Winter '21 / '22 - Pacific Decadal Oscillation (PDO): OCT-21

 -3.06 (~2.25-sigma below the monthly mean)

PDO/s cool phase continues apace.  22 continuous months with an index value < 0 (JAN-20 - present).

Leading analog years
Winter / ENSO (MEI) / QBO
99-00 / C / W
08-09 / C- / W
62-63 / C- / E
75-76 / C / W
55-56 / C / -

All PDO analog years happened during a La Nina; however ... only one winter ('62 / '63) had QBO-E (D-J-F AVG:  ~ -16).

Winter '62 / '63
D-J-F Index Averages
NAO: -1.467
AO:  -1.914

Select season-total snowfalls  / P-O-R-N (inches)
RIC - 16.9 / 12.5
RNK - 29.7 / 19.5
DCA - 21.4 / 15.6
PHL - 20.5 / 22.1
NYC - 16.3 / 28.7
BGM - 95.3 / 83.7
BTV - 72.6 / 80.8
BOS - 30.9 / 43.7
CAR - 147.5 / 115.6

PDO < 0 (cool water along NOAM/s west coast) is associated with a longwave trof over NOAM/s west coast + above normal 500 mb geopotential heights over the SE CONUS + mild eastern U.S. winters.  La Nina is also associated with 500 mb ridging over SE CONUS.

These conditions more often than not mean a warmer than normal winter with below normal snowfall over at least the southern half of the forecast area but there have been notable exceptions to those rules.

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 '21 / '22 - Eurasia Snow Cover: OCT-21

Observed:  10,671,792 km^2
Average:  10,310,000 km^2
Median:  10,130,000 km^2

3.5% (5.3%) above normal (median)
Rank:  19 (n = 54)

Above average snow cover observed in 10 of the past 10 OCTs.
At least 1 standard deviation above normal snow cover in 5 of the last 10 OCTs.

Top Analog Winters (weight) / ENSO state / QBO state
1 - 2009/10 (2x) / W / E
2 - 2001/02 (2x) / nada- / W
3 - 2020/21 (1x) / C / W
4 - 2019/20 (1x) / nada+ / E
5 - 2015/16 (1x) / W+ / W

These analog winters have questionable predictive value b/c a moderate La Nina (C) and QBO-E are expected to prevail during Winter '21 / '22.

Blue markers located between the inner and outer circle have a weak yet statistically significant (p <= 0.05) positive correlation between Eurasia/s OCT areal snow cover and a forecast station/s season-total snowfall.  Strongest correlations found in New England where correlations range between 0.269 (BTV) and 0.376 (ORH).

A paultry ~16% of the variability (R2 = 0.158) in combined season-total snowfall from all forecast stations is explained by Eurasia/s OCT areal snow cover. 

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Period-of-Record:  1967 - 2021 (1969:  no data)
Data courtesy Rutgers Global Snow Lab

Previous posts about Eurasia's OCT areal snow cover here.