This Winter forecast has already undergone some significant changes. When I initially began the Winter 2016-17 outlook during
the middle of October, I was significantly more "bullish" on the overall winter than I am now. The appearance and persistent
position of the Polar Vortex (PV) in Siberia and the enhanced Pacific jet stream over the past few weeks are somewhat troubling
signs. That being said I am not “bearish” or “fading” (to use trading terms) the winter of 2016-17 especially over the
central and eastern CONUS. But the appearance of these two important factors in November along with some strange behavior
by the QB0, do have me somewhat concerned with respect to WHEN the winter pattern is going to setup and how severe it
may or may not be.
What you will not see in this winter forecast are predictions for snow fall amounts. In dealing with seasonal forecast it is hard
enough to figure things out without having a guess about snowfall amounts for particular cities / regions. I know a lot of TVmets
do this sort of thing as do some private forecasters, but here at WxRisk.com ,we do not BS.
If you want to skip all the science (I dont know WHY anyone would want to do such a thing but there are some freaks out) use
the other link, or scroll down to the end of this report . However, it is our view that doing the science and going through the
steps is as important as coming up with the right answer. A lot of people don't understand this as the emphasis in our culture is
on getting the right answer. For example If I forecast the winter pattern based upon the number of socks in my dresser draw
and the forecast turns out to be correct it doesn't mean my technique was scientifically based and/ or it can be used in the future.
Winter of 2015-16 was an exceptionally mild winter over most of the
country because of the super powerful El Nino event. The month of
December 2016 may have been one of the warmest Decembers on
records especially east of Mississippi River. The super El Nino event has
faded but there is still some residual warmth left in the atmosphere. Even
though there was a massive snowstorm on the East Coast at the end of
January 2016, most of the country saw below normal snowfall as well.
The main issue for this winter will be a weak La Nina event but even that presents a lot of uncertainty as to whether not it is going
to continue through the Winter or fade to neutral conditions as we begin the heart of the Winter. Perhaps the biggest dilemma of
the winter -especially for the first half - is the appearance / position of the polar vortex (PV) centered not in western hemisphere
but over in Siberia on the Russian side of the Arctic circle. Having the PV in that location is a very bad sign for those hoping
for an early start of the winter over any portion of North America.
KEY FEATURES
The weak La Nina event - generally a neutral or favorable factor over the central and eastern U.S. with regard to running
either an average or above normal and temperatures running either average or below normal
The near record snowpack over Siberia in October 2016 which is spread rapidly westward into central and Western
Russia over the past two weeks. - a favorable factor over the central and eastern U.S. with regard to running either an
average or above normal and temperatures running either average or below normal
The strong indications for high latitude blocking patterns - a favorable factor over the central and eastern U.S. with regard
to running either an average or above normal and temperatures running either Below Normal or much below normal
The weakening and decreasing amount of solar activity - generally a neutral or favorable factor over the central and
eastern U.S. with regard to running either an average or above normal and temperatures running either average or below
normal
The development of a large pool of warm ocean water temperature anomalies in the northern Pacific. - favorable factor
over the central and eastern U.S. with regard to running either an average or above normal and temperatures running either
average or below normal
NEGATIVE FACTORS
The early season development of a the POLAR VORTEX (PV) overnorthern Siberia and locking into that position.
This can be considered to be a unfavorable, if not hostile factor, with regard to seeing either average or above normal snowfall.
Temperatures will likely run either average or Above normal for the central and eastern U.S as long as the PV stays in Siberia.
This is considered to be a positive factor however for the western third of the CONUS with respect to Above Normal precipitation
and Below normal temps. That being said it needs to be kept in mind that it is still mid November and the odds significantly
favor the PV shifting from its current position in northern Siberia.
The very strong enhanced Pacific jet which is dominating the northern hemisphere pattern - this can be considered to be a
unfavorable if not hostile factor with regard to seeing either average or above normal snowfall for the central and eastern U.S..
Temperatures will likely run either average or Above normal for the central and eastern U.S as long as Pacific jet continues to be
enhanced. In the weather biz, this is often call the “Pacific Jet firehose” . This is considered to be a positive factor however for
the western third of the CONUS with respect to Above Normal precipitation and Below normal temps. But again it is still early
and the odds significantly favor strong Pacific jet stream breaking down and allowing for a significant change in the pattern at
some point during the winter season .
DETAILED DISCUSSION
The weak La Nina event
These two images show comparison between the global sea surface temperature anomalies (SSTA) from DEC 2015 and early
November 2016. The most important feature of course is along the equatorial Pacific or the large area of above normal sea
surface temperature anomalies can be clearly seen. The contrast with the area of below Normal Sea surface temperatures in
the current November 2016 map is quite striking.
This image shows a comparison of the subsurface conditions along the equatorial Pacific across the various ENSO regions.
The cold water is fairly deep underneath the surface but it is not particularly intense and is rather indicative of a weak La Nina
event.
This next image shows the current plots of the various ENSO regions along the equatorial Pacific. Notice that over the past 30
days only the region known as ENSO 3.4 has been close to the minimum threshold for weak La Nina conditions.
So the question now becomes what happens to this weak La Nina event as we move into the winter months. ?
Most of Model data suggests that the current weak La Nina is going to break down and dissipate early in the winter and that
most of the winter will see near neutral conditions. Other data suggests that the weak La Nina will hold on for most of the winter
only dissipating in February 2017. So let's consider the two possibilities.
LA NINA DISSIPATES IN DECEMBER 2016
If we take a look at all the seasons where there has ben a weak La Nina in the Autumn which dissipated during the Winter months
we come up the following analog years. 1962-63 1983-84 1996-1997 2005-06 2008-09 2013-14
The first map shows the overall pattern for those winter analogs and we can see a persistent deep trough covering most of the
central and eastern CONSU that favors a cold and potentially stormy winter pattern. In addition most of western and central
Europe also appears to be quite cold and stormy. This sort of pattern supports strong blocking across the arctic regions, especially
over Greenland and Scandinavia as well as the Bering Sea. If we break this down month by month, we see that the Jet stream
patterns remain quite impressive with a massive deep longwave trough over the central and eastern portions of the CONUS
as well as western/ central Europe. The analog of Winters that featured weak La Nina in Autumn that dissipated in the
Winter suggests that the Month of February could be particularly cold and stormy for the eastern half of the CONUS.
This map shows temperatures and precipitation for the selected analog years. Notice that the lower Plains look to be fairly dry.
However temperatures are quite cold relative to normal over all the Midwest and the interior portions of the East Coast .
Taking a look at the temperatures and precipitation for December, January and February it appears that December is particularly
cold and wet especially along the East Coast and quite cold over the upper Midwest and much of Canada. According to this
analog, January features large areas of below normal temperatures across all the Midwest and most of the East Coast with near
normal or slightly below normal precipitation. Over the lower Plains and the Delta region, it appears to be somewhat drier than
normal. February appears to show the large area of cold temperatures diminishing and much of the lower Midwest and portions of
the East Coast turning somewhat drier than normal.
WEAK LA NINA LASTS THROUGH THE
WINTER
Now let's take a look at what happens if the weak La Nina event stays on through the heart of the winter. The analog years are
the winter of 1950-51 1954-55 1964-65 1967-68 1971-72 1984-85 1995-96 2011-12. This image shows the overall large
scale pattern over the northern hemisphere for those analog years. As you can see the pattern features a deep and persistent
trough over Western Canada into the Rockies and the upper Plains. The RIDGE position is not on the West Coast, but over
eastern Pacific Ocean which is not favorable for winter weather lovers over the eastern U.S. In addition, notice that there is some
sort of Ridge over far southern Greenland and central north Atlantic. This is often mistaken as a Greenland block or a negative
phase of the NAO. However to call this feature a Greenland block or -NAO would be a serious mistake. This kind of positive
Height anomaly supports a “North Atlantic THUMB Ridge” which is not the classic / Greenland block -NAO. In the overall
sense this sort of pattern would support a favorable winter pattern for the Rockies Upper Plains and Midwest but not the East
Coast. It is not a terrible pattern for winter weather lovers over the eastern US --just not ideal.
As you can see temperatures run below Normal over the northern 25% of the country with temperature actually above normal over
the Deep South. Precipitation is near normal everywhere.
These graphs show the overall seasonal snowfall amounts for the 3 major cities in the Northeast US I-95 corridor or
the La Nina Neutral and El Nino events (Strong/ Moderate/ Weak). These graphs show some interesting trends. For
New York City there is a wide spread of snow fall amounts for the season ranging from almost nothing to extreme snowfall
amounts.
For Washington, DC and Northern Virginia, with the lone exception of the winter of 19951996 most weak La Nina winters feature
below normal snowfall.
The data shows that with weak La Nina winters Boston also have a large spread of seasonal snow fall amounts. This also
appears to be the case of near neutral conditions and weak El Nino conditions.
And when we take a look at Chicago, we again see a fairly extensive spread when it comes to weak La Nina events and seasonal
snowfall.
That being said the weak La Nina analog years 1950-51 1954-55 1964-65 1967-68, 1971-72, 1984-85, 1995-96,2011-12
is a pretty mixed collection of very different types the winters. If we take a look at these weak La Nina Winters with a little more
focus, we notice that many of these years were actually winters which featured prolonged La Nina events that had been going on
for over year and some of these analogs La Nina events were are actually much stronger at one point in the cycle. So not all of
these weak La Nina analog years are good matches to the current situation.
If we keep in mind that we have come out of a fairly strong El Nino event from last winter ,which finally ended in the Spring of
2016, with near neutral conditions for the Summer of 2016, .which have now developed into weak La Nina conditions in the
Autumn, we find three close analog maches.: The winters of 1954-55, 1964-65, and 1995-96.
This image shows the overall large scale hemispheric pattern for those three analog winters. It is similar to the previous analog
which featured all the winters that had weak La Nina events but with one major change. The north Atlantic thumb ridge appears
to be much stronger and much larger and could now be considered a legitimate Greenland block /-NAO feature.
The temperature patterns show much colder conditions across the Great Lakes and the Northeast U.S. While the lower Plains
and the Southwestern states stay fairly mild. Precipitation appears to be above normal over the Middle Atlantic region and the
Pacific Northwest.
The near record snowpack over Siberia in October 2016
The data from October 2016 shows that the Siberian snow cover was extensive and near record. In fact it came in as the third
greatest snow cover for the month of October over Siberia on record. The reason why this is important is because the expansion
of the snow cover especially south of 60° N latitude in the month of October, seems to have some sort of correlation to
development of blocking patterns in the Jet stream over the Arctic region. This in turn ends up impacting the weather patterns
over all of North America especially in the second half of the Winter into early Spring. The technical name for this phenomenon is
called the Siberian Advance Index or SAI.
There are of course exceptions to this. Last winter for example we have
the raging super El Nino so even though the snow cover was fairly
extensive for the month of October 2015 over Siberia, the SAI had little
impact.
In addition the extensive or geographical size of the snow cover in Siberia
was also extreme during the month of October 2016. This aspect of the
snow cover in Siberia is known as the Snow Cover Extent or SCE. It
does not get as much attention as the SAI but the SCE in out view is
quite important. One can have what would seems to have a favorable
overall hemispheric pattern which appears deliver cold air and winter
storms for the central and eastern portions of the CONUS. But if the
supply of cold air coming from Siberia is weak, the cross polar flow from
Siberia across the Arctic region into Canada can become problem for
setting up the classic winter storms (which require a large supply of Polar or Arctic air).
So in summary both the SAI and SCE numbers and correlations are very strong positive with respect to the potential for this
winter over the central and eastern U.S..
The strong indications for high latitude blocking patterns AO/ Arctic Oscillation
The Arctic Oscillation is a climate index or major weather pattern (atmospheric circulation ) that plays a huge role in weather
pattern over the entire northern Hemisphere. The AO's impact is especially significant from October to April. The
AO has so-called “positive” and “negative” phases. When the Arctic Oscillation is in the negative phase, cold Arctic air masses
tend to plunge southward and into the U.S., spawning snowstorms and leading to colder than average conditions. This is because
a Negative AO will a weaker PV (Polar Vortex)… OR several mid size PV… OR…a PV that is strong but displaced well to
the south.
A “positive phase” for Arctic Oscillation, by contrast, tends to mean warmer than average weather with less snow for the eastern
U.S. This is because a Positive AO means large strong PV over the Arctic regions / and or Greenland which locks up he cold to
the north and prevents the northern jet stream from merging with the southern jet stream (it is this phasing or merging of the 2
Jet streams that create big winters storms).
Research has long established that the phase of the Arctic Oscillation during
the month of October is often a indicator of what phase the AO is more likely
to average during the course of the winter months of DJF. There is some
uncertainty as to why this is the case but the data is pretty strong that there
seems to be some sort a correlation. Assuming this is correct, if we take a
look of the Arctic Oscillation over the past 5 months, we see a very strong
and noticeable dip in the AO into the Negative phase during the month of
October.
The Arctic Oscillation can vary considerably on short timescales, such as
within a single month or from one month to the next, and the causes of its
variability aren’t entirely known. It was largely positive during the winter of
2007-8, which followed the previous sea ice record low, and then turned record negative during the winter of 2009-10, during
which the infamous “Snowmageddon” blizzard occurred along the East Coast. It was then largely negative during the winter of
2010-11, and positive to weakly negative last winter, which was the mildest winter on record for the U.S.
Over the past two or three weeks there been numerous reports of extremely low Arctic sea ice relative to normal. The
temperatures in the Arctic region are extremely warm for late October and early November. There are several reasons for this
but perhaps the primary reason is that the PV -Polar Vortex -is currently located in Siberia and not over the Arctic region where
typically is located in early November. The result of this very warm Arctic region for early November in showing up with much
below normal arctic sea ice.
In addition the noticeable lack of the sea ice and extremely warm temperatures relative to normal over the Arctic region seems to
also favor the AO running negative as the earth tries to maintain some sort of balance. There have been several significant
research papers over the past 5 to 10 years that have established this connection
One way that Arctic sea ice decline could result in the increase in the Variability of extreme winter weather is by changing either
the effects of the Arctic Oscillation or the workings of the oscillation itself. So while it may be counterintuitive the lack of sea ice in
the arctic region in late October and the first half of November may actually help bring about a prolonged negative Arctic
Oscillation phase later on in the winter season.
The weakening and decreasing amount of solar activity
Research and actual observations have shown that weak or low solar activity tends to be correlated with frequent blocking pattern
in the Jet stream at the high-latitudes. Currently the Sun is now experiencing one of the weakest solar cycles (#24) in more
than a century. Moreover as you can see from this image the already weak solar cycle is headed rapidly towards the next
solar Min - usually the least active time in a given cycle.
If we take a closer look at this sun cycle chart will see
something quite significant. Notice that the solar / Sun
minimum occurred in 1984-1985 1995-6 2009-10 or
all winters which featured extreme cold and some serious
snow storms across portions of the Midwest and the East
Coast. In particular the winters of 1995-96 and the winter
of 2009-10 featured major East Coast and Midwest snow
storms that set records for seasonal snowfall and many
areas. This also has some significance for the future
winters as it looks like the Sun will be reaching a strong
negative solar minimum in the winter of 2019- 20.
The development of a large pool of warm ocean water temperature anomalies in the northern Pacific.
Besides the weak La Nina there is another important feature in the Northern Pacific Ocean that deserves considerable attention.
The severe historic winter of 2013-14 was totally and completely under forecasted by CPC (Climate Prediction Center) and by
most if not all private forecasters. The driving factor in that surprisingly severe and cold winter was a development of a large pool
of warm sea surface temperature anomalies (SSTAs) in the Gulf of Alaska and the northeast Pacific Ocean.
This feature helped to bring about a somewhat rare and not
well known weather pattern in the jet stream known as the
+TNH or positive phase of the Tropical Northern Hemisphere
pattern. This pattern is frequently confused with the much
better known jet stream pattern known as +PNA.
This image shows the development of a large pool of
extremely warm SSTAs in the northeastern Pacific that appear
in October 2013. This feature persisted right through the
winter... and into most of 2014. Indeed this feature what
actually contributed to the colder than normal and fairly stormy
winter of 2014-15.
This next image shows the difference between the +TNH and + PNA patterns. In the +TNH pattern, the mean ridge is located over
the eastern Pacific/ West coast with a highly amplified Ridge that extends into Arctic region (-EPO). This establishes a cross
polar flow and brings numerous Arctic air mass outbreaks to much of the Plains, the Midwest, the Deep South and the East Coast.
However because of the position and shape of the long wave trough the Arctic Oscillation, stays neutral or positive. As a result
the +TNH pattern often brings numerous moderate size snow storms but often lacks large scale intense LOW pressure
areas .
The Classic +PNA pattern features the trough ON the West Coast or sometimes as far east as the Rockies. This in turn
changes the entire shape of the pattern and when the Arctic Oscillation and North American Oscillation (-NAO) turns negative
that pattern supports large scale winter storms over the Midwest and East Coast.
All that being said let's focus on what is going on in the northern Pacific in October and November 2016. This map from
beginning of October 2016 showed that another large pool of exceptionally warm SSTAs had developed over the Northeast
Pacific Ocean in and around the Gulf of Alaska. This is very similar to we saw in the Autumn of 2013. This has led to some
speculation from some forecasters that the pattern may be a repeat of the severe winter of 2013-14.
That assumption has some validity to it but that assumes that the large pool of warm SSTAs in the northeast Pacific does not fade
and that it last into the winter months.
The problem is that because of the overall pattern across the
Pacific Ocean over the last 30 days, the large pool of warm sea
surface temperatures in the northeast Pacific weakened
considerably. The strong Pacific jet stream and a series of major
systems moving across the northern Pacific Ocean has caused
"upwelling" which is turns has severely weakened this large pool
of warm sea surface temperatures. These two images show that
changes over the last 30days - from mid October to mid November. Over the last 30 days we can see that the warm waters
over the northeast Pacific have almost completely diminished .
If the overall pattern begins to change across the northern Pacific over the next two or three weeks, it is still possible that the
pool of warm SSTAs will hang on and even Re-intensify as we move into the heart of the winter. If this were to happen it would
greatly enhance the probability of a colder than normal and snowier than normal winter for portions of the central and eastern
U.S.. Obviously this variable is going to be very important to watch over the next few weeks.
The early season development of a the POLAR VORTEX (PV)
position -
over northern Siberia and locking into
that
The very strong enhanced Pacific jet which is dominating the northern hemisphere pattern
Back in October and early November ...there was a lot of focus by various meteorologists on the development of unusual type of
weather Phenomena known as a Sudden Stratospheric Warming Event. (SSWE) The typical SSWE occurs late in December
or January and often leads to major pattern flip or reversal. But for some reason a SSWE occurred in late October/ early
November. This led to a lot speculation as to what it might mean for the winter over the northern hemisphere.
There seems to be a bias with a lot of meteorologists that assume ANY sort of SSWE implies that the pattern must lead to a
substantially colder and stormier pattern for the central and eastern portions of CONUS. While it could be argued that there is a
tendency for SSWE to favor a change in weather patterns which supports colder and stormier patterns for the central and eastern
US ...it is not all a certainty. There have been numerous examples SSWE which have resulted in colder and stormier weather
patterns developing over Europe / western Russia... eastern Asia.. or western Canada / Alaska regions.
In this particular case we believe that SSW event that took place in October and early November has locked the PV Polar
Vortex into position over Siberia. Although many forecasters believed that this early SSWE would lead to a much colder than
normal second half of November and early start of the winter over the central and eastern CONUS, WxRsik.com strongly
disagrees with that assessment.
It is of course impossible at this time to prove that the early season SSW -sudden stratospheric warming - which developed
over the arctic region in late October and early November has led to the unusual and very powerful PV being situated over
Siberia. But we stand by that hypothesis.
It is hard to overstate how critically important the
position of the PV being located over Siberia is with
respect to the overall winter pattern to the northern
hemisphere pattern in general and the western
hemisphere pattern specifically.
For those looking for an early start to the winter having
the PV situated in eastern Siberia is thee kiss of death.
Here is why
1. First it pulls all the arctic air out of the
northern regions of Canada and the arctic
region itself. The numerous stories which have
appeared in the media recently about the
exceptional warmth relative to normal over the
arctic region is in part attributable to the unusual
position of the Polar Vortex that is currently
located in Siberia.
2. Having the PV in eastern Siberia ensures that the Pacific jet that leaves China and Japan will streak across the Northern
Pacific Ocean with enhanced with velocities and intensity. This image shows the impact of the deep PV over in
Siberia is having on the Pacific jet stream. This image shows that the civic jet stream has been running at 200 knots or
250+ mph. It is Extremely difficult to get the overall pattern to shift / change when the jet stream is that zonal and
that fast. Indeed the enhanced and powerful Pacific jet slamming into the West coast of North America is the primary
reason why the area from British Columbia to central California have seen a barrage of powerful weather systems that
have brought much above and extreme much above precipitation to that area over the past 45 days.
3. The enhanced zonal Pacific jet stream overwhelms
Southern Canada with mild air as well as most of the
U.S.. Temperatures consistently run above normal and
the snow cover over the southern half of Canada can be
greatly diminished. In fact last week most of the snow
cover over southern Canada had completely
disappeared because of the extreme warm (relative to
normal). And without the early season snow cover in
southern Canada ,even cold air outbreaks when they do
occur, have a lot less staying power over the CONUS.
4. The zonal and enhance Pacific jet stream means that it
is impossible to get any sort of RIDGE to form over the
West coast of Canada. And without that RIDGE ...there
is no mechanism to deliver cold air into the central and
eastern portions of the CONUS
All that being said, we believe that the Polar Vortex will eventually move from its current location in eastern Siberia back
into the arctic region. In doing so it will lead to a chain of events that will bring in a more typical winter like pattern for the
western hemisphere. However, this could be a fairly long process. First, if and when the PV leaves eastern Siberia and moves
back into the Arctic region... the depleted sea ice will have to regenerate. Next, the cold air over Northern Canada will have to
move southward establishing snow cover over South central Canada. 3rd, the pattern will have to shift so that the Pacific jet breaks
down but and a RIDGE becomes established over western Canada. Only when all three of these items have developed , will the
pattern turn back to a seasonal early winter pattern.
The Quasi-Biennial Oscillation or QBO is one of the most remarkable phenomena in the Earth's atmosphere. High
above the equator, in the stratosphere, strong zonal winds blow in a continuous circuit around the Earth. These winds might start
as westerlies, but over time they weaken and eventually reverse, becoming strong easterlies. The whole cycle progresses at a
fairly (but not entirely) uniform rate, taking on average 26 months to return to the starting state.
Why is the QBO important? It is certainly relevant for seasonal prediction, where the state of stratospheric winds affects
interactions between the tropics and the mid-latitudes, and may also affect the tropical troposphere directly and possibly how the
solar cycle interacts with the atmosphere.
Without getting too technical it is believed that the energy from the winds in the QBO propagate or move downward into the
jet streams and help enhance or in some cases weekend the jet streams. Moderately strong Eastward phases of the QBO
often coincide with more sudden stratospheric warmings (SSW) , a Polar jet stream, more blocking patterns and cold winters
in Northern Europe and eastern USA. Conversely, Westward phases of the QBO often coincide with mild winters in eastern USA ,
less blocking patterns, stronger than usual Pacific jet stream.. wet and chilly winters over most of western North America, and
mild, wet stormy winters for Europe.
Currently the QBO is running quite strong out of the west. This LINK shows a sample of the QBO data that meteorologists have to
look at and as you can see this particular data goes back to 1954. However for our purpose, we want to focus on the last two
years. This image shows what has happened with the QBO over the last two years. As we stated above typically the QBO
goes through these cycles where it starts off ,for example, positive (West to East) then weakens to Neutral then drops down to into
negative (East to West) then moves back to Neutral and then back into Positive and so on and so forth.
This appeared to be what was happening as we move from the winter of 2015-16 into the Spring of 2016 Coming out of this
winter the QBO was still positive but it was dropping rapidly towards the neutral values and by April the QBO was near neutral.
At that point it should have been continuing to drop into the negative values but for some reason which is not clear the QBO
reversed and started becoming positive or Westerly once more. The October 2016 value is +12.83 which is quite strongly
positive. While it is true that QBO values will oscillate back and forth from time to time and month to month, what we are seeing
here is something quite different. Looking back at all the data since 1945 we have not seen a single QBO cycle which featured
the QBO values going from Positive to Neutral and then back towards Positive.
In addition there is quite a bit of evidence that suggests a strong
westerly phase of the QBO also favors a enhanced and active
Pacific jet stream.
Unless something dramatic happens over the next 60 days it is
pretty clear that the QBO is going to say strongly positive for
most of the winter. This can only be viewed as a hostile or
unfavorable factor for those winter weather lovers over the
central and eastern CONUS . For those areas on the West
Coast / Rockies having a strong westerly QBO favors these
areas with excessive or at least above normal precipitation and
even normal or below normal temperatures.