Wx4cast: The 2024 and 2025 Northeast Winter Outlook Part Two

Well December is going to be here in a few weeks

So far 2024 has been one of the, if not the warmest years on record.

For the last few years I’ve been releasing the winter outlook in three parts, but for this year, I’m only going to do two parts.

Link to part one.

Getting into the outlook:

The Outlook will generally focus on the end of November into the first part of March.

The last several winters have seen well above average temperatures and below to well below average snowfall. The question is, will this winter break that trend?

As far as snowfall, it will cover first flake to last flake.

Sea Surface Temperatures (SSTs):

Image Credit Tropical Tidbits

Looking at the chart we can see the Equatorial Pacific SST anomalies are below average, between the Dateline and the South America coast. This is showing that an La Niña is trying to form. But currently the ENSO is still considered neutral.

It’s important to point out that the SSTs across the Northern Hemisphere are well above average. This is especially true for the northwest Pacific. We can also see are also above average. There are spots where there are below average SSTs, particularly in the South Pacific.

What’s going on in the Pacific:

I talked about the developing La Nina in part one. But the La Nina is taking longer than I thought it would, but rest assured it will make impacts on winter 2024-2025.

As I said above, we can see the La Nina signature in the eastern into central Pacific.

Once the La Nina is declared it still looks to be a weak to maybe a moderate central Pacific La Nina (modoki)

La Nina Modoki events are very rare, even rarer than El Nino Modoki. We had a La Nina Modoki in 1989. The winter of 2010-2011 was another La Nina Modoki.

Weak and strong La Nina’s produce less snow in and around the Middle Atlantic Region, with the Middle Atlantic Region seeing more snow on average during moderate La Nina's’

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 could see the AO and NAO stay more in the way of positive over winter 2024-2025.

If this does become a La Nina Modoki, it would tend to have the storm track a little farther north than when we see an east based La Nina. This would setup the Northern Mid-Atlantic region as the battle zone. This would mean the Northern Mid Atlantic and those close to it, would see a roller coaster of temperatures fluctuations that could vary from week to week. This could have large implications as to precipitation types during the winter.

An interesting fact is that during La Nina years, December tends to become very active

Image Credit Climate Prediction Center / NCEP

The Oceanic Niño Index (ONI) is based on SST departures from average in the Niño 3.4 region, and is a principal measure for monitoring, assessing, and predicting ENSO.

La Nina is characterized by a negative ONI less than or equal to -0.5ºC in Nino region 3.4.

The JMA model is showing a stronger signal for a moderate La Nina than the others are.

The Southern Oscillation Index (SOI)

The SOI is an index used to indicate the development and intensity of El Nino or La Nina events. This is calculated using the pressure differences between Darwin and Tahiti. These pressure differences effect the strength of the Pacific equatorial trade winds. Negative values favor El Nino, while positive values favor La Nina.

Here are the SOI Values from November 10, 2024

During the summer SOI values showed El Nino as trying to hold on. The monthly SOI value for July 2024 was minus 5.83, very close to the El Nino benchmark. The 30-day running average of the SOI dipped to minus 17.1 on Aug. 3 a strong El Nino signal. And the daily SOI value Aug. 5 was a neutral reading at plus 3.09. September saw the SOI turn more negative. October showed a shift toward La Nina. Since then, the SOI has been wavering a bit. Currently it’s at 4.31.

The IRI plume is predicting a weak and a short duration La Nina, as indicated by the Nino-3.4.

Pacific Decadal Oscillation (PDO)

The PDO is one of the major weather drivers for our overall weather patterns. Looking at the SST anomalies, all y’all can see the cool water off of coastal Alaska. This is showing that Currently the PDO is negative. The PDO has decadal variability negative values were generally observed from around 2000 to the early 2010s, and positive values were generally observed in the late 2010s, the PDO has been negative since around 2020.

The PDO is made up of the Kuroshio Current near the Philippines; this moves through the northwestern Pacific Ocean bringing warm water near Alaska and the West Coast.

This sets up a pattern for strong troughing over the Western US and a ridge in the Eastern US. Historically one of the biggest factors for cold and snow in the Northeast is warm water in the northeast Pacific. When we look at the SST Warm northern Pacific with cooler water along the West Coast from the Gulf of Alaska and down the Coast of California. This is looking to be a strongly negative PDO. So, the PDO is showing a warm signal for the eastern U.S.

Solar

The Solar cycle is generally looking to be at its peak, as is evidenced by all the spectacular Northern Lights displays over the last few months.

When we’re in solar minimums we tend to see much more high latitude blocking than during solar maximums.

The Quasi-Biennial Oscillation (QBO)

The QBO is a band of winds in the upper atmosphere near the equator. The winds generally change direction every year and a half.

The QBO is westerly, meaning it’s positive.

Positive QBO winter can see more high latitude blocking on average.

Some of our snowiest winters have been during a positive QBO

There is a correlation between solar activity and the QBO, when were near maximum and the QBO is westerly, the polar vortex is more likely to be stronger, keeping the cold air more in the way of being lock up in the arctic.

The Indian Ocean:

Image courtesy of Tropical Tidbits

The cooler water in the Eastern and southern Indian Ocean are going to play a factor in the upcoming Winter season. Generally, the places where there are colder SST is where there will be sinking air. The water temperatures in the Indian Ocean are a part of the MJO. That warmer water northwest of Australia will increase the odds for more convection (storms) in the western Pacific closer to the Dateline. This will affect the ridge trough pattern moving forward. This does increase the odd that the SOI will likely stay in the positive numbers for a big part of winter 2024-2025.

Other teleconnections and the Atlantic:

The Atlantic

Image courtesy of Tropical Tidbits

AMO

The AMO is an ongoing series of long-duration changes in the sea surface temperature of the North Atlantic Ocean, with cool and warm phases that may last for 20-50 years. The Warm phase is positive. with the cool phase being negative.

The AMO is positive

This is very apparent when we look at the SST anomalies in the Northern Atlantic.

When the AMO is in its positive phase and the sea surface temperatures are warmer, studies have shown that the main effect in winter is to promote the negative phase of the NAO which leads to "blocking" episodes over the North Atlantic sector, allowing cold weather systems to exist over the eastern US and Europe.

Madden-Julian Oscillation (MJO)

The MJO is a tropical disturbance that transfers wind, precipitation, and pressure changes eastward around the Earth every 30-60 days.

Currently the MJO is in phase one. From here the MJO is going to quickly move into the center null circle, where it will weaken. When it MJO is tracking through the null no phase is favored. Phase one favors troughing in western North America and ridging in eastern North America. So, for the rest of November the MJO won’t exert a lot of influence on the overall U.S pattern.

Once it leaves the null during December, it looks like the MJO will rotate into favorable phases as we approach mid-December, so mid to the end of December could be quite cold.

Artic Oscillation and the North Atlantic Oscillation

The AO and NAO are used to try and track high latitude blocking. The AO refers to opposing atmospheric pressure patterns in the middle and high latitudes. A positive AO means the surface pressure is low over the arctic. A positive AO helps keep the mid latitude jet strong enough to keep most of the arctic air locked to our north. When the AO is negative, there tends to be high pressure over the arctic. As I said above, high pressure in this part of the arctic is called high latitude blocking. It tends to weaken the zonal flow, resulting in greater occurrences of arctic air intrusions into the Northeast CONUS.

NAO

A negative NAO generally isn’t about pulling cold air down from the north, instead what it does do is lock those colder temperatures in. The NAO helps enhance what is going on in the Pacific Basin. Overall, a negative NAO sets up high latitude blocking near Canada and Greenland, which slows down storms, allowing them to become stronger. It also helps promote a stormier pattern here in the Northeast.

Some years see the AO index not bounce around so much; when it stays persistently negative during October the AO is generally more negative during the winter season. During this October the AO and NAO have been going back and forth. When they act like this it sends a mixed signal when it comes to cold outbreaks and high latitude blocking for this winter.

Northern Hemisphere Snowpack:

Snow cover is in white

from 30 September to 22 October

Graphics courtesy NOAA/NOHRSC

Snow cover is in white

Here is a current look at snow cover

Graphics courtesy NOAA/NOHRSC

Judah Cohen has done research that correlates this to below average temperatures over the eastern US and above average snowfall over the Northeast into Mid-Atlantic Region. If the snow pack below 60◦ North is above average and expanding during October into November, there is an increased risk for high latitude blocking the following winter. Right now, snow cover in that part of Eurasia is higher than in many recent years…. So, it’s a good sign for snow lovers.

During October the Eurasia snow cover extent across Eurasia grew quickly. But when we got closer to the end of October snow growth slowed way down. Now the snow extent is lower than average for this time of year. The black dashed line represents the mean value using October 2009 through 2023.

The snow extent has increased across Alaska and northwestern Canada. Right now, the snow extent is sending mixed signals as far as winter cold goes. But as it continues to grow, it will be a source of colder air, that could get tapped into from time to time, bringing colder air masses into the northern Plains, Upper Midwest and the Great Lakes. Some of that cold air could expand across the Northeast at times.

When the snow extent is greater across Eurasia (especially across Siberia) in October it is a sign that the polar vortex (PV) is likely to be weaker on average, which could signal higher odds of cold air outbreaks in the eastern U.S.

Analogues:

For the analogues I came up with, I used a combination of weak La Ninas, and some La Nina years that followed a El Nino. I also included tropical years that had tracks like we saw this year.

Tropical seasons

Tropical seasons in the Atlantic that see late season activity tend to start off cooler in the eastern U.S. When we look back at similar seasons, we generally saw two predominate corridors one in the western into central Atlantic. The 2^nd had several tropical cyclones tracking through the Gulf into the Southeast US activity tend to see colder first halves of winter.

Hurricane analogues

1950, 1985 1995, 2000, 2005, 2010, 2020, 2022

Many of these were snowy and colder overall.

Winter 2022 -2023 wasn’t a great winter in spite of 2022’s Hurricane Ian

2022 saw an early shot of cold air, but it didn’t stick around and most of the rest of the winter was warmer than average.

Both 1995 and 2010 were decent winters.

La Nina’s that followed El Nino’s

1966-1967, 2005-2006, 2007-2008, 2013-2014, and 2020-2021

These winters we’re generally warmer with above average temperatures across the Northeast into Middle Atlantic region.

The years I’ve settled on

1985,1986, 1995-1996, 2005-2006, 2007-2008, 2010-2011. 2013-2014, 2016-2017, and 2022-2023

When dealing with analogues, any one of them can show up during the winter.

When we average out these analogue years, we see this general look.

Temperature.

Image Credit Physical Sciences Laboratory NOAA/NCEI

Precipitation

Image Credit Physical Sciences Laboratory NOAA/NCEI

The winter temperature and precipitation pattern:

When looking at all the factors, my general thoughts on the temperature and precipitation pattern this winter are still looking sound.

La Nina generally pushes the polar jet stream farther north and causes chillier conditions in the north central U.S, Great Lakes, and Northeast.

I have a lower confidence level in the overall pattern this winter. So I’m sticking to the general zones I established in Part one. December could end cold, this general idea of cold could stick around for at a large part of January. But I do feel winter could start to wind down middle to end of February.

Wintertime temperatures will end up varying greatly north to south during the winter. Wintertime Precipitation will tend to be a bit snowier across northern parts of the region, while southern parts of the region will be dealing with greater chances for mix and rain events.

Here is the zone map

Zone one…

Those of y’all in zone one, will see overall slightly below average temperatures during December into February. As far as general precipitation it should end up being wetter than average. With the cooler temperatures snowfall should end up slightly above average to above average as well.

Lake Effect Snow

The Great Lakes are near or at record water temperatures.

These water temperatures will increase the odds for significant lake snow events during the first part of the winter. So, the typical snowbelts should end up with overall above average to well above average snowfall for the season.

This doesn’t mean there won’t be warm periods. As I said above, this winter is going to end up being highly variable.

Zone two…

This zone looks to see overall near average temperatures, along with average general precipitation. There will be an issue with mix events during the winter. As far as snowfall that looks to be overall average to slightly above average.

Zone three…

This zone looks to see overall average temperatures to slightly above average, along with average general precipitation. There will be an issue with mix events during the winter. So, expect to see many events start out as a mix then switch over to snow, or starting out as snow and changing to a mix. But there will be a chance for pure snow events. As far as snowfall that looks to be overall average to slightly below average.

Storms will end up being very hit and miss.

Zone four…

This zone looks to see overall Temperatures above average with precipitation near average. Snowfall accumulations will be below to well below average, when everything is said and done. Unless a storm tracks just right, I don’t except to see much in the way of snow. some of your storms will be a mix. But generally, many of them could be all-rain events. It is possible some places in zone four, won’t see any snow this winter.

Summing it up:

A couple of wild cards this winter will be, the MJO and the Polar Vortex.

The teleconnections are at odds with each other, with a lot of arguing going on! But the general idea is teleconnections point to the warm side of things on average.

MJO is going to be fighting with the other teleconnections. With the mixed teleconnection signals, the PV is another wild card.

Could see some very cool weather toward the end of November. December could be quite active and wintery. From Mid December to beginning of January it looks to be quite cold.

The pattern is going to go back and forth between cold and warmth.

What ends up happening will depend on week-to-week variability between the MJO and teleconnections like the AO and NAO.

Overall, the warmth should outdo the cold on average.

Winter could start to winddown during February into early March.

Winter of 21-22 could show up, which would mean a better chance for a snowier winter overall.

As I said in part one, in the Northeast most of our snowier winters ended up occurring during weak to slightly moderate La Nina's’ The Middle Atlantic on the other hand tend to see less snow.

There is a lot of uncertainty for this winter, with the overall pattern featuring a lot of back and forth.

So northern parts of the region should see some cold and snow, while the Middle Atlantic and I-95 look to see a warmer winter and maybe little in the way of snow. Most of it will come down to how the MJO tracks through its phases and on how the AO and NAO behave.

Well, that’s it for this year’s winter outlook.

I want to take time to thank you for reading my thoughts on winter 20249-2025. If you have questions not covered in this outlook, or general questions about the upcoming winter please don’t be afraid to ask.