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) |
-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
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NEWxSFC/s Director of Season-total Snowfall Forecasting |
Verification:
NWS climate reports (CLM or CF6)
Low. Score. Wins.
Deadline for entries: MON ... 30-NOV-20 @ 11:59 PM EST (01-DEC-20 @ 4:59 UTC)
Visit the Contest's website to enter your forecast.
Follow the link at the top right corner of the page to 'Enter Season-total Forecast.'
Update your forecast as often as you want prior to the deadline.
Only your last entry gets verified.
Thread updated periodically as new outlooks and forecasts become available from a variety of credible sources.
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CDC - NOV ...
Analogs and weights for composites:
'70 / '71 (24)
'07 / '08 (5)
'88 / '89 (1)
'95 / '96 (1)
'64 / '65 (1)
MEI analog data table (unranked)
Analog statistic (not shown): sum of squared errors
The MEI is based on five variables:
Sea level pressure (SLP)
Sea surface temperature (SST)
Surface zonal winds (U)
Surface meridional winds (V)
Outgoing Longwave Radiation (OLR)
Analogs and weights for composites:
'61 / '62 (2)
'91 / '92 (0)
'95 / '96 (0)
'99 / '00 (1)
'03 / '04 (0).
Two analogs averaged < 0 over D-J-F
Three analogs averaged > 0 over D-J-F
Little in the way of consensus which isn/t especially unusual for analogs.
We assess NAO/s analog winters with the upcoming winter/s expected states of ENSO (moderate-to-strong La Nina) ... QBO-W ... and (cool) PDO.
Recall ... '95 / '96 of 'Storm of the Century' fame was one of the better winter/s evah; however ... despite its weak La Nina profile ... its QBO-E and warm PDO eliminates the strongest calculated match for Winter '20 / '21 from the running. Analog weight: 0
'91 / '92 drops out as well b/c its winter had a strong a El Niño ... QBO-E ... and a warm PDO. The '03/'04 La Nada winter doesn't make the cut either. Analog weights: 0
The two remaining winters '61 / '62 and '99 / '00 are strong analogs for Winter '20 / '21. Both were moderate La Nina (per MEI) ... QBO-W < 10 ... and a cool PDO. '61 / '62 set snowfall records in more than a few stations. Analog weight: 2
Season-total snowfall for '99 / '00 was above average for southern mid-Atlantic stations and generally below average elsewhere. Analog weight: 1
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The 500 mb and 2m T weighted analyses below are based on the winters of '61 / '62 and '99 / '00.
North Atlantic Oscillation (NAO) analog composites of 500 mb (5H) geopotential height anomalies (GPHa) and 2-meter air temperature anomalies (2m Ta) for Winter '20 / '21.
5H GPHa weighted-composite
Main features:
La Nina ridge over SE CONUS
-PNA
Positive geopotential height anomaly south of Greenland ==> -NAO (??? lo-lat action center)
Storm track across northern CONUS
2m Ta weighted-composite
Main features:
Above normal temperature across the Deep South and SE CONUS
Cold AK ==> warm East
Analog years and weights for composites:
'89 / '90
(3) ... '90 / '91 (2) ... '97 / '98 (2) ... '02 / '03 (1) ... and '15 / '16 (1).
Arctic Oscillation (AO) analog composites of 500 mb (5H) geopotential height anomalies (GPHa) and 2-meter air temperature anomalies (2m Ta) for Winter '20 / '21.
5H GPHa weighted-composite2m Ta weighted-compositeAO analog data table (unranked)
"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."
NOV-19 NAO: +0.28
NOV-19 AO: -1.193
Same analog years as those associated with AO/s OCT-19 analysis but with a shuffled ranking.
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
Multivariate ENSO Index (MEI) composites of 500 mb (5H) geopotential height anomalies (GPHa) and
2-meter air temperature anomalies (2mTa) for analog winters '53 / '54 ... '59 / '60 ... '69 / '70 ... '80 / '81 ... '90 / '91.
Thread updated periodically as new outlooks and forecasts become available from a variety of credible sources.
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CPC ...
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.
Arctic Oscillation (AO) composites of 500 mb (5H) geopotential height anomalies (GPHa) and 2-meter air temperature anomalies (2m Ta) for analog winters '53 / '54 ... '54 / '55 ... '59 / '60 ... '97 / '98 ... '14 / '15.
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
Analog 5H composite ('80/'81 ... '08/'09 ... '12/'13 ... '14/15 ... '16/'17) ... as of OCT-19