Winter '22 / '23 - An over-the-horizon look at early autumn's a priori climate conditions
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near Woodstock ... VT Marion Post Wolcott (1940) |
Snowfall forecasting contests for 27 stations across New England and the Mid-Atlantic regions ... since 1999
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near Woodstock ... VT Marion Post Wolcott (1940) |
"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 ...
-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
NOV: +2.54 🔥🔥🔥
Only two other NOVs had a higher index ('78 +3.04; '93 +2.56)
TL;DR This winter/s average NAO index expected to be positive ( >0 ).
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Analogs and weights for composites:
'03 / '04 (1)
'99 / '00 (1)
'91 / '92 (1)
'93 / '94 (1)
'15 / '16 (1)
Each analog's average NAO for D-J-F was > 0.
NAO/s analog winters are assessed against the upcoming winter/s expected states of:
- ENSO (MEI moderate - trending weak La Nina)
- QBO-W < 10
- PDO (cool)
We removed '03 / '04 ... '91 / '92 ... and '15 / '16 from further consideration b/c they were +ENSO winters. Winter '93 / '94 had QBO-E so it too drops out.
Winter '99 / '00 survives with its weak La Nina --- QBO-W < 10 ... and a cool PDO.
"The La Nina phase will reach quite a formidable strength at its peak but is expected to start to weaken towards spring 2021."
"Historically, the most typical effect of a La Nina is a strong blocking high-pressure system in the North Pacific."
"North America winter forecast looks fairly solid to be a classical La Nina type winter. Most of western Canada is to expect colder and snowier conditions, along with Alaska.
"The United States expects to see a “dipole” pattern or a “two-faced” winter. The Northern [sic] United States are expected to be normal to colder and wetter. This increases the chance of more snowfall, but more likely towards the western half, and less likely in the eastern parts.
"The Southern [sic] United States can slowly prepare for warmer and mostly
drier than normal winter weather. This however does not imply that [sic] no
cold front can reach the southern states. It just implies that [sic] in a La
Nina pattern, it is much less likely to get frequent cold fronts down to
the very south."
"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
Through a careful multi-variate analysis of key teleconnection
indices and the process of elimination ... we/ve settled on the '04 /
'05 winter as this winter/s leading analog for the Contest/s forecast area.
Bottom line up front:
- Temperature: near normal except below normal over far northern stations
- Snowfall:
Above normal - northern half of forecast area
Normal to below normal - southern half of forecast area
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Consensus of dynamic and statistical model outlooks
ENSO: La Nada+ (0.5°C < ENSO Region 3.4 SSTa < 0.5°C)
Current PDO state (OCT-to-MAR) < 0
2019 trend analysis
QBO: W (+) going E (-)
2x2 contingency table (Chi-SQ Test for Independence) AO NAO
If NOV AO < 0 then 71% probability D-J-F average AO < 0
If NOV NAO > 0 then 73% probability D-J-F average NAO > 0
The analog winter/s key features follow:
ENSO: +0.5°C (lowest threshold of weak El Niño)
MEI: La Nada+
QBO: W (+) going E (-)
PDO < 0
AO < 0
NAO > 0
EPO < 0
Contest stations' cumulative season-total snowfall: 1,446" (AVG: 1,095")
Winter '04 / '05 - 5H GPHa (l) & 2mTa (r)
Negative 5H GPHa - W & Negative 5H GPHa - E ==> Trof-W / Trof-E
Neutral 2mTa over east coast; negative 2mTa over New England
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Winter '04 / '05 monthly anomalies (D-J-F)
DEC '04 - 5H GPHa (l) & 2mTa (r)
Positive 5H GPHa - W & Negative 5H GPHa - E ==> Ridge-W / Trof-E
Negative 5H GPHa INVOF Greenland ==> NAO > 0
Positive 5H GPHa INVOF Gulf of Alaska & Positive 5H GPHa eastern ATL ocean ==> AO > 0
Positive 5H GPHa INVOF Gulf of Alaska & negative 5H GPHa INVOF Hawaii ==> EPO < 0
Negative 2mTa over SE and Gulf Coast
JAN '05 - 5H GPHa (l) & 2mTa (r)
Negative 5H GPHa - W & Positive 5H GPHa - E ==> Trof-W / Ridge-E
Negative 5H GPHa INVOF Greenland ==> NAO > 0
Positive 5H GPHa INVOF Gulf of Alaska & Positive 5H GPHa eastern ATL ocean ==> AO > 0
Positive 5H GPHa INVOF Gulf of Alaska & negative 5H GPHa INVOF Hawaii ==> EPO < 0
Positive 2mTa over SE and Gulf Coast; negative 2mTa over NE CONUS
FEB '05 - 5H GPHa (l) & 2mTa (r)
Negative 5H GPHa - W & Negative 5H GPHa - E ==> Trof-W / Trof-E
Positive 5H GPHa INVOF Greenland ==> NAO < 0
Negative 5H GPHa INVOF Gulf of Alaska & Negative 5H GPHa eastern ATL ocean ==> AO < 0
Neutral 2mTa over east coast; positive 2mTa over NE CONUS
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Key
5H - 500 mb
2mT - 2 meter temperature
2mTa - 2 meter temperature anomaly
GPHa - geopotential height anomaly
ENSO - El Nino Southern Oscillation
MEI - Multivariate ENSO Index
AO - Arctic oscillation
NAO - North Atlantic oscillation
EPO - Eastern Pacific oscillation
PDO - Pacific Decadal oscillation
CONUS - continental United States
INVOF - in the vicinity of
Pacific Decadal Oscillation (PDO)
composites of 500 mb (5H) geopotential height anomalies (GPHa) and
2-meter air temperature anomalies (2m Ta) for analog winters '66 / '67 ... '68 / '69 ... '90 / '91 ... '04 / '05 ... '17 / '18
Quasi-Biennial Oscillation (QBO)
composites of 500 mb (5H) geopotential height anomalies (GPHa) and
2-meter air temperature anomalies (2m Ta) for analog winters '78 / '79 ... '85 / '86
... '95 / '96 ... '99 / '00 ... '02 / '03.
La Nada or neutral ENSO comes in two flavors -
Cool (-0.5 < Region 3.4 SSTa < 0)
Warm (0 < Region 3.4 SSTa < 0.5)
Current consensus expects 'warm' La Nada for Winter '19 / '20.
Recent La Nada years by decade:
1967
1979
1981 ... 1982 ... 1986 ... 1990
1991 ... 1993 ... 1994 ... 1997
2002 ... 2004
2013 ... 2014 ... 2017
Eurasia/s areal snow cover for OCT-19: ~ 12,800,000 SQ-KM
24% above 52-year P-O-R-N (~10,300,000 SQ-KM)
27% above 52-year median (~10,100,000 SQ-KM)
Rank: 7th
3rd highest past 10 years
4 of past 20 years below median ('05 ... '07 ... '08 ... '11)
OCT-18: ~10,400,000 SQ-KM
OCT-19: 23% greater than OCT-18
Analog 5H composite ('80/'81 ... '08/'09 ... '12/'13 ... '14/15 ... '16/'17) ... as of OCT-19
Severe Weather Europe's (SWE) analysis of the solar cycle and ENSO analogs ...
Analog 5H composite ('78/'79 ... '85/'86 ...'95/'96 ... '99/'00 ... '02/'03) ... as of SEP-19
Eurasia/s areal snow cover for SEP-19: ~1,570,000 SQ-KM
Analog 5H composite ('53/'54 ... '54/'55 ...'59/'60 ... '97/'98 ... '14/'15) ... as of SEP-19
UPDATE: SEP/s NAO did not change the analog years other than to shuffle the 4th and 5th ranks.
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Analog 5H composite ('50/'51 ... '08/'09 ... '12/'13 ... '16/17 ... '17/'18) ... as of AUG-19