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 - Eurasia Snow Cover: OCT

~ 11,000,000 SQ-KM

 

Under-performing all year ... 

6% above P-O-RN (~10,320,000 SQ-KM)
9% above median (~10,080,000 SQ-KM)
Period-of-Record:  53 years
Rank: 19th

2nd lowest past 10 years
16 of past 20 years above P-O-R-N

OCT-19:  ~12,700,000 SQ-KM
OCT-20:  14% less than last year

Eurasia snow analog years offer little if any guidance given this winter should have cool ENSO / PDO and QBO-W.

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P-O-RN ==> period-of-record normal

Data courtesy Rutgers University Global Snow Lab
http://climate.rutgers.edu/snowcover/index.php

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 '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 - 19th Annual 'Season-total' Snowfall Forecast Contest: FINAL Results

Congratulations to Herb @MAWS for his 1st Place finish.
Herb also placed first in '03 / '04 and '09 / '10.

Forecasters ranked by their Total Absolute Error (TAE)
The '%MPRV over PORN' metric indicates how well the forecaster did compared to climatology [(Period-of-Record Normal (PORN)].  The most skillful forecasts beat climatology 

RED ==> 75th percentile
WHITE ==>  interquartile range (>25th & < 75th percentiles)
BLUE ==> 25th percentile

Forecasters' stations with the lowest absolute error

Read more »

Winter '19 / '20 - Teleconnections

Speechless ...

Winter '19 / '20 - 19th Annual 'Season-total' Snowfall Forecast Contest: Preliminary STP Verification

Preliminary sum-total season snowfalls for the verification period 01-DEC-19 though 31-MAR-20 collected from monthly climate bulletins (CLMxxx; CXUS51 ... CXUS52).

One forecast station (4% of all stations) with bonus season-total snowfalls [more than Period-Of-Record-Normal (P-O-R-N)].
Rank ordered descending by percent of P-O-R-N.

Green ==> 75th percentile
White ==> Interquartile range (< 75th & > 25th percentiles)
Red ==> 25th percentile

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Please report any errors in Comments along with a link to the correct data.
FINAL results expected NLT SAT evening.

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Winter '19 / '20 monthly snow totals
DEC:  Winter '19 / '20 - Season-total Snowfall Forecast Contest: DEC Totals
JAN:  Winter '19 / '20 - Season-total Snowfall Forecast Contest: JAN Totals
FEB:  Winter '19 / '20 - Season-total Snowfall Forecast Contest: FEB Totals
MAR:  Winter '19 / '20 - Season-total Snowfall Forecast Contest: MAR Totals

Winter '19 / '20 - 'Season-total' Snowfall Forecast Contest: MAR Totals

MAR-20 snowfall summary by forecast station.
Rank ordered descending by percent of monthly period-of-record-normal (P-O-R-N).

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Green ==> 75th percentile
White ==> less than 75th and greater than 25th percentile (inter-quartile range)
Red ==> 25th percentile

Obs reported as 0.05" implies Trace

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MAR Forecast Station Highlights
No station observed more than 100% of its monthly normal snowfall.

Biggest losers (0")
PHL
BWI
ACY
DCA
RIC
SBY
RDU
ORF

P-O-R-N v. Observed (less than 15%)
PVD:  (6.8'' v. 0.4'')
IAD:  (3.5'' v. 0.05'')
NYC:  (4.9'' v. 0.05'')
EWR:  (5.1'' v. 0.05'')
BDR:  (5.5'' v. 0.05'')
ABE:  (6'' v. 0.05'')
MDT:  (6.5'' v. 0.05'')
BOS:  (8'' v. 0.05'')

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Season-total

MAR P-O-R-N contributes 184" (20%) toward the season-total snowfall (D-J-F-M) of 929".
MAR-20 observed snowfall:  66" (36% of P-O-R-N; 7% of season-total snowfall)

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Teleconnections

No contest-worthy storms in MAR.

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Winter '19 / '20 - Season-total Snowfall Forecast Contest: DEC Totals
Winter '19 / '20 - Season-total Snowfall Forecast Contest: JAN Totals
Winter '19 / '20 - Season-total Snowfall Forecast Contest: FEB Totals