It’s November 12th ,
as I’m writing this, our first major
arctic front of the season is rolling through, it is quite blustery and cold outside, and it's
getting colder. To get this kind of digging arctic front this early is quite
rare. Many of us in Pennsylvania, New York State and
New England have seen measurable snow. So, with Thanksgiving right around the corner,
many of y'all are wondering what to expect for this upcoming winter. If you don't want to read all the meteorological data and analysis, you can skip to the end of the post.
Over the last couple of years, I've found when dealing with my
seasonal outlooks. it's better to release a few installments leading up to my
official outlook. In that light, I've already released my preliminary outlook
and a subsequent update. You can find them at these links
OK let’s get started:
Meteorological Winter officially starts December 1st,
astronomical winter officially starts on Saturday December 21st. I
started trying to figure out clues for winter 2019-2020 back during the summer.
Even back in July, I was fielding questions on my winter thoughts; So, I know
many of y'all have high expectations. But I also know there are snow lovers who
are excited about the coming winter, and winter haters who dread what is
coming. So, it's nearly impossible to make everyone happy.
This outlook covers the December through February time period.
One thing I want to point out, this outlooks forecast is a little
warmer overall than some of the analogs indicate. My biggest worry concerning
this outlook, is that I’m being too conservative with my temperature ideas…
My Analogs:
1917-1918, 1961-1962, 1969-1970, 1981-1982, 1983-1984, 2004-2005 (double weighted), 2013-2014
(triple weighted), 2014-2015 (double weighted), 2018-2019
When looking at the SST anomalies; the closest matches are
2004-2005 2013-2014, and 2014-2015. 1977-1978 and 2002-2003 just missed as analogs; so they still have to be factored in somewhat.
Let’s take a look at current anomalies and teleconnections:
The first thing that sticks out is the warm SST anomalies in the
Northeast Pacific. But also showing up is the warmth off the East Coast of the
CONUS; the warmer tropical central Pacific and the cooler SST off the tropical
West Coast of South America. We can also see the warm SST in the western Indian
Ocean. All of these are shouting this
winter won’t be like last winter.
During the last month, SST in the equatorial Pacific have been
above average in the western-central Pacific. The eastern Pacific has seen
below average SST
The El Nino Southern Oscillation (ENSO):
For the spring and summer of 2019, the ENSO was in a weak La Nina.
The ENSO became neutral late summer.
But the Southern Oscillation Index has been negative and has
caused the ENSO to warm in ENSO region 3.4. ENSO region 1+2 is still colder
than 3.4.
So, the ENSO is trying to trend toward a weak Modoki El Nino.
The vast majority of winters that experienced ENSO neutral or a
weak El Nino, underwent above average snowfall and below average temperatures,
across most of the Northeast.
Weak El Nino’s typically bring much colder than average
temperatures to the Eastern CONUS for December, January, and February.
Warm Neutral ENSO conditions typically aren’t quite as cold as
Weak El Nino’s, with a slightly warmer December and cold for January and
February, with the cold more in the Northeast.
Everything is pointing to the idea of the ENSO staying neutral
warm with a Modoki look, into Spring
2020.
Everything is pointing to the idea of the ENSO staying neutral warm with a Modoki look, into Spring 2020.
The 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 warm water off of coastal Alaska. This is showing that Currently the PDO is positive. Overall the PDO has been positive since 2006.
When the PDO is strongly positive many have named this the
"The Warm Blob" Historically one of the biggest factors for cold and
snow in the Northeast is warm water in the northeast Pacific.
Persistent warmer than average SST in the northeast Pacific during
the winter season is typically associated with upper level ridging near Alaska
and along the Canadian West Coast into the Pacific Northwest of the CONUS.
The Indian Ocean Dipole (IOD):
Currently we have cold SST Southwest Pacific in the eastern Indian
Ocean, warm SST in the western Indian Ocean. So right now, the IOD is a fairly
strong positive. Over the last several years there have been positive IOD
during all phases of the ENSO. Several strong IODs during moderate to
strong El Nino’s averaged warm in the Eastern CONUS and cold in the Western
CONUS. On first blush this would seem to be saying a warm winter is in
store for the Eastern CONUS.
Given the idea that the ENSO is going to be very weak to neutral,
if we remove strong El Nino's and strong La Nina's, the temperature outlook for
the Eastern CONUS changes dynamically.
The positive Indian Ocean Dipole has only occurred three
times without an El Nino….1961-1962, 1982-1983, 2012-2013
The Quasi-Biennial Oscillation (QBO):
The QBO is currently west based, meaning it is positive. Some of
the snowiest winters here in the Northeast have featured a west based QBO. But
that isn’t always the case. A negative QBO often supports a setup for high
latitude blocking. A negative phase in the QBO also typically leads to a weaker
polar vortex. Making cold intrusion into the CONUS more frequent.
The QBO does seem to be trying to tend east (negative). Recently,
the QBO has been descending toward 30mb.
While this will have implications on the winter ahead, it is unclear how
quickly the QBO will descend
The AO and NAO:
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.
A negative NAO generally doesn’t bring the cold air but 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 slows down storms,
allowing them to become stronger. It also helps promote a stormier pattern here
in the Northeast.
In 2018 the AO and NAO were primarily positive. In fact, on average the NAO has been in a
positive phase since 2013. But in recent months the AO and NAO have largely
been neutral or negative. If this pattern continues, we should see more arctic
intrusions (like the one currently overhead) this winter. This would favor
above average snowfall and below average temperatures across the Great Lakes,
Northeast, into the northern Mid-Atlantic Region. Most of the models are
showing the NAO staying on the positive side on average for this winter.
However, many of the teleconnections like a declining QBO and low solar, are
hinting at the AO and NAO sticking overall to the negative side for this coming
winter.
The 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.
The MJO is most active during neutral phases of the ENSO. With the
ENSO looking to be warm neutral and the IOD looking to stay positive, I think
any move of the MJO into warmer phases would be very short. So, it won’t take
long for cold air to rebuild back into the region. Shorter stints of warmer temperatures would
naturally increase the snow chances.
The MJO has been moving toward a signal indicating high-latitude
blocking. This sometimes includes a negative NAO and AO, which correlates to a
cold and stormy pattern for the Mid-Atlantic and Northeast.
When the PNA is negative we typically see a trough in the west
CONUS and a ridge in the east CONUS. A
positive phase of the PNA typically promotes a ridge in the Western CONUS with
a Trough in the Eastern CONUS. The PNA is currently positive, that means we typically
see colder temperatures in the Eastern CONUS.
The Eastern Pacific Oscillation (EPO):
Solar:
When we look at recent solar minimum years, 500 mb height
anomalies. There is definitely a correlation between low solar activity and
higher than average geopotential heights over Greenland and Iceland. So, with this being the weakest solar year in
over 100 years; there is a good chance for a lot of upper latitude blocking,
leading to sustained cold air outbreaks over the central and eastern CONUS.
With the increased likelihood of cold, higher snow amounts than average is also
a good bet. I will go a little more
in-depth to explain why.
In the previous two prewinter outlooks, I talked about how we're
now experiencing the weakest solar minimum in the last 100 years. Because of
this I think we will end up seeing a few sudden stratospheric warming
(SSW) events this winter. SSW seem to be more likely during Solar
Maximum and Solar Minimum. The Quasi-Biennial Oscillation (QBO) phase is
tied into this SSW are more likely when the QBO is in its westerly phase during
Solar Max. On the other end of the spectrum, SSW are more likely when the QBO
is in its easterly phase during solar Minimum. Currently the QBO is
trending east. During the last solar minimum of 2008-2011 the Arctic
Oscillation primarily trended negative. So, I'm expecting this winter to see
the AO act similarly, and maybe the NAO as well.
Snowfall anomalies:
Over the last few weeks, there has been an observed rapid
advancement of snow cover over Eurasia and North American. 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.
All of these SST Anomalies and teleconnections are important. The
warm SSTs in the Central Pacific, colder SST in the eastern Pacific, and the
warm blob in the North Pacific, do point toward a colder pattern for areas east
of the Rockies.
So, if there isn't going to be an El Nino, with a warm IOD; the
overall SST setup in the Pacific is certainly a cold pattern for the Northeast
and Mid-Atlantic.
The general pattern should look basically like this for this winter
The 500mb Heights for and around North America look like
this.
The Warmth in the Gulf of Mexico and the Western Atlantic is a sign
of above average precipitation this winter.
Warm dry Octobers typically lead to warm winters. October 2013 one
of the analog years, was a very wet month. Many of the other global indices I
look at also match up well with October 2013.
When looking at past Novembers and winter temperatures; 60-70% of
years that saw a cold November ended up with a colder than average winter in
New England. November has been cold. Currently we’ve been seeing very better
cold air overhead across the region. Back in 1917, a severe arctic outbreak
occurred during November, similar to what we’ve been seeing this year. Typically, we see December warm after a cold
November. But not for the winter of 1917-1918; that winter started out brutal
and stayed brutal for the entire winter.
For this year’s winter outlook, I’m going to try and provide some
insight not only the general idea, but also into the individual months of
December, January, and February.
Temperature and Precipitation Outlook:
Overall Winter 2019-2020 will be colder than average, average, to
slightly above average precipitation, Snowfall will be above average across the
entire region.
The analogs are much colder than my outlook. So, there is a chance
the winter could end up overall much colder than I’m indicating. But I do favor the idea of some kind of bookend winter, it should start out cold, then some kind of warming before the cold comes back to end the winter.
I am concerned that this winter could feature a couple of notable ice storms.
I am concerned that this winter could feature a couple of notable ice storms.
December:
January:
The colder than average temperatures should return during January. But some of the warmth from December could linger into the first part of the month. January should see a return to tendency
supporting high latitude blocking. The pattern we look to see, would translate
to greater cold chances farther east, winter storms will be more numerous across
the Midwest, Great Lakes into the Northeast and Middle Atlantic.
February:
March into April:
Lake Effect Snow for winter 2019-2020:
SST temperature in Lake Erie are slightly above average at around
11-12 C
SST temperature in Lake Ontario are even warmer, at around 12-13
C.
Given the idea that the general overall pattern is going to
feature ridging out west, with troughing in the east. The pattern should
support the flow coming out of the northwest to west. With lake waters so warm
in Huron and especially Erie and Ontario, the cold air flowing over the lakes
should generate a lot of lake effect snow. This is why my snowfall totals for near the Great Lakes are so high.
In Summary, this will be a colder and snowier winter season in the
Northeast and northern Mid-Atlantic region. I think there is a greater chance
for blizzards this winter, especially across the interior Northeast.
Remember, a seasonal outlook is about the general pattern and most
likely outcome from that pattern. It is not meant to be an exact forecast. As was
the case last year (and any year really) there will be areas that over-perform and
under-perform from what I’m showing.
I want to take time to thank you for reading my thoughts on winter
2019-2020. If you have questions not
covered in this outlook….or general questions about the upcoming winter please
ask.