowfall part of this is rather tricky. Generally, for a large part of far Western New York State and Northern New York State along with Northern Vermont, Northern New Hampshire, and Central and Northern Maine, average to slightly above normal snowfall looks likely. The rest of the Northeast and Middle Atlantic will end up with overall snowfall below to well below average for Winter 2020-2021; but I think there will be more snow than last winter.

 

With the pattern that looks to setup, the Mid Atlantic, Pennsylvania, much of New York State and Central and Southern New England will be at an increased risk for Mix/Ice/ Rain events.  

 

The lack of real persistent cold would likely lead to below average ice extent on the Great Lakes. The pattern supporting the idea of less arctic outbreaks would mean less chances for lake effect snows. But with the lakes having less ice cover, when we do see those cold outbreaks, there would be an increased chance for heavy lake effect snow events. Due to this, Lake effect snow amounts could be closer to average.

   Well that’s it. I hope you enjoyed reading my three-part winter outlook for 2020-2021.