CONTEST STATUS - Last update: THU ... 20-APR-17 @ 9:40 PM EDT

Winter '17 / '18 - Snowfall Forecast Contests

19th Annual 'Regular Season'

17th Annual 'Season-total'

Winter '16 / '17 - Snowfall Forecast Contests
18th Annual 'Regular Season'
FINAL results here
16th Annual 'Season-total'
FINAL results here

Tuesday, November 20, 2012

Winter '12 / '13 - North Atlantic Oscillation - November As Oracle

As it turns out...there/s a strong association between the sign of November/s monthly NAO index and the sign of the average NAO index during meteorological winter (D-J-F).  It's strongest when NOV/s NAO index is positive.

A chi-square test on NOV/s monthly values and average value of winter/s NAO suggests the sign of NOV/s NAO has a measure of predictive skill.

The 2x2 contingency counts the number of events when the the sign of winter/s NAO matched the sign of NAO in NOV.

The distribution of events offers these probabilities:
70%  + NOV ==> + Winter
30%  + NOV ==> - Winer

43% - NOV ==> + Winter
57% - NOV ==> - Winter

If the signs of NOV/s NAO and winter/s NAO events were independent / unrelated...then the distribution of events would follow a normal 'bell' curve where...
Positive NOV and positive (negative) winter:  15 (12) events
Negative NOV and positive winter (negative):  19 (16) events
The 2x2 contingency analysis reveals the sign of winter/s NAO is not independent (3.1% chance of Type I error) from the sign of NOV/s NAO.

As a footnote...OCT/s NAO has no 'predictive' value b/c it is independent from the sign of winter's NAO.

CPC/s monthly NAO index here.

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