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.
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.
The location
of the warm spot should encourage more in the way of a positive Arctic Oscillation
(AO)
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.
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.
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.
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
My second
installment will be posted end of October. I will make adjustments based on the conditions at that time.
