Wx4cast: At first blush, here are my first thoughts about winter 2020-2021.

Summer 2020 was very warm and overall, quite dry. But the days are getting shorter, with the sun setting earlier and earlier. We’ve been dealing with cooler temperatures bringing frost/freeze conditions to parts of our region. So, we know lasting cold isn’t all that far away.

I’ve been fielding more than a few questions, asking what I think the upcoming winter will be like. While it’s too early to go into a lot of detail. I can still go over what some of the indices look like and what they’re implying.

First, I will go over what NOAA is thinking.

Here are the outlook maps showing both NOAA’s temperature predictions as well as their precipitation predictions for the 2020 – 2021 winter.

NOAA is predicting above-average temperatures this winter across the Mid Atlantic, Pennsylvania, and most of New York State, with well above average temperatures for New England into eastern New York State.

NOAA is predicting even chances for average snowfall this winter across the Northeast and Mid-Atlantic Region.

What things am I looking at?

Patterns such as LA Nina, Quasi Biennial Oscillation (QBO), Sea Surface Temperature (SST) in the northern Pacific and in the western Atlantic, Solar Activity, Snow and Ice Extent, as well as a few other things offer some clues for the winter ahead.

Sea Surface Temperature (SST):

Surface

Here is a look at global SST anomalies curtesy of NOAA’s Coral Reef Watch.

Subsurface

Subsurface temperature anomalies continue to strengthen. Here are graphics from CPC/NCEP/NOAA, that show the strengthen trend over the last couple of months.

Northeast Pacific Ocean Heatwave:

The warm SST in the northern especially northeast Pacific, will play a major role in our upcoming winter pattern. The well above average warm spot (Blob) in the Northeast Pacific, south of Alaska and off the Northwest Coast of the CONUS, has pulled west a bit, this will allow for ridging to develop over the western part of North America. The Blob that formed between 2013 and 2016 helped bring about very warm winters.

The location of the warm spot should encourage more in the way of a positive Arctic Oscillation (AO)

Teleconnections:

El Nino Southern Oscillation (ENSO):

We’re in a La Nina

Looking at the ENSO regions in the equatorial Pacific we can see that all the regions are colder than average. The warmest region is Nina region 3.4 and region 4. This most likely means this La Nina will be a central based (Modoki). On average we tend to see snowier La Nina’s during weak Modoki years, than we do during a traditional La Nina. This setup would indicate a predominate trough over the Western CONUS, with more in the way of ridging over the Eastern CONUS, during winter 2020-2021.

Generally during La Nina, the Pacific Jet is more varied. Here is a look at the typical storm tracks during La Nina. As far as Nor’easters, La Nina’s tend to see primary lows track out of the southern central Plains through the Great Lakes, with a secondary low developing off the Mid-Atlantic and or New England Coast.

If the La Nina stays weak to moderate, there is still hope of some snow in the Northeast.

If the La Nina becomes moderate to strong snowfall chances will be dismal.

Here is a look at the general temperature difference between a weak La Nina and a moderate to strong La Nina.

During La Nina we tend to see a stronger and colder Polar Vortex on average. This increases the likelihood of a warmish winter; because a stronger vortex is harder to dislodge which helps keep that arctic air bottled up near the North Pole.

Quasi Biennial Oscillation (QBO):

The QBO is an alternating easterly and westerly wind cycle in the lower stratosphere over the equator. A phase typically last around two years.

The QBO is currently transitioning from an easterly (negative) phase to a westerly (positive) phase; the western trend will continue for winter 2020 -2021. This will increase the odds for a warmer winter in the Northeast. During a positive QBO we generally see a strong Polar Vortex and lower chances for sudden stratospheric warmings. The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) are much more likely to be generally positive with the QBO is in its westerly phase. With the NAO and AO likely to be mostly positive it would indicate that high latitude atmospheric blocking in the North Atlantic near Greenland will be harder to achieve.

The Madden Julian Oscillation (MJO):

The MJO is an oscillation that occurs in the tropics. The MJO propagates eastward, as it moves it augments convection (thunderstorms) and precipitation in parts of the tropics; while at the same time diminishing convection and precipitation in other parts of the tropics. The MJO phases teleconnect to certain weather patterns over the United States.

The MJO has primarily been in the Indian Ocean; which is phases 1-3. When in phases 1-3 tropical forcing favorers the East Coast. But the MJO has been trending toward more of a Maritime Continent base state; which is phases 3-6.

Currently the MJO is just outside the NULL (AKA the circle of death) in phase 5. When starting a La Nina we generally don’t see a lot of MJO activity deep into the Pacific. So, the idea of the MJO not having much amplitude is more or less expected. But as the La Nina peaks during this winter, the MJO should have more amplitude.

The MJO most likely will cycle predominately through phases 3,4, and 5 this winter. Typically, these phases don’t support a lot of widespread cold and snowfall across the Eastern U.S. Last winter we saw a good example of what can happen when the MJO stays in the warm phases.

Analogies:

The Analog years I’m looking at are: 1839 -1840, 1845-1846, 1852-1853, 1975-1976, 1984-1985 1998-1999, 2010-2011, 2011-2012, 2012-2013 2016-2017 2017-2018 2018-2019 2019-2020.

For now, I’ve decided on 1975-1976, 1984-1985, 1998-1999, 2010-2011, 2012-2013, 2017-2018, 2018-2019, 2019-2020.

The closest matches to the current pattern are 2010-2011 and 2016-2017. Both of these seasons featured a developing La Nina with a westward trending QBO.

Northern Hemisphere Arctic Sea Ice and snow extent:

Looking at the data from the National Snow and Ice data center. On the ice extent chart, we see we’re at the seasonal minimum. Typically, we see the annual season minimum ice extent mid to last September. On the map, yellow is showing sea ice coverage, white is showing snow cover.

Arctic sea ice is at the second lowest minimum in recorded history. While Ice extent is lower closer to Russia. There is quite a bit of ice cover over Greenland. During the summer melt season, northeast and southwest parts of Greenland saw well above average melting compared to the 1981-2010 average, but below the levels seen in many previous summers over the past 10 years. The melt extent over the southeast and northwest is lower than average.

Eurasian snow cover hasn't changed greatly over the past week with just a few snow patches appearing in the far eastern corner of Siberia and a splattering of snow in northern Canada. But Siberia is quickly cooling off as it progresses toward its winter pattern. So, I expect to see snowfall ramp up quite a bit over the next 4 weeks.

It's really too early to garner a lot of useful data here. But, over the next 4 weeks, snow cover will vastly increase across Eurasia and northern Canada. So, by the end of October, we should see a clearer signal as to how things could go.

Solar Activity:

We’re at a solar minimum.

In December of last year, we left solar cycle 24 and are now in solar cycle 25.

The GWV solar activity tracker shows that solar activity is still at very low levels, with no visible sunspots on the solar disc today.

There is a correlation between solar activity and the Polar Vortex. Commonly during a solar minimum and a west based QBO the odds greatly increase that we will see a strong Polar Vortex. With the QBO trending west and the fact we’re in a solar minimum it seems quite likely the PV will be stronger than average. This would also mean the odds favor a positive AO and NAO which would make it less likely to see a lot of blocking setting up.

Tropical Activity:

It is difficult to extrapolate a lot in this category. We’ve had a lot of named tropical activity, but the Accumulated Cyclone Energy Index has been more or less close to average. There is a weak correlation between an active Atlantic Hurricane Season and colder and snowier winters along the East Coast. My take on the discrepancy between the amount of named storms VS ACE, indicates there is an increased chance for warmer temperatures and less snowfall in the Northeast and Mid-Atlantic for winter 2020-2021. But we still have October and November to go through, so there is time for the ACE value to recover. So, there is the hope that we could salvage more of an average winter out of it.

Bottom Line:

Generally, this is looking to be a warmer than average winter. Overall temperatures across the entire Northeast and Mid-Atlantic should run 1°F to 5°F above average the warmest areas look to be the Middle Atlantic, Pennsylvania, much of New York State into Southern New England. Across Northern New York State and Northern New England look to end up slightly above average overall.

December into early January will have some cold shots. But by Mid-January and most of February it looks to be quite warm. Then we most likely will cool back off for March. So, based on how things look right now, the odds favor an overall warmer than average winter here in the Northeast and Mid-Atlantic

La Nina winters on average produce less than average amounts of snow. But given the facts I’ve gone over, Snowfall should end up 90% to 75% of average across the entire Northeast and Mid-Atlantic, the farther north you go the better your chance of seeing more in the way of snow. Winter 2020-2021 has a good chance of seeing more rain and mixing events this year, as compared to average.

Here are a couple of maps that show my overall Ideas for winter 2020-2021. Remember amounts can vary across different areas depending on storm track and local factors. This is a general overall look ahead.