2023 2024 winter outlook part two

 

Part two will cover what this year’s tropical activity can tell us, snow cover in Siberia, and talk about some of the teleconnections like the Pacific Decadal Oscillation.

To read part one follow this link

I've been working on this and trying to figure out the best way to present it in the most concise straightforward and easy to understand format. Which is far from an easy task. 

I’ve tried to take a balanced approach to what I’m seeing this year. Remember a winter outlook is an overview of what the entire winter season should feature. This outlook isn’t going to cover storm details on snow amounts or track, it will feature a broad overlook of the general pattern we will likely see at times during this winter.

 

Sea Surface Temperature (SST) anomalies…

 

Teleconnections:

Our atmosphere is very fluid. These fluid properties are constantly changing over time and location. What’s going on over one part of the Planet has a downstream impact somewhere else.  A deepening ridge, means a trough must dig.  The weather patterns in other parts of the world are called teleconnections.

During the winter, changes in the phases of certain teleconnections can produce conditions favorable for a cold and snowy pattern in the Northeast and Mid-Atlantic Region. Besides the El Nino Southern Oscillation (ENSO) the other teleconnections we generally look at are the Artic Oscillation (AO), Eastern Pacific Oscillation (EPO), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Pacific-North American Pattern (PNA).

 

The El Nino Southern Oscillation (ENSO)…

One of the winter major forecast factors to look at in the late fall/winter is the state of the ENSO. The ENSO is a fluctuating weather pattern around the equator in the Pacific. The cool negative phase is called La Nina where we see cooler than average sea-surface temperatures equatorial Pacific, the warm positive phase is called El Nino where we see warmer than average sea-surface temperatures in the equatorial Pacific.  Part, one talks about how this years ENSO and the developing El Nino are shaping up.    

 

El Nino

A lot of people including many meteorologists are placing a lot of importance on this El Nino and how it may be a Super El Nino. But while a moderate to strong El Nino is likely; we could fall short of super El Nino status.  

This isn’t going to be a normal El Nino

Strong El Nino’s  1957-58,1965-66,1973-74,82-83,1991-92,1997-98,2009-10,-2015-16

During El Nino we typically see a less-active, west-to-east storm track across the northern US. The subtropical Jet stream is also typically quite active.

Why was the Atlantic tropical season so active?

We had recorded warm water.

But the shear didn’t tear them apart as much

Could it be due to the placement of that shear?

The warm water in the Indian Ocean (a positive IOD) is one major reason. Another reason is the record warmth in the Atlantic Basin.

So, we got a lot of convection (rising air) around Africa and a lot of subsidence (sinking air) around the South Pacific Islands, that helps displace a lot of the lifting. So, we had rising air near and around Africa and lifting air over the Eastern into Central Atlantic. But we had sinking air in the Caribbean and Gulf of Mexico, so we didn't see much development in a large part of the Caribbean and GOM. The warm Atlantic overruled El Nino conditions.  

Typically, South America is very wet during an El Nino. But this year South America is experiencing major drought

So, it looks like the warm water around the Equatorial regions, shifted El Nino’s influence east, resulting in a very active 2023 hurricane season.

  

 We also have to look at the northern Pacific…

 

The Pacific Decadal Oscillation (PDO)

 The PDO deals with sea surface temperature anomalies over the Northern Pacific (north of 20° north latitude), as with all teleconnections it has a positive and negative phase. These phases typically last for decades. The PDO represents the oceans response to the atmosphere.  In this way it is a prime driver for low pressure systems in the north Pacific, for example the Aleutian low-pressure system in the Gulf of Alaska. Depending on how strong this low is, it will have a different impact on wind flow, and the pressure gradient. If the Aleutian Low is very strong, we tend to see a stronger southernly flow along the immediate West Coast.

The positive phase is characterized by cool SSTs north of Hawaii and warmer than average SSTs in the Gulf of Alaska and along the West Coast of North America. The negative phase we see the opposite, warmer than average SSTs north of Hawaii and cooler than average SSTs in the Gulf of Alaska and along the West Coast of North America.

During the positive phase the Mid-Atlantic and Northeast is more likely to experience overall below average temperatures for December, January and February. During the negative phase the opposite is true, with the Mid-Atlantic and Northeast likely to experience overall above average temperatures for December, January and February.

The PDO has been negative for the last several winters. But the last couple of months has seeing it quickly moving towards neutral after being negative for the last four straight years. The last time this setup occurred was during the Fall of 2002. The winter that followed was a very decent winter snow wise here in the Northeast.

So, while this is theoretically a negative PDO. it really isn’t a textbook negative PDO. During a typical negative PDO the water is much colder in the Gulf of Alaska and west coast of Alaska, the cold water would also typically extend down into the Pacific Northwest. So, while the water is cooler it isn’t as cold as you would expect to see during a negative PDO.

The PDO and the Pacific North American Pattern (PNA)

There is a direct correlation link between the PDO and the PNA. During the winter the correlation is greater than 0.80.

The PNA is closely related to the strength of the Aleutian Low and the strength of the PDO

The PNA for our purposes here, is the PNA is the main driver of the trough ridge pattern over North America

During a negative PNA there typically is more overall upper level troughing over the western U.S leading to cooler and wetter conditions, while the eastern U.S. is more likely to see overall ridging leading to drier and warmer conditions. During a positive PNA the eastern U.S. sees more in the way of troughing while the western U.S. sees more in the way of ridging.   

 

Last winter, we had a negative PDO and a negative PNA during January and February that combination resulted in very warm temperatures across the Northeast and Mid-Atlantic Region.

 

The PDO and the ENSO

During El Nino, the Aleutian Low is generally stronger than average during the winter months; this favors a positive PDO pattern. The opposite is true during La Nina; the Aleutian Low is generally weaker than average during the winter months, which favors a negative PDO pattern.

A negative PDO favors a weaker El Nino or a stronger La Nina. A positive PDO favors a stronger and longer lasting El Nino or a weaker La Nina

This is going to be at least a moderate El Nino winter, with a strong likelihood of the El Nino being strong. So, since this isn’t a La Nina year. There is a strong signal that this winter will feature a positive PDO. What we’re seeing in the SSTs in the northern Pacific supports this idea, of a developing positive PDO.

 

When the PDO and the PNA are in opposite phases, they are working against each other (Destructive interference)

 

As I said above, the other major teleconnections we look at during the winter are the AO, EPO, and the NAO. Unlike the ENSO PDO and to a lesser extent the PNA; these three have a tendency to fluctuate between phases every couple of weeks or so.   

 

Artic Oscillation (AO)

The AO deals with the strength of the Polar Vortex (PV) and determines whether or not there will be a supply of Arctic air available to fuel winter weather. I will explain more about the PV when I discuss the current snow cover. But, a positive AO indicates that the PV will be strong and Arctic air will stay locked up near the pole while a negative AO indicates the potential for a weaker PV leading to the chance for Arctic air to escape southward.

Eastern Pacific Oscillation (EPO)

During the winter, the state of the EPO controls whether there is, a cross-polar path for very cold Arctic and Siberian air to flow across the pole and down into central and eastern North America.  During a negative EPO, a ridge builds over Alaska. The more amplified this ridge is, the greater the chance for cross-polar flow. Conversely, a positive EPO indicates a large, persistent low in the Gulf of Alaska and results in warmer weather for the lower 48.

 

 

North Atlantic Oscillation (NAO)

The NAO, in its negative state, indicates high-latitude blocking over Greenland. This lingering area of high pressure causes the flow to stagnate. The storm track is often underneath it and can result in persistent storminess for the Eastern US. On the contrary, a positive NAO has no such block and the storm track moves quickly across the CONUS and out into the Atlantic.

Can the eastern US still get winter weather with a positive NAO? Yes, but they’re often quick-hitters and rarely significant events.

The ideal configuration for a period of winter weather in the eastern US is a negative NAO, negative AO, negative EPO, positive PDO and a positive PNA. Can other combinations still produce winter weather? Sure, but this combination is almost a guarantee.

 

Snow cover:

Since it is still October, I remain focused on the snow cover advance across Siberia and what impact it may have on the stratospheric polar vortex (PV).  I am sure I will be discussing this pathway more in the coming months.  More extensive snow cover across Eurasia in October, and this mostly confined to Siberia, the more likely the PV will be weaker than normal during the winter months that favors widespread colder temperatures across the Northern Hemisphere (NH) but in particular in East Asia and the US east of the Rockies.

The more widespread snow cover is across Siberia during October, the more we’re likely to see a weaker than average stratospheric Polar Vortex (PV) during December through February. The PV is a large area of low pressure that sits over the Pole during the winter. When snow cover in Siberia is above average, it favors the negative phase of the Arctic Oscillation (AO).  When the Arctic Oscillation is in its positive phase, the jet stream, which brings us  a large part of our weather in middle latitudes, tends to shift to the north. So, when the AO is positive, the polar vortex is generally strong and in a tight circle, with cold air bottled up over the Arctic. When the AO is negative, the PV tends to be weak and much wavier meaning it is prone to collapse, this increases the likelihood of cold outbreaks here in the U.S. east of the Rockies.  

So far this year, snow cover over Siberia has been well below average, but over the last couple of weeks this departure has been reversing. Snow cover over northern Canada isn’t really seeing any big improvement in snow cover. But in general, the larger the snow cover extent in Asia and Canada in the Fall, the better the chances for stronger polar air outbreaks during the winter.

 

We will have to keep an eye on this; as there is still time for the snow cover over Canada and Eurasia to increase.  

 

Here is what I’m thinking based on how things look to be trending….

Right now, the closest the atmospheric setup and pattern resemble is the winters of 2002-2003 and 2009-2010. Those winters saw generally colder temperatures and some snowy periods

I do think we’re going to have a predominate positive PDO and positive PNA. This would allow for the potential for cooler overall temperatures for the winter of 2023-2024 here in the Northeast and Middle Atlantic. But storm tracks and temperatures will depend on the phases of the AO, NAO and EPO.

Real winter will be slow to start, with overall temperatures in December running average to slightly above average. January will see generally average overall temperatures. Then February into March will see overall temperatures below average.  This isn’t going to be the coldest winter on record; but it also won’t be the warmest winter on record. Those predicting a torch for the entire winter are likely on the wrong side of what looks to transpire.

There will be blocking setting up near Greenland at times. Depending on how the polar vortex acts during those times will determine the amount of cold that will be available.  

We’ve already had some early season nor’easters. I think the winter is going to feature a few nor’easters that come up the Coast from the Gulf of Mexico (Miller A nor’easters) and some storms that move into the Ohio Valley that then transfer to the Middle Atlantic Coast (Miller B nor’easters). The tracks will depend on the alinement of the teleconnections, if we have a negative AO along with a negative west-based NAO, it would favor a snowstorm bringing the chance meaningful snow for parts of the region. But if the negative NAO is east-based, the storms would likely form too far east to bring much in the way of snow to parts of the region.  How much cold these storms have will depend on the phase of the EPO, if the timing works out, then a negative EPO would bring the opportunity for at least a moderate polar airmass over the region.  

The amount of snow this winter will be very dependent on your location. Those in western parts of our region, will likely see overall snow amounts that are average to below average, with central and northern parts of the region ending up generally with overall average seasonal snow amounts. Those in the Middle Atlantic into southern New England, will have the greatest chance of seeing overall above average seasonal snow totals.  The winter pattern that looks to be setting up will likely see at least one to two big nor’easter events from mid-January, February into early March.  These storms would have the potential to bring major snowfall across the Middle Atlantic, I-95 Corridor into Southern New England. We’ve seen these kinds of winters before, where one or two big storms made up the bulk of the winter snow.   

 

Well that’s it for now.

Part three can be found here

2023 2024 Winter outlook part one

 

Well, we’re at that time of year, where thoughts about the upcoming winter start to surface. A professor of mine once said “global weather is local weather”.  By that they meant that the local weather we experience day in and day out is just part of the overall global weather pattern. This is the basic principle of weather forecasting.  The weather locally doesn’t occur at random. It is the result of all the large and small interactions between global teleconnections and all the unique factors that make up our local environment.  My weather outlooks are based on scientific principles and processes; that I try to interpret; in order to figure out how these influences will work together, for an overall picture on what we can expect here in the Northeast and Northern Middle Atlantic.   Over the last few years these seasonal outlooks have been multi-part. This is necessary due to the shear complex nature of the data. So, here is part one of my 2023 and 2024 winter outlook.  

Remember an outlook is a general blueprint; it’s not a perfect layout as to what will happen over the Winter season.  

Some of the major influences this winter are going to be El Nino, Stratospheric Polar Vortex and Teleconnections like the Quasi-Biennial Oscillation.

Part one of the outlook, will focus on these major influences in detail including the historic implications. I will also show how all of these things intertwine and what they could be hinting at for this coming winter.

If you don't want to read why I'm coming to the conclusion that I am, you can drop to the bottom of the page to read the summation. 

Sea Surface Temperatures:

 

Looking at the SST map, we can see the vast majority of the ocean water in the Northern Hemisphere is very warm. The northern into Central Pacific has this warm spot.  Typically, during an El Nino, you want this area to be cooler.  Also, typically we want the western Indian Ocean to be wet and the area around Southeast Asia to be dry.

The gradient caused by these SST is going to be a big factor as well when it comes to storm development.  

Teleconnections:

El Nino Southern Oscillation (ENSO)…

The ENSO involves Sea Surface Temperature anomalies across the equatorial Pacific. Like all teleconnections, the ENSO consist of a warm phase (La Nina), a neutral phase, and a warm phase (El Nino).  The last three winters were influenced by La Nina It started in September 2020 and lasted into early spring of this year, making it a rare triple dip La Nina. From 2021 into 2023 the La Nina event was the strongest on record.  El Nino was declared back in June. It has been strengthening all summer.

There has been a lot of speculative talk about the implications of El Nino for our upcoming winter; Some saying it will be a torch and others saying it could be cold, some say it will mean a snowless winter. While these predictions are possible, that doesn’t mean other outcomes won’t happen.

It’s important to remember that El Nino’s are not all the same. The region can see different outcomes depending on the placement of where the El Nino is centered. Also, El Nino isn’t the only factor when it comes to the wintertime pattern.

El Nino…

All of the latest weekly Nino indices are in excess of +1.0ºC: Nino-4 is +1.1ºC, Nino-3.4 was +1.6ºC, Nino-3 was +2.2ºC, and Nino1+2 was +2.9ºC.

The most recent IRI plume indicates El Nino will persist through the Northern Hemisphere winter 2023-2024.

This year’s El Nino was declared in June. Since Nature is always trying to find a balance, it should be no surprise that this El Nino is going to be strong, in fact it could end up being a Super El Nino.  I wrote a post on Super El Nino’s which you can find here.

Recent winters have been warmer than average.  When looking back at northeastern United States winters 30-50 years ago, it’s clear that Winters in the past, were generally snowier and colder in the past. While part of that reason has to do with things like the Artic Oscillation, jet stream placement, and many other things; there is no doubt, that a warming planet also playing a part. We can disagree on the reasons for the warming, but we can’t deny the planet is warming.  Super El Nino’s do seem to set a new plateau when it comes to the warming.

Above is an image that Joe Bastardi posted that shows this correlation. So, if the current El Nino ends up being a super El Nino, it will be interesting to see if it sets a new plateau.      

As I said each El Nino is different, but there are a few general patterns that are associated with them. The polar jet stream is typically farther north than average, with the subtropical jet stream sitting across the southern U.S. The subtropical jet is amplified and stays active bringing wet and stormy weather to the South and Southeast. During El Nino the Southeast U.S. is typically colder. At the same time the northern tier of the U.S. is typically warmer than average, due to the placement of strong low-pressure area in the North Pacific.  The Midwest and Great Lakes are characteristically drier than average, many times this dryness extends into western New York State and western Pennsylvania. While the eastern seaboard a storm track that has coastal storms off the Southeast Coast move up the Coast.  In general, New England winters during an traditional El Nino tend to be warmer While the Middle Atlantic region usually is a bit colder and wetter than average. Historically, strong El Nino's have had big impacts on the Northeast, but the correlation is weak. Generally, a large part of the region sees above average precipitation. But as for snowfall Interior New England tends to see lower snow totals, as does western Pennsylvania, and the snowbelts off of Lake Erie and Lake Ontario. While the Middle Atlantic into southern New England tend to see average to above average snowfall.  A lot will depend on exactly where the El Nino sets up.

Here is a diagram that shows a general idea of an El Nino pattern.

 

A so called traditional El Nino, is where the warmest SST anomalies are in the eastern part of the equatorial Pacific Ocean, in Contrast an El Nino Modoki event is where the warmest SST occurs farther to the west in the central Pacific Ocean near the International Date Line. Historically, strong El Nino Modoki years tend to see more ridging of the polar jet stream over the western United States and troughing over the east coast, which can favor cooler weather Northeast. There can also be quite a bit of jet stream variability during an Modoki. The Southeast tends to see much cooler and wetter conditions.  This is because the pattern of the subtropical jet stream resulting in a change in the general track for winter storms.

The models:

The European Center for Medium Range Forecast (ECMWF)

Shows a general east based El Nino for December. But it shows an Modoki El Nino for January into March.

 

The North American Multi-Model Ensemble (NMME) model is also showing a Modoki El Nino for the 2^nd half of winter.

 

 

The models are generally the opposite of what they were showing this time last year. 

 

Quasi-Biennial Oscillation (QBO)

The QBO deals with strong stratospheric winds over the equator. It has two phases a westerly (positive)phase and an easterly (negative) phase.  The two phases switch back and forth in a fairly regular 14-month cycle, so an entire cycle is about 28 months. 

Here is a graph that shows the zonal wind anomalies, going back 4 decades, showing the clockwork phase change.  These winds in the stratosphere descend down to the jet stream where than can either reinforce or oppose the polar jet stream.

Last year we were in a westerly QBO, But the current data shows the QBO is in an easterly phase, the QBO will stay in this negative phase all winter.  Here is a diagram showing the wind direction at 40-10 mb (roughly 66,000 to 84,000 feet).

 

The data shows that The QBO was in a westerly phase last winter. As the winds descend out of the Stratosphere they will have a big impact on how this winter behaves.

The QBO influences the strength of the Polar Vortex so it can have wide ranging impacts and can affect weather in the Middle Latitude through indirect influence on surface pressure patterns.  I will comeback to the QBO; but first I want to talk about the Polar Vortex, as the QBO and Polar Vortex are strongly integrated with each other.

  

The Polar Vortex (PV):

The Atmosphere is composed of many layers; the closest to the surface where we live is called the troposphere. The troposphere is where all the weather events occur. The one above the troposphere is called the Stratosphere.  The Polar Vortex is the result of a large-scale low pressure cyclonic circulation over the North and South Poles. For this post, I will focus on the Northern Hemisphere.  The PV It is connected through all atmospheric levels. But when talking about the PV we tend to break it down to an upper part and a lower part. The upper part involves the Stratosphere and the lower part involves the troposphere.

Here is a diagram that shows the two parts of the PV.  

 

The upper part has an altitude of around 14 miles, so it isn’t impacted by the surface terrain and weather processes present in the lower atmosphere; so, it is more circular and uniform. The lower part is much more uneven in appearance, due to the influence of weather subsystems and terrain.

Depending on the strength of the PV circulation, there can be cold outbreaks in the middle latitudes, where most of us live.  Typically, when the Polar Vortex is strong, the strong jet tends to bottle up the cold air up over the Arctic Circle, leaving the milder conditions in the middle latitudes in places like the United States and Europe.  On the other hand, a weak PV leads to a weak jet, which allows the arctic cold to push south into the Asia, United States and Europe.

Strong is the more common state of the polar vortex.

 

Looking back at the QBO

Here is another chart showing the QBO, the upper right corner is the developing easterly phase. This is going to slowly descend from the stratosphere into the troposphere, where it will have an impact on winter temperatures. As it will work to modify how the El Nino is interacting with the PV.

When the QBO is in a westerly phase, the odds increase for a stronger PV. As I stated above a strong PV increases the odds for a milder winter.

When the QBO is in an easterly phase, the opposite occurs, we tend to see a weaker PV, increasing the odds for a colder winter.

During winters with a negative QBO, those easterlies migrating downward can weaken the jet stream, giving us a better shot at cold air outbreaks; as they help produce warmer temperatures in the polar stratosphere. This increases the odds for Sudden Stratospheric Warming (SSW) events. An SSW is a very rapid warming in the Stratosphere over both poles. It is one of the most extreme changes of weather on the entire planet.  In the space of a week arctic temperatures at the pole between 10 km and 50 km can increase by more than 90 ⁰F.   This causes the PV to wobble. As this process the result of this, pushes the PV away from the Poles, forcing warmer air in the mid latitudes to move north to replace the colder that has been displaced, and as the air moves downward into the troposphere the polar region warms allowing the colder air to work its way into the lower elevations.  During a negative QBO there is a greater signal for high pressure to setup in the North Atlantic, resulting in high latitude blocking over Greenland and eastern Canada, that slows down and can even stall storm systems as they move eastward over the CONUS.

Below is a diagram that shows there is a greater tendency for overall colder winters over the southern and eastern United States and northern Europe during a negative QBO phase.  Of course, there are other teleconnection influences that can also have an impact on overall winter temperatures.  

 

Analogue years:

The key is picking the right analogues

So, the analogues I going with right now are

1958, 1966, 1987, 1995, 2003, 2010

 

Temperature.

Precipitation.

 

The Climate Prediction Center (CPC) released there 2023-2024 winter outlook on September 21.

Temperature Outlook

 

The Climate Prediction Center (CPC) is forecasting above-normal temperatures across the northern United States through the winter months with the best chance for the warmer-than-normal winter to occur in the Northeast and the Pacific Northwest.

Precipitation Outlook

 

The CPC is forecasting drier-than-normal conditions for much of the northern United States. In particular, the Pacific Northwest and the Midwest have the best chance for drier than normal winter months. While the North experiences a drier-than-normal winter, the majority of the South looks to see a wetter-than-normal winter.

I’m not as sure about this winter as the CPC, as I see something that could be a bit different.

What all of this is hinting at:

On average a large part of the Northeast sees a slightly warmer than average winter from an east based El Nino.  The frequent storms moving west to east across the country carry warm air with them, increasing the odds for mixed precipitation events including snow, sleet, freezing rain and plain rain.

But this winter is looking to be quite a bit different from last winter, the things I showed show there is a trend developing that could signal an overall colder winter for 2023-2024.

Historically, strong El Nino Modoki years tend to see more ridging of the polar jet stream over the western United States and troughing over the east coast, which can favor cooler weather here in the Northeast. There can also be quite a bit of jet stream variability during an Modoki.

Everything I’m seeing right now, is telling me this is likely be a hybrid El Nino Modoki event for this upcoming winter. 

El Nino’s typically feature a strong jet stream across the south which carries stormy, cool conditions from Southern California to the Southeast. The subtropical jet data is hinting at a powerful subtropical Jet, that will setup for January February and March. With this there is a good chance for this to be a stormy winter for the East Coast.

Generally it looks like the Winter of 2023/2024 might be off to a slower start across the central and eastern United States. But current data indicate colder temperatures and more snowfall potential in the mid and late part of Winter across the central and eastern United States. The ECMWF and MMME both support the idea of a powerful subtropical Jet for January, February and March. The temperature gradient and the pressure gradient suggest we could have storms spinning up into Nor’easters that run right into New England. 

Many times, so called, monster winters typically have a couple of very big snowstorms, along with many smaller storms.

This is looking to be an above average snowfall winter for the Middle Atlantic into Southern New England. For Most of Pennsylvania New York State, and Northern and Central New England total snow amounts would be around average, with western Pennsylvania, western New York State and the lake effect snowbelts generally seeing slightly below average snowfall.   .

 

That’s it for part one. It’s too early to know more details, but we will see how this trend goes.  I will release part two most likely end of October or the first part of November.

Part two will cover what this year’s tropical activity can tell us, snow cover in Siberia, solar activity, and the Pacific Decadal Oscillation. then part three will release end of November into the first part of December.

Part two can be found here.