CONTEST STATUS - Updated: SUN ... 17-FEB-19 @ 6:40 PM EST

Winter '18 / '19 - Snowfall Forecast Contests

20th Annual 'Regular Season' Snowfall Forecast Contest

Interim Standings, as of Snow Storm #3
Details here

Snow Storm #5
Possible 'Call for Forecasts' MON ... 18-FEB-19

Snow Storm #4
FINAL Results here

Snow Storm #3
FINAL Results here

18th Annual 'Season-total' Snowfall Forecast Contest
Deadline for entries has passed.
Forecasts here
Verification period: 01-DEC-18 thru 31-MAR-19

Winter '17 / '18 - Snowfall Forecast Contests
19th Annual 'Regular Season'
FINAL results here

17th Annual 'Season-total'
FINAL results here

Friday, September 15, 2017

Winter '16 / '17 - 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. 

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 '16 / '17 ... the leading analog was '08 / '09 followed by '51 / '52 ... '54 / '55 ... '74 / '75 ... and '11 / '12.  A qualitative assessment of the forecast's accuracy would rate the top four analog as 'poor' ... IOW ... useless.

Winter '08 / '09 NAO was negative to neutral trending positive into MAR; whereas Winter '16 / '17 was weakly positive trending moderate.  The closest analog ... on the basis of the NAO remaining positive throughout the three-month forecast period ... was ranked last ('11 / '12).

Conclusion:  Winter '16 / '17 NAO analogs showed little ... if any ... skill.

An alternative forecasting technique looks at the NAO's sign for any calendar-year's month preceding the pending winter as a potential leading indicator of the NAO's sign for 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 a positive signs than negative.

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

Period-of-record NAO data here.

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