2022 2023 winter outlook for the Northeast part two

 

Welcome to part two of my 2022-2023 winter outlook. Part, one went into this seasons triple dip La Nina, a few teleconnections, and the Hunga Tonga Volcanic eruption. Part one, showed how both of those are arguing for a colder than average winter for a large part of the Northeast.  Part two will go into the Pacific Decadal Oscillation, the Eastern Pacific Oscillation, the Quasi Biennial Oscillation, and the Pacific North American Pattern, and how they detract or enhance the atmospheric effect of the La Nina and Volcanic eruption. Part two will go into possible storm tracks we should see this winter. As well as some thoughts on the Polar Vortex. I will also go more into analogue winters and make some adjustment from part one.

 2022-2023 winter outlook part one

Teleconnections:

 

Pacific Decadal Oscillation (PDO):

The PDO is a change in the Sea Surface Temperatures pattern in the North Pacific Ocean above 20-degree north latitude. Like all teleconnections the PDO has a positive (warm) phase and a negative (cool) phase. Generally during the positive phase, warmer SST exist along the Northwest Coast and West Coast of Canada. During the positive phase the wintertime temperatures tend to be warmer across the western CONUS and cooler in the eastern CONUS, during the negative phase the opposite is generally true. The Phases of the PDO can enhance or diminish the effects caused by the ENSO. So, when we have a negative PDO during a La Nina, it can increase the impacts on temperature and precipitation patterns typical of La Nina. The last two winters involved negative PDO’s.

When we look at the SST in the northern Pacific, we can see those warm SST off the West Coast south of Alaska. It seems the PDO is starting to turn positive.

 

The La Nina, PDO and the Hunga Tonga Hunga eruption will make this winter very distinctive:

As I said in part one, this winter is going to feature a triple dip weak to moderate East Based La Nina. The fact that we look to see a positive PDO during this coming winter, is a big deal. Every other triple dip La Nina had a negative PDO. So, therefor they enhanced the La Nina in those winters. So clearly as rare as these triple dip La Nina’s are, this one is going to be one of kind. Looking back at La Nina winters that had a positive PDO, we come up with 1908-1909, 1938-1939, 1984-1985, 1995-1996 and 2005-2006.

Only 95-96 featured a weak polar vortex and a strong very persistent negative phase of the AO and NAO. That winter was an extremely snowy winter. Due to how the pattern for the entire winter was perfect for winter storms. So that doesn’t mean this winter would end up the same. But, each one of these winters featured average to above average snowfall across our region.

Hunga Tonga Hunga volcano:

In part one I went into some detail on the Hunga Tonga Hunga eruption. But that volcanic eruption is so unique, that it forces me to talk more about it and the impacts it could bring for this winter.

Here are a couple of images that show the amount of Water Vapor from the eruption and its distribution across the globe. We can see that the amount of water vapor released is astonishing. We can also see that the vast majority of the stratospheric water vapor is confined to the Southern Hemisphere.  The amount and distribution are going to have a big say in this winter’s temperature and precipitation pattern. In fact, the eruption aftereffects are the main reason this hurricane season has acted the way it has.

 

It all comes down to balance, or in this case the lack of balance.

In part one I showed the stratospheric cooling at occurred in the Southern Hemisphere. When we go to see the stratospheric data from the CPC and look at the 30hPa layer of the Southern Stratosphere we can see that the current temperature (shown by the red line, is at a historically low level. It is well below the base line. The 50hPa layer shows the same kind of well below average cooling. All of this rapid cooling was a result of all that water vapor being sent into the Southern Hemisphere stratosphere causing the upper atmosphere to contract.  As a result of the upper atmospheric cooling the troposphere ended up warming due to the expansion of the lower atmosphere

But when we look at the stratospheric data for the Northern Hemisphere, we see the exact opposite, those 30hPa and 50hPa layer temperatures are above average.

The Subtropical Jet has been very active this year; which is very atypical for a La Nina year. This is one of the main reasons this year’s hurricane season turned out the way it did. The Northern Hemisphere atmospheric profile was a blend of La Nina and El Nino; which led to all that extra windshear over the tropical Atlantic due to the active subtropical jet. So that well above average hurricane season forecast, never had a chance to get going. This was all a result of the global atmospheric circulation trying to find balance. This is already affecting the polar vortex over the Arctic. In these images we can see while the Polar Vortex over the Antarctic is very strong and well defined. The Polar Vortex over the Arctic is very weak and very elongated.

North 

 

South

Source Earth Null School

As this pattern continues, the Subtropical jet is going to be much more active for the 2022-2023 winter than is typical of a La Nina winter.  With the Polar Jet being active and also having an active Subtropical Jet; there is going to be increased chances for phasing involving the Northern and Southern Jets. How this phasing comes about will be determined by these winters storm tracks.

 

Other important Teleconnections:

The Quasi Biennial Oscillation (QBO):

The QBO deals with the variation in wind flow in the lower stratosphere at the 30hPA layer above the equator. The QBO can influence weather patterns across the globe. This alternating belt of strong stratospheric wind completely changes direction right around every 14 months. So, the full cycle is roughly 28 months. When the winds are westerly (WQBO) the QBO is in its positive phase. So, when they blow in the easterly (EQBO) direction the QBO is in its negative phase.  The QBO has in influence on the strength of the jet stream, polar vortex and the likelihood of high latitude blocking.

During the positive phase winter temperatures across northern New York State into Northern New England are more likely to be colder than average, with the Mid Atlantic and New England likely to be drier than average. During the negative phase the cold shifts south a bit; so Central and Southern New York State, Southern New England, Pennsylvania, and the Middle Atlantic to be cooler than average. During the negative phase the entire Northeast and Northern Middle Atlantic tend to be drier than average.

Here is a look at the QBO composites

 

Source…Philly Weather Authority

Dec – Feb Temperature and Precipitation anomaly probability maps.

Westerly QBO

 

 

Source World Climate Service

Eastern QBO

 

 

Source World Climate Service

Last winter the QBO was negative; currently the QBO is in a positive phase. As of September, the index was at +9.80.

This year has seen the upper atmospheric winds fairly weak. Could this have something to do with the volcanic eruption back in January? Maybe. With this, it should lend some support for high latitude blocking and a decent chance for some stratospheric warming here in the Northern Hemisphere.

 

 

The Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO):

The AO is a northern hemisphere circulation pattern that influences the position of the northern jet stream. It also has some influence on the strength of the polar jet as well as the strength of the Polar Vortex.

During the positive phase the Northeast and Northern Mid Atlantic Region generally see warmer and more moderate winters. During a positive phase of the AO, the Polar Vortex is generally strong.

During the negative phase the Northeast and Northern Mid-Atlantic Region generally see more in the way of cold and stormy winters. During a negative phase of the AO, the Polar Vortex is generally weaker.

The NAO deals with the air pressure pattern between Greenland and the Azores. During the positive phase, the CONUS generally sees a Zonal west-east flow, which typically keeps the cold air bottled up in Canada; this is generally because we see little high latitude blocking during the positive phase of the NAO. 

During the negative phase, we generally see a lot of high latitude blocking over Greenland. The blocking forces the Jet stream to buckle, bringing cold air outbreaks into the Great Lakes and Northeast.

 

 

When we see an east based La Nina, typically we see a predominate negative AO and NAO.

 

 Pacific North American Pattern (PNA):

When the PNA is positive generally in Western Canada and the Western CONUS. it is warmer than average and the Eastern CONUS. is colder than average, there is also a tendency for the eastern CONUS to see below average precipitation as well. When it’s negative, we see the opposite occur more times than not. Currently the PNA is in a positive phase.

 

 

Courtesy of the NWS Climate Prediction Center

Given the overall setup, I favor the idea of the PNA being primarily positive this winter.  

 

Eastern Pacific Oscillation (EPO):

The EPO deals with the atmospheric flow pattern across the Eastern Pacific including Alaska. In other words, the EPO is about the placement of the trough around the Aleutians into the Gulf of Alaska. During a positive EPO the trough is located in the Central and Eastern Gulf of Alaska. As a result, we see strong Pacific jet pushing in a mild north Pacific air flow pattern into the Western CONUS, as this air flows over and down the Eastern slopes of the Rocky Mountains, it warms up and dries out. This typically results in warmer than average temperatures across the Central and Eastern CONUS. During a negative EPO the trough is centered in the Aleutians into the Western Gulf of Alaska. This results in a ridge over the Eastern Pacific off the West Coast. Because of the ridge, the western flow of that mild Pacific air is diverted up toward Alaska.  As Alaska warms, we see the cold Arctic air displaced and forced to move down the western ridge into the Central CONUS. Because of this the Plains and Great Lakes tend to be very cold, some of this cold migrates East into the Northeast and Northern Middle Atlantic.  So typically, our region tends to see colder overall temperatures during a negative EPO.

 

This winter the EPO is going to be the composer, controlling how all these factors mesh. Because the EPO has a major influence on storm tracks across North America.

 

Storm Tracks:

This winter’s storm tracks will be based on the idea of moderate East Based La Nina that will weaken as we get into Midwinter, this along with the pattern setup caused by a positive PDO that interacts with a primarily negative AO and negative NAO and the phase orientation of the EPO during the winter of 2022-2023. This will be enhanced by the results of the Hunga Tonga Volcanic eruption making for a very active subtropical jet, and the increased chances for higher latitude blocking over Greenland due to the QBO. The type of storm and precipitation type will be mainly determined by the phase of the EPO and NAO; these are variable and so we will see a range in outcomes.  

 

When the EPO is positive, the pattern would favor a general storm track into the Great Lakes.  A positive NAO would mean a lot of snow into the Western Great Lakes. We would expect mixing over the interior parts of the Northeast into the Eastern Great Lakes, with a quick change over to rain along the coast. If the NAO is negative, The Northeast would expect to see a substantial mixed precipitation type storm.

When the EPO is negative, the pattern would favor a general snowstorm in the Northeast and Middle Atlantic.  A positive NAO would mean a less chance for phasing between the northern and southern jets, with a general track farther from the coast, this would favor snow for interior New York State and Pennsylvania, leaving the Middle Atlantic and New England more likely a missing out on heavy snow. If the NAO is negative, The Northeast and Middle Atlantic would expect to see a substantial winter storm, due to the high likelihood of both jet streams phasing, with even the potential for a triple phase event. A triple phase storm is when we see the subtropical Jet, the Pacific Jet and the Polar Jet all phase. A true triple phase snowstorm is rare but when they occur, they end up as monster snowstorms.  The pattern this year is going to favor the chance for Miller A and Miller B nor’easters.

Types of winter storms link

Polar Vortex:

As I showed earlier the Polar Vortex has been very disrupted and fairly weak. Now while the Polar Vortex is strengthening as it should be at this time of year. But given the factors I went over; I don’t see the Polar Vortex becoming strong this winter. So it will be easier for the vortex to elongate and split.

 

Analogues:

1908-1909, 1938-1939, 1984-1985, 1990-1991, 1995-1996, 2005-2006, 2010-2011, 2013-2014.

These analogues are based on winters that had a positive PDO with an East based La Nina, had similar SST pattern, and a cool southern hemisphere.

Conclusion:

In part one I discussed how December and January look to be active and wintery. I still believe this to be the case. It is unclear how the end of February into March will act due to the weakening La Nina.

I believe the polar vortex will be weak and will have the potential to be disrupted several times.

The subtropical jet is going to stay active right through the winter, which is something we don’t typically see during a La Nina winter.  

 

Based on the analysis so far, I think this winter will end up colder overall than I indicated it would be in part one. The pattern is looking to be very active with the chance for several cold outbreaks. The pattern should produce several opportunities storm tracks near and offshore, with the idea of prevalent blocking over Greenland due to a general negative NAO, the chance for these storms phasing will be rather high. As for the Lower Great Lakes, this looks to be an active lake effect snow winter.  

Eastern Long Island along the Connecticut Coast into Rhode Island, look to see near average temperatures, and average snowfall.

For Maryland, the major Cities along the I-95 Corridor, Eastern Long Island, Southeastern Massachusetts including Boston will see average to slightly above average snowfall with overall temperatures ending up around average.

For much of the rest of the interior Pennsylvania, New York State and New England, generally below average overall temperatures with snowfall ending up above average.  This is looking to be a good Lake effect snow winter.  

 

Well, that’s it. I will be releasing part three end of November into the first week of December. Part three will cover the overall trend that has been occurring since part two was released, and will attempt to narrow things down a bit more.