CONTEST STATUS - Updated: SAT ... 18-JAN-20 @ 1:15 PM EST

Winter '19 / '20 - Snowfall Forecast Contests
21st Annual 'Snow Storm' Snowfall Forecast Contest

Snow Storm #2
Synoptiscope in VCP32

Snow Storm #1 (01-DEC-19)
FINAL Results here

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19th Annual 'Season-total' Snowfall Forecast Contest
Deadline for entries has passed
Verification period: 01-DEC-19 through 31-MAR-20
The Forecasts here

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Winter '18 / '19 - Snowfall Forecast Contests
20th Annual 'Snow Storm' Snowfall Forecast Contest
FINAL Results here

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18th Annual 'Season-total' Snowfall Forecast Contest
FINAL Results here
Forecaster verification table here

Sunday, December 15, 2019

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

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