Winter '17 / '18 - North Atlantic Oscillation (NAO) Analog Verification

The analog forecasting technique seeks similarities to the NAO state in the run-up to the coming winter with NAO run-up states of winters past.  Presented here is the verification of NAO analogs for the '17 /'18 winter.

The NEWxSFC method ranks analog years by their the sum of square errors (SSE) statistic.
Lower SSE errors ==> stronger analog

Constraining the number of analog winters for analysis to five is arbitrary.

North Atlantic Oscillation (NAO) Index Analog Forecast Verification

In the run-up to Winter '17 / '18 ... '90 / '91 was the leading analog followed by '94 / '95 ... '54 / '55 ... '04 / '05 ... and '02 / '03.  Winter '17 / '18 NAO started strongly positive ... strengthened through the heart of the season then crashed below zero following meteorological winter's end

 

A qualitative assessment of the forecast's accuracy would rate the analogs #2 ... #3 ... and #4 as 'poor' ... IOW ... useless.

 

OTOH ... analogs #1 and #5 mimicked the observed behavior of the NAO associated with a weak La Nina.  Moderate El Niño conditions prevailed during the winters of '94 / '95 and '02 / '03.

 

CONCLUSION:  The analog forecasting technique provided useful guidance for Winter '17 / '18.

  

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An alternative forecasting technique looks at the NAO/s 'sign' (i.e., positive or negative) for any calendar-year's month preceding the pending winter as a potential leading indicator of the NAO's sign for upcoming D-J-F period.

Results from a chi-square 'test for independence' infers a statistically significant relationship ... at the 95% confidence level and a p-value < 0.05 ... between NOV's NAO sign and NAO's sign of the upcoming D-J-F period.

IOW ... if NOV's NAO is negative (positive) ... then the average NAO state during the upcoming winter will also be negative (positive); although the classification model is stronger ... i.e., lower false alarm rate ... for the predictor's month with positive signs than negative.  This is opposite of the relationship found for the Arctic Oscillation (AO).

 

BOTTOM LINE:  If NOV's NAO is positive ... chances are good the NAO state will average positive during the D-J-F period.

 

NOV '17 NAO/s sign was zero (0) for the 1st time in the index's 68 year record.  The 2x2 contingency technique offered no useful guidance.

Winter '17 / '18 - 19th Annual 'Regular Season' Snowfall Forecast Contest: Season Summary and Historical Perspective

FINAL results here.

EIGHT contest-worthy storms this season ... one more than average.
The storm count tied for 6th place with four other Winters ('07 / '08 ... '08 / '09 ... '10 / '11 ... and '13 / '14).

Contest-worthy Storm Count by Month
DEC - 1 [25-DEC-17]
JAN - 2 [04-JAN-18; 17-JAN-18]
FEB - 2 [07-FEB-18; 17-FEB-18]
MAR - 3 [07-MAR-18; 12-MAR-18; 21-MAR-18]
TOT - 8

 

 

Verified forecasts

http://www.newx-forecasts.com/NEWxSFC_19/storms/storm1_verifications_25Dec17.htm

http://www.newx-forecasts.com/NEWxSFC_19/storms/storm2_verifications_04Jan18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm3_verifications_17Jan18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm4_verifications_07Feb18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm5_verifications_17Feb18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm6_verifications_07Mar18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm7_verifications_12Mar18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm8_verifications_21Mar18.htm

 

FINAL Results and Storm Summaries

http://www.newx-forecasts.com/NEWxSFC_19/storms/storm1_summary_25Dec17.htm

http://www.newx-forecasts.com/NEWxSFC_19/storms/storm2_summary_04Jan18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm3_summary_17Jan18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm4_summary_07Feb18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm5_summary_17Feb18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm6_summary_07Mar18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm7_summary_12Mar18.htm
http://www.newx-forecasts.com/NEWxSFC_19/storms/storm8_summary_21Mar18.htm

Interim Standings
http://www.newx-forecasts.com/interim_19/interim1.htm
http://www.newx-forecasts.com/interim_19/interim2.htm
http://www.newx-forecasts.com/interim_19/interim3.htm
http://www.newx-forecasts.com/interim_19/interim4.htm
http://www.newx-forecasts.com/interim_19/interim5.htm
http://www.newx-forecasts.com/interim_19/interim6.htm

 

 

Winter '17 / '18 - 19th Annual 'Regular Season' Snowfall Forecast Contest: FINAL Results

Under the ‘two-thirds’ rule … forecasters who entered at least SIX forecasts are included in this season's FINAL standings.

Full table with all other error statistics at the Contest/s web site here (direct link).
Individual forecaster's storm statistics here (direct link).

 

 

Best Forecasts by Storm

 

Top 10 Forecasts (Error statistic:  SUMSQ Z)

SUMSQ Error Z is the primary measure of forecaster skill (lower the better).
Accounts for the magnitude and distribution of the storm-total snowfall for all stations.

Top 10 Forecasts (Error statistic:  Total Absolute Error Z - TAE)

TAE Error Z is the secondary measure of forecaster skill (lower the better).
Accounts for the magnitude of snowfall at each station.
 

Top 10 Forecasts (Error statistic:  RSQ Z)

R-squared (RSQ Z) is a supplementary measure of forecaster skill (higher the better).

Accounts for how well the variability of the observed snowfall was accounted for by the forecast.

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Eighteen unique forecasters submitted a total of 2,582 stations forecasts.
Eight forecasters entered all 8 contests.
Three forecasters entered 7 contests.
The remainder entered fewer than six

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Hope to see y'all again next winter.
 

Winter '17 / '18 - 'Season-total' Snowfall Forecast Contest: Month of MAX Snowfall

BOS Red Sox Opening Day
14-APR-53

Forecast stations observing their MAX monthly snowfall during Winter '17 / '18 in ...
DEC - 0
JAN - 7 (CAR ... PVD ... ACY ... SBY ... RIC ... ORF ... RDU)
FEB - 0
MAR - 18 (all the rest)

Leaving aside for the moment the fact FEB has 28 days and all other snow-season months have 31 ... 72% of our forecast stations observed their highest monthly snowfall total in MAR -- yes MAR -- this season.

Climo finds most of the contest/s forecast stations (14) observe their MAX monthly snowfall in JAN.  MAX monthly snowfall happens in FEB at 10 of the remaining 11 stations with only BDL having its greatest monthly climo snowfall in DEC.

No station/s monthly snowfall climo reached its maxim in MAR which makes the winter '17 / '18 all the more remarkable.

Winter '17 / '18 - 17th Annual 'Season-total' Snowfall Forecast Contest: FINAL Results

UPDATE 2:  10:45 PM EDT ... FRI ... 06-APR-18

All better (I hope)

 

UPDATE:  10:15 PM EDT ... FRI ... 06-APR-18

Senior NEWxSFC forecaster Roger Smith was inadvertently omitted from the FINAL Results summary (operator error - Excel copy down mistake).  Fix in the works

 

 h/t Roger 'Eagle Eye' Smith

 

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 Complete station-by-station forecaster verifications at the Contest/s web site here (direct link)

Perfect forecasts
iralibov @ PVD (47")

Near misses (< 1" error)
Mitchel Volk
0.1" @ ALB (74.9")
0.2" @ PHL (29.8")
0.2" @ ORF (15.2")
0.3" @ CON (85.3")
0.4" @ NYC (35.4")

Any.wx
0.1" @ BDR (39.9")
0.5" @ BTV (81.5")

33andrain
0.1" @ IAD (11.9")
0.6" @ BOS (58.6")

iralibov
0.1" @ RDU (8.9)
0.6" @ BOS (58.6")

kevinmyatt
0.4" @ NYC (35.4")
0.4" @ RIC (12.4")

Brad Yehl
0.2" @ BDL (48.4")

donsutherland1
0.6" @ EWR (34.4")

MarkHofmann
0.8" @ DCA (7.8")

Smallest station forecast error yet percent error >= 10%
Mitchel Volk
11.1" @ PWM (91.1")
2.2" @ SBY (17.2")

TQ
11.1" @ PWM (91.1")

Any.Wx
11.1" @ PWM (91.1")

donsutherland1
16.5" @ BGR (109")

33andrain
8.9" @ ORH (88.9")

iralibov
10.2" @ ACY (34.2")

Roger Smith
2.2" @ SBY (17.2")

snocat918
1.6" @ BWI (15.4")

MarkHofmann
0.8" @ DCA (7.8")

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Season-total snowfall from all stations (1,234") came in 35% above the period-of-record normal (914").  Winter '17 / '18 ranks 4th among other Contest years since winter '04 / '05 ... the season when BGR and BGM were added to the station list.

Winter '17 / '18 - 17th Annual Season-total Snowfall Forecast Contest: Observed Snowfall Station Summary

Bonus snows for 84% of forecast stations.

 

RED: <= 25th percentile
WHITE: > 25th and < 75th percentile
GREEN: >= 75th percentile

Winter '17 / '18 monthly snow totals
DEC:  http://newxsfc.blogspot.com/2018/01/winter-17-18-season-total-snowfall.html
JAN:  http://newxsfc.blogspot.com/2018/02/winter-17-18-season-total-snowfall.html
FEB:  http://newxsfc.blogspot.com/2018/03/winter-17-18-season-total-snowfall.html
MAR:  http://newxsfc.blogspot.com/2018/04/winter-17-18-season-total-snowfall.html

Winter '17 / '18 - Coastal Teaser #4

UPDATE 2:  9 AM EDT FRI ... 06-APR-18
Not happenin'

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UPDATE:  7:30 PM EDT THU ... 05-APR-18
Not lookin'good.
Maybe a nice surprise lurks in the overnight runs.

Possible 'Call for Forecasts' in the AM.

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Snow Storm #9?

Should the present NWP trend continue ...
Call for Forecasts:  THU ... 05-APR-18
Deadline for entries:  10:30 PM EDT ... FRI ... 06-APR-18
Verification period:  12:01 AM EST ... SAT ... 07-APR-18 till TBD

Watch this space.

Winter '17 / '18 - Season-total Snowfall Forecast Contest: MAR totals

Station snowfall summary for MAR-18.
Rank ordered by percent of monthly normal.

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Green ==> 75th - 100th percentile
White ==> Less than 75th and greater than 25th percentile
Red ==> 0 - 25th percentile

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Teleconnection indexes and month-over trend (updated as they become available)
AO:  -0.941⇩
NAO:  -0.93⇩
PDO:  -0.05⇩
QBO:  -19.77⇩
SOI:  10.5⇧

Winter '17 / '18 - Snow Storm #7: NESIS

CAT 2
NESIS 3.15

Winter '17 / '18 - Coastal Teaser: #3

UPDATE:
SAT ... 31-MAR-18 @ 10 PM EDT

Nothing contest-worthy about this event ATTM.

Slightest chance the 00z ... 01-APR-18 NWP runs will suggest otherwise ==> possible SUN AM  'Call for Forecasts'.

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Snow Storm #9?

Should the present NWP trend continue ...
Call for Forecasts:  SAT ... 31-MAR-18
Deadline for entries:  10:30 PM EDT ... SUN ... 01-APR-18
Verification period:  12:01 AM EST ... MON ... 02-APR-18 till TBD

Watch this space.