Winter '22 / '23 - An over-the-horizon look at early autumn's a priori climate conditions

near Woodstock ... VT
Marion Post Wolcott (1940)

TL; DR

- The stars have yet to align for snow crows and other winter wx enthusiasts.

- Above-normal temperatures and below-normal snowfall for most NEWxSFC/s stations.

 

> Warranties neither expressed nor implied.

> User assumes all risk.

> Not intended for use by children.

 

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Decoder Ring

AO: Arctic Oscillation

CONUS: Continental United States

D-J-F: December-January-February

ENSO: El Niño - Southern Oscillation

EPO: Eastern Pacific Oscillation

M-A: Mid-Atlantic

NE: New England

NAO: North Atlantic Oscillation

NHEMI: Northern Hemisphere

NWP: Numerical Weather Prediction

PDO: Pacific Decadal Oscillation

QBO: Quasi-Biennial Oscillation

PNA: Pacific-North American pattern

SSTa: Sea-Surface Temperature anomaly

SSW: Sudden Stratospheric Warming

 

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To the extent ENSO ... QBO ... SSTa in the tropical Pacific and the NE coastal waters of CONUS ... sunspots ... PDO ... and the extent of Eurasian cover have any predictive value ... here laid upon the table is the current state of play heading into Winter '22 / '23 as divined from NEWxSFC/s Whirled Headquarters located east of the fall line in VA.

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Winter '18 / '19 - The Woolly Bear Caterpillar Guide to Winter Weather Forecasting

It/s that time of year again when long-range wx forecasters scour the bowels looking for ... well ... wadda you say we don/t go there.

More better ... consult the Woolly Bear Caterpillar Guide to Winter Weather Forecasting.

(Lightly edited re-post from USENET news group ne.weather 11-OCT-03)

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In recent weeks ... a spate of news articles have appeared about the woolly bear caterpillar and its legendary ability to foretell the upcoming winter based on the color and width of its black and orange stripes.

With so much good information scattered across so many sources ... there appeared to be a need to compile the forecasting rules.

This handy forecasting guide can be printed and kept inside your coat pocket for easy reference.

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The Woolly Bear Caterpillars Among Us

There is more than one kind of woolly bear caterpillar.  The one you use when forecasting is the banded woolly caterpillar ... which becomes the Isabella moth (Pyrrharctia Isabella) in the spring.  Pictures of the caterpillar and moth can be seen here: Caterpillar Moth

Science is Skeptical

It should come as no surprise ... entomologists pooh-pooh the very idea banded woolly bear caterpillars can predict future events.  These naysayers claim variations in band color and width are evidence of a worm/s age and the fall weather conditions when the worm reached maturity.

Worms exhibiting more black than orange are older and grew in wet conditions.  Worms exhibiting less black than orange are younger and grew in dry conditions.  And therein we find the caterpillar's predictive value. 

Read 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 - 20th Annual 'Season-total' Snowfall Forecast Contest: Call for Forecasts!

NEWxSFC/s Director of Season-total Snowfall Forecasting

Here comes winter with its oscillating Arctic and North Atlantic indexes ... sudden stratosphere warmings ... so-so ENSO ... and if we/re lucky .... an endless parade of 'Miller A' LOWs raking the eastern seaboard.

NE.Wx/s 20th Annual ‘Season-total' Snowfall Forecast Contest is the absolute best ... biggest ... and possibly ONLY chance to be recognized for your astute long-range forecasting acumen ;/

And it's s-o-o easy.
Cool prizes ... too!

All you have to do is issue the best forecast for the 'season-total' snowfall at 25 east coast stations between RDU and CAR!

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Forecast element:
season-total snowfall @ each station

Forecast period:
01-DEC-20 through 31-MAR-21

Error statistic: total absolute error
[Σ abs(forecast - observed)]

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.

Read more »

Winter '20 / '21 - Outlooks

Thread updated periodically as new outlooks and forecasts become available from a variety of credible sources.

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CDC - NOV ...

Read more »

Winter '20 / '21 - Multivariate ENSO Index (MEI): Analog Composites of 500 mb Height and 2-meter Temperature Anomalies ... as of SEP / OCT-20

 Analogs and weights for composites:
'70 / '71 (24)
'07 / '08 (5)
'88 / '89 (1)
'95 / '96 (1)
'64 / '65 (1)

 We assess the MEI analog winters with the upcoming winter/s expected states of ENSO (moderate-to-strong La Nina) ... QBO-W ... and (cool) PDO.

Seeing how statistical and dynamic models predict a moderate La Nina this winter ... '64 / '65 and '95 / '96 don/t match the expectation which leaves '70 / '71 ... '07 / '08 ... and '88 / '89 as problem children.

Two concerns about the utility of winters '70 / '71 ... '07 / '08 ... and '88 / '89 ...
Two analogs depict a late winter La Nina intensification (vice expected fade) ... all three had QBO - E contrary to this winter's QBO-W ... and sadly no composites nor forecast guidance. 

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)

Winter '20 / '21 - North Atlantic Oscillation (NAO): Analog Composites of 500 mb Height and 2-meter Temperature Anomalies ... as of OCT-20

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

NAO analog data table (unranked)
Analog statistic (not shown):  sum of squared errors

Winter '20 / '21 - Arctic Oscillation (AO): Analog Composites of 500 mb Height and 2-meter Temperature Anomalies ... as of OCT-20

 Analog years and weights for composites:
'89 / '90 (3) ... '90 / '91 (2) ... '97 / '98 (2) ... '02 / '03 (1) ... and '15 / '16 (1).

Sadly ... all analog years were +ENSO winters; not something expected this season so they're of limited utility.

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-composite

2m Ta weighted-composite

AO analog data table (unranked)
Analog statistic (not shown):  sum of squared errors

Winter '20 / '21 - Severe Weather Europe: Winter Forecast

 Severe Weather Europe ...

"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."

Winter '19 / '20 - North Atlantic Oscillation (NAO): Leading Analogs' 5H and 2mT Composite Anomalies ... as of NOV-19

NOV-19 NAO:  +0.28

Same analog years as those associated with NAO/s OCT-19 analysis but with a shuffled ranking.
Winter / AVG NAO
80-81 / 0.487
08-09 / 0.077
12-13 / 0.227
14-15 / 1.197
16-17 / 1.113


Weighted NAO Analogs for Winter '19 / '20:  5H GPHa (l) & 2mTa (r)

- Positive 5H GPHa over west CONUS & negative 5H GPHa over eastern third of CONUS ==> Ridge-W / Trof-E flow regime
- Positive 5H GPHa INVOF Azores ==> NAO > 0
- Negative 5H GPHa over North Pole ==> AO > 0
- Negative 5H GPHa INVOF Great Lakes and along East Coast ==> Miller B-type storms
- Negative 2mTa along East Coast and most of New England

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At the 95% confidence level ... the Chi-square 'Test of Independence' shows the state of NOV/s NAO and the average NAO state for the ensuing D-J-F period are not independent.  They are related and have predictive value.

Over the NAO/s 69 year period-of-record ... the data show when NOV/s NAO is positive  ... there's a 73% chance the winter/s average NAO will be also positive.

The present analog years add weight to the Chi-square analysis suggesting NAO/s average state this winter will be positive.  An important caveat:  four of the five NAO analogs years occurred during 'cold' ENSO winters.  Winter 14 / '15 was the exception with a weak El Nino (SSTa 0.6°C).  All forecast stations ... in total ... measured 50% above normal snowfall that winter.

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Key
5H - 500 mb
2mTa - 2 meter temperature anomaly
GPHa - geopotential height anomaly
CONUS - continental United States
INVOF - in the vicinity of
ENSO - El Nino Southern Oscillation
SSTa -  sea surface temperature anomalies

Winter '19 / '20 - Arctic Oscillation (AO): Leading Analogs' 5H and 2mT Composite Anomalies ... as of NOV-19

NOV-19 AO:  -1.193
Same analog years as those associated with AO/s OCT-19 analysis but with a shuffled ranking.

Winter / AVG AO
97-98 / -0.778
58-59 / -1.579
14-15 / 0.849
54-55 / -0.717
53-54 / 0.082

Weighted AO Analogs for Winter '19 / '20:  5H GPHa (l) & 2mTa (r)
- Negative 5H GPHa over Gulf of Alaska & Positive 5H GPHa INVOF Hawaii ==> EPO > 0
- Overall North American pattern mimics Tropic/Northern Hemisphere's (TNH) negative phase often associated with +ENSO.
- Negative TNH ==> 1)  stronger than normal Pacific jet farther south of its normal axis and 2) well above normal temperatures in eastern North America.
- Active sub-tropical jet
- Positive GPHa over eastern Canada would 1) advect cP flow from hi-latitude snow fields into the eastern U.S. and 2) weaken the Hudson LOW.

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At the 95% confidence level ... the Chi-square 'Test of Independence' shows the negative state of NOV/s AO and the average AO state for the ensuing D-J-F period are not independent.  They are related and have predictive value.

Over the AO/s 69 year period-of-record ... the data show when NOV/s AO is negative ... there's a 71% chance the winter/s average AO will be also negative.

The present analog years add weight to the Chi-square analysis indicating AO/s average state this winter will be negative.

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Key
5H - 500 mb
2mTa - 2 meter temperature anomaly
GPHa - geopotential height anomaly
EPO - Eastern Pacific oscillation
cP - continental Polar air mass
INVOF - in the vicinity of

Winter '19 / '20 - Leading Analog: Winter '04 / '05

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

Winter '19 / '20 - Multivariate ENSO Index (MEI) - Leading Analogs' 500 mb Anomaly Height Composite ... as of OCT-19

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.

5H GPHa composite
- Ridge-W / Trof-E
- Negative 5H GPHa INVOF Aleutian Is. & positive 5H GPHa INVOF Hawaii ==> EPO  > 0
- Azores-like positive 5H GPHa ==> NAO > 0
- Negative 5H GPHa / lo-latitude trof axis ==> active sub-tropical jet (STJ)

5H GPHa weighted-composite

2mTa weighted-composite

Read more »

Winter '19 / '20 - Outlooks

Thread updated periodically as new outlooks and forecasts become available from a variety of credible sources.

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CPC ...

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From WCVB Boston...
"More cold outbreaks. More opportunities for snowstorms here along the East Coast. This could be a very active winter" said Dr. Judah Cohen (AER)

"Cohen thinks this winter may get off to a slow start but make up for lost time later in the winter. A disturbance of the polar vortex sometime in December could make for a very cold January and February.

"Boston could receive about 59 inches of snow ..." said Cohen.

Read more »

Winter '19 / '20 - Severe Weather Europe: FINAL November Model Forecast for the Upcoming Winter

"Most forecasts are showing certain lower pressure in the North Atlantic, and higher pressure over Europe and USA, which means generally  milder winter. The forecasts are on the same trend since September, which is very rare.

"Across the Atlantic, models generally agree on potential northerly flows over NW and NE USA and E Canada, while central USA currently has lower chances for winter weather overall.

"We still have the stratosphere as a major factor. Long-range forecasts are generally not as good at forecasting stratospheric dynamics in detail, which means they tend to underestimate any potential sudden stratospheric warming events (SSW’s) since the final forecast is made out of many individual calculations, which have different ideas about the stratospheric development.

"An SSW event can have a major impact on the circulation and can cause major pattern changes in the Northern Hemisphere. So a potential SSW event is an important factor that can change the course of winter in either way across the North Hemisphere."

More from Severe Weather Europe ...

Winter '19 / '20 - Pacific Decadal Oscillation (PDO): Leading Analogs' 500 mb Anomaly Height Composite ... as of OCT-19

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

5H GPHa composite
 - Trof-W / Ridge-E
- High GPHa INVOF Aleutian Is. & low GPHa INVOF Hawaii ==> EPO < 0
- Azores HIGH ==> NAO > 0
- High GPHa dipole Azores & Aleutian Is. ==> AO > 0

5H GPHa weighted-composite

2m Ta weighted-composite

Read more »

Winter '19 / '20 - Quasi-Biennial Oscillation (QBO): Leading Analogs' 500 mb Anomaly Height Composite ... as of OCT-19

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.

5H GPHa composite
- Ridge-W / Trof-E
- Hi-latitude blocking over Greenland ==> NAO < 0

5H GPHa weighted-composite

2m Ta weighted-composite

Read more »

Winter '19 / '20 - Arctic Oscillation (AO): Leading Analogs' 500 mb Anomaly Height Composite ... as of OCT-19

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.

5H GPHa composite

- Overall North American pattern mimics Tropic/Northern Hemisphere's (TNH) negative phase often associated with +ENSO.

- Negative TNH ==> 1)  stronger than normal Pacific jet farther south of its normal axis and 2) well above normal temperatures in eastern North America.

- Active sub-tropical jet

- Positive GPHa over eastern Canada would 1) advect cP flow from hi-latitude snow fields into the eastern U.S. and 2) effectively displace the Hudson LOW from its climatologically favored location.

5H GPHa weighted-composite

2m Ta weighted-composite

Read more »

Winter '19 / '20 - 500 mb Geopotential Heights and 2m T Anomaly Composites: La Nada Years

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

5H GPHa composite - all La Nada years (n = 15)

Prevailing feature common to cool and warm La Nadas ...
- Positive 5H GPHa INVOF Aleutian Is. & negative 5H GPHa INVOF Hawaii = EPO < 0 ==> Arctic outbreaks into central CONUS

Read more »

Winter '19 / '20 - North Atlantic Oscillation (NAO): Leading Analogs' 500 mb Anomaly Height Composite ... as of OCT-19

Analog 5H composite ('80/'81 ... '08/'09 ... '12/'13 ... '14/15 ... '16/'17) ... as of OCT-19

- EPO-like ridge offset slightly to the west of preferred position for a 'Trof-East' regime
- Azores HIGH ==> NAO > 0
- Low geopotential heights over pole ==> AO > 0
- Negative height anomaly over southeast Canada favors primary storm track through the Upper Plains and across the Great Lakes in line with current soil moisture axis

Weighted analog 5H composite

Weighted analog 2m T composite

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