Winter '22 / '23 - Snowmageddon Weather in North America More Influenced by Tropics Than Arctic

"Winter weather patterns in North America are dictated by changes to the polar vortex winds high in the atmosphere, but the most significant cold snaps are more likely influenced by the tropics ..."

"The study, published in Geophysical Research Letters on December 27, 2019, also revealed that, unlike in Europe, the most extreme cold snaps affecting the whole of North America are not most likely to occur after a weak (polar) vortex. Instead, the shape of the vortex and conditions in the tropics were identified as stronger influences of these conditions"

More ...

Winter '21 / '22 - Quasi-Biennial Oscillation (QBO): OCT-21

-19.14 (just inside 1-sigma from the mean)

OCT is now the 5th month with a QBO index below zero having flipped in JUN following its 14 month run in positive territory.  The 30mb flow over the Equator oscillates from east to west every 14 months; therefore ... the current easterly state of the QBO is expected to last throughout Winter '21 / '22.

Leading analog years
Winter / ENSO (MEI)
72-73 / W+
00-01 / C-
09-10 / W
91-92 / W+
58-59 / W-

With La Nina temperature anomalies in ENSO Region 3.4 expected to persist through at least late winter ... all QBO analog years are rejected except Winter 00/01.

- Winter '00 / '01
The sum-total of the season-total snowfall for all Contest forecast stations was 1,312".  (~21% above the 1968 - 2021 period-of-record average 1,085".

Eurasia/s OCT areal snow cover slightly below normal.

D-J-F Index Averages
AO:  -1.312
NAO:  +0.040

"The QBO determines the character of the early winter, leading to a colder and more stable polar vortex in December and January during the west phase of the QBO and a more disturbed and warmer Arctic during the east phase of the QBO." [1]

In years with low solar activity (solar cycle 25 is just beginning) ... the polar winter vortex tends to be disturbed and weak when the QBO is easterly.  Positive geopotential height anomalies over high latitudes ... i.e., blocking ... are also correlated with QBO-E and solar minimums.

 

Antecedent odds currently favor a weak and disturbed stratospheric polar vortex and SSW (sudden stratospheric warming) leading to a long-lasting negative Arctic Oscillation (AO) and well-below normal temperatures periodically in eastern North America ... northern Europe ... or eastern Asia.

Winter '20 / '21 - How Arctic Amplification Affects the Polar Vortex

 "AER explains how accelerated Arctic warming, known as Arctic amplification, is increasingly disrupting the polar vortex, leading to widespread severe winter weather across the Northern Hemisphere’s mid-latitudes."

 https://youtu.be/EMeI4N5dui4

Winter '19 / '20 - What Is the Polar Vortex and How Does It Influence Weather?

"The term polar vortex has become part of the everyday vocabulary after the widespread media coverage of the extreme cold events over the United States during the early winter of 2014.

"However, there is some confusion in the media, general public, and even within the science community regarding what polar vortices are and how they are related to various weather events."
[...]
"... since surface weather disturbances are associated only with displacements of the vortex edge in limited areas rather than hemispheric-scale changes to the vortex, it is not clear ... invoking the term vortex clarifies anything, given ... the vortex is a hemispheric-scale structure.

"Use of the term without adequate explanation can suggest a more dramatic change to the global tropospheric circulation than has actually occurred (e.g., “The polar vortex is back!”)."

---
Learn more about the PV from the full article courtesy the Bulletin of the American Meteorological Society (BAMS) here.

Winter '18 / '19 - Sudden Stratospheric Warming: Watch #1 - UPDATE 3

 From Judah Cohen's (AER) blog ...

"I have been arguing for at least a decade now that the winter season is shifting ahead in time so that it starts later and ends later.  The fall months are warming across the NH (with one notable exception in Siberia) and that warming extends into December.  However surprisingly the next three months, January through March are cooling across the NH mid-latitudes.
[...]
"The frequency of severe winter weather is increased following an SSW across the NH mid-latitudes including more Arctic outbreaks and heavy snowfalls.  Therefore, temperatures are cooling for late winter starting in January and extending into March.
[...]
" ... if you are anticipating severe winter weather or a winter weather enthusiast the mild bland weather is necessary for a period of elevated risk of severe winter weather.  Sure, there has been nothing memorable (at least for me; not true if you live in the Carolinas or Virginia) about December but the non-first half of winter is not independent of what I anticipate is a more active second half of winter.
[...]
"So, if you are a winter weather enthusiast, at least in my opinion the lack of winter so far is a necessary condition for cold and snow to follow.  And if you like your winters mild then if the winter turns harsher in the near future it also was the cost for the benign winter so far.
[...]
" If the stratosphere and troposphere fail to couple, then I see no reason why the relatively benign winter weather can’t continue right up to spring.
[...]
"After the PV split the lowest heights and coldest temperatures are predicted to be in three regions in the stratosphere in Western Asia/Eastern Europe, the North Pacific and Southeastern Canada/Northeastern US.  The models all agree that in the troposphere the lowest geopotential height anomalies will also be in Western Asia/Eastern Europe and the North Pacific with the models only disagreeing in Southeastern Canada/Northeastern US.

"But for the biggest impact the Arctic in the troposphere needs to warm up in my opinion and that has not happened.  Also, the only region that is experiencing significant below normal sea ice extent is the Barents-Kara Seas.  If the positive temperature anomalies remain confined to this region this is supportive of cold in Asia but not eastern North America.[...] In fact, low sea ice in the Barents-Kara Seas favor warm temperatures in the Eastern US based on this plot alone."

Winter '18 / '19 - Sudden Stratospheric Warming: Watch #1 - UPDATE 2

Brief ... less dramatic stratospheric warming at 30 mb on 20-DEC-18 has faded only to be replaced by a much larger  ... stronger ... and very well modeled event with its sprawling center over the northern Asia continent.

Figure 1.  10 hPa temperature change in a week in the Northern Hemisphere
Contour interval:  5 °C.
PINK and light BLUE shadings indicate warming and cooling, respectively.
RED shading denotes warming for values higher than 25 °C.

Image courtesy:  Tokyo Climate Center, Climate Prediction Division

Figure 2.  10 mb Zonal Mean Temperature for 2017 & 2018
Note the sharp on-going increase in temperature (far right) and the previous SSW events during FEB-18 (center) and FEB-17 and again in MAR-17 (far left).

Image courtesy:  CPC Stratosphere's Global Temperature Time Series 

Figure 3.  Latitude-height cross section of zonal mean temperature
Note the descending bulge of warm temperatures in bottom row as the current SSW event unfolds

Image courtesy:  Tokyo Climate Center, Climate Prediction Division
 

Figure 4.  Latitude-height cross section of zonal mean wind
Note the descending blue region in last panel as the easterly wind (negative values flow into the board) begins to disrupt the polar vortex.

Image courtesy:  Tokyo Climate Center, Climate Prediction Division
 

Figure 5.  240-hr 10 mb zonal wind forecast
Note the PV split (sister vortices) over NE Europe and NE North America

Once the circulations work their way to the surface ... they're expected to bleed a mother lode of numbing Arctic air into the Upper Midwest and ooze its way deep into the southern tier of states.  Arctic boundary likely to drape along the eastern seaboard providing favorable baroclinic conditions for coastal cyclogenesis.

Image courtesy:  Freie Universität Berlin Institute for Meteorology - Stratospheric Diagnostics

Winter '18 / '19 - Sudden Stratospheric Warming: Watch #1 - UPDATE

Game On!
Major sudden stratospheric warming (SSW) in the cards and being dealt.

Figure 1:  10 hPa temperature change in a week in the Northern Hemisphere

Contour interval:  5 °C.
PINK and light BLUE shadings indicate warming and cooling, respectively.
RED shading denotes warming for values higher than 25 °C.
Image courtesy:  Tokyo Climate Center, Climate Prediction Division
 
Action center over Hudson Bay and much of Canada.

"A major midwinter SSW event occurs when polar stratospheric temperatures increase by at least 25 K in one week, and the zonal-mean zonal wind at or near 10 hPa (~30km altitude) reverses direction and becomes easterly north of 60° N."
REF:  NASA Global Modeling and Assimilation Office

---
NWP models continue projections for major SSW through month/s end.


Figure 2:  D+10 Latitude x height cross-section from EC prog

MAIN FEATURES:
- Stratospheric anticyclone progged to descend near the 20 mb level
Upper right corner - wind into the board ==> anticyclonic circulation

- Deep surface anticyclone at or above 500 mb
Lower right corner - wind into the board ==> anticyclonic circulation (Arctic surface HIGH)

Image courtesy  Wetterdaten des Meteorologischen Instituts, Standort Berlin-Dahlem

IMPACT:
"Pronounced weakening of the NH wintertime stratospheric polar vortex tend to be followed by episodes of anomalously low surface air temperatures and increased frequency of occurrence of extreme cold events throughout densely populated regions such as eastern North America, northern Europe, and eastern Asia that persist for ~2 months."
REF:  Thompson et al. (2002)

---
Also note QBO-W depiction at 30 mb over the equator.
QBO flipped from East (negative) to West (positive) in NOV.
Not necessary a good thing.

QBO-W associated with ...

• pressure differences over the North Atlantic tend to be greater, which strengthens the jet stream which increases chances of mild and stormy winter weather.
• geopotential height at high latitudes is significantly lower
• In years with low solar activity the polar winter vortex tends to be ... deeper and undisturbed ==> +AO ==> inhibits spillage of Arctic air into mid-latitudes.
• -PNA
• warmer SE states
• +NAO

Some of the very same things found to be associated with DEC not having a contest-worthy snow storm.

Winter '18 / '19 - Sudden Stratospheric Warming: Watch #1

Polar vortex (PV) displacement event appears to be in the cards come Christmas.

Full flow reversal + warming ==> major sudden stratosphere warming (SSW) event ...

BLUE:  into the board ==> east wind (-U)
ORANGE:  out of the board ==> west wind (U)

"A major SSW occurs when the 10 mb 60°N zonal mean zonal wind reverses from westerly to easterly and the 10 mb zonal mean temperature gradient increases poleward of 60°N." (.pdf)

---
Last winter's SSW event crash-landed over the UK (weeks of late season snow + cold)

This year ... round and round she goes.
Where she stops ...
Nobody knows.

Winter '17 / '18 - Sudden Stratospheric Warming: Watch #1 - Update 1

Full reversal at D+5 (12-FEB) comports very well with the earlier D+10 forecast.

 

Full reversal continues at least through D+10.

Huge implications for the weather associated typically with a negative Arctic Oscillation toward month's end and into MAR.

 

 

Where the AO/s full impact is wrt arctic/s cold air drainage appears to be on the other side of the globe under the 'W' ; however ... note the NW flow regime and +PNA is progged over CONUS.

Winter '17 / '18 - Sudden Stratospheric Warming: Watch #1

Something worth keeping an eye on ...

 

D+10/s polar vortex splits in two with action centers over northern Canada along ~90W and ~45E INVOF the Black Sea.

 

Deep layer ... high latitude flow reversal (negative / blue values into the board i.e., east wind / anticyclonic circulation) would provide highly favorable conditions for a negative Arctic Oscillation index over an extended period toward meteorological winter's end.

Winter '17 / '18 - Ignorosphere Tonight

Polar vortex centered over Barents Sea.
Anticyclonic circulation over NOAM

10 mb circulation

The HIGH made a strong attempt to displace the PV but will lose out shortly.

---
Image courtesy Earth

Winter '16 / '17 - Sudden Stratospheric Warming: Watch #2 - UPDATE 1

Displacement event/s peak progged for early next week.

 

PV displaced SW by warm pulse.

Center of anticyclone does not advance as far south as 31-JAN/s event.

 

 

 ---

 

Strong anticyclonic couplet above 10 mb

Winter '16 / '17 - Sudden Stratospheric Warming: Watch #2

Could be the season/s final stratospheric warming event.
Images from 15-FEB-17 ECMWF run.


Weak high-altitude zonal flow returns after the recent SSW event.

---

Flow above 30 mb reverses and strengthens as the PV is once again displaced.
Flow throughout the depth of the troposphere (evidence of the downward propagation from the previous SSW?) also reverses.

---

Cold pool from previous SSW event progged to settle above the NOAM/s Arctic Circle near month/s end.

Stratosphere Diagnostics courtesy Freie Universität Berlin

Winter '16 / '17 - Sudden Stratospheric Warming: Watch #1 - UPDATE 2

The well forecast major warming 'displacement' event is well underway.
Major warming:  temperature increase >= 25°C over seven days.

 

Stratosphere Diagnostics courtesy Freie Universität Berlin / Department of Earth Sciences / Institute of Meteorology  

 

 

 

 

Stratosphere analysis courtesy Tokyo Climate Center, Climate Prediction Division Japan Meteorological Agency

 

Winter '16 / '17 - Sudden Stratospheric Warming: Watch #1 - UPDATE

Displacement event looms near month's end.

 

 

---

QBO > 10 kt

Strong STJ (50 kt)

Weak PV (30 kt)

Flow reversals above 5 mb and below 300 mb

 

 

---

Cold air mother lode sits over Hudson Bay with full-latitude trough attending.

 

 

 

Winter '16 / '17 - Sudden Stratospheric Warming: Watch #1

A sudden stratospheric warming (SSW) event may be in the works for the last week of the month.

After weeks and weeks of a high-speed rotation ... polar vortex (PV) forecasts suggest a significant slowing / weakening.  Slowing of PV suggests a deep layer of easterlies (light blue; lower right corner) over the Pole.

A maturing of this scenario would portend Arctic air drainage into the mid-latitudes.


Stratosphere Diagnostics courtesy Freie Universität Berlin / Department of Earth Sciences / Institute of Meteorology

Winter '15 / '16 - Major Sudden Stratospheric Warming

Temperature change of -25°C over seven days & 10 mb flow reversal.



Images courtesy Japan Meteorological Agency.

---

Previous post:

Winter '15 / '16 - Sudden Stratospheric Warming:  Watch #2 

Winter '15 / '16 - Sudden Stratospheric Warming: Watch #2

UPDATE (01-FEB-18):
As advertised ...

 

 

Looks yuge.

Beat the rush.
Start laying in supplies now.

---

10 mb Temperature Anomalies
GFS Ensembles 10-JAN-16

"The models are now coming into better consensus for a stronger pulse of energy transfer beginning next week that is predicted to initiate a sudden stratospheric warming (SSW) at the end of the month."

 -  AER Arctic Oscillation Analysis and Forecasts (time sensitive)

Progs expect PV displacement v. PV split.

Winter '15 / '16 - Sudden Stratospheric Warming: Watch #1 UPDATE 1

ECMWF continues to signal PV weakening near month's end.

Initial panel (right) @ 80 m/s (155 knot; 179 mph).

D+10  @ 60 m/s (117 knot;134 mph).Also note the weakening +QBO feature INVOF 30 mb.

00 mb D+10 prog (bottom) signals the start of a splitting PV with circulation centers over the Laptev Sea (west of Barents Sea) and extreme northern Canada ... as well as the leading edge of a sharp wave over the Prime Meridian.

Takes a few weeks for a propagating wave to reach 10 mb then work its way to the surface.

Winter '15 / '16 - Sudden Stratospheric Warming: Watch #1

Following a recent cross-hemisphere shift of the polar vortex's (PV) center of circulation from NW Greenland to the Barents Sea ... the first signs of upward propagating wave energy have appeared on the ECMWF/s 13-DEC-15 100 / 70 / 50 mb progs.

The potential for a PV split faces a stiff headwind.  The quasi-biennial oscillation (QBO) began it westerly phase in JUN and has yet to reach its peak suggesting the PV stays intact.

Of course ... if a SSW comes to fruition ... it takes time for the initial wave to reach 10 mb and then propagate to the surface on average about three weeks later making the 'if and when' of it all wait until late JAN.