CONTEST STATUS - Updated: SUN ... 10-JAN-21 @ 3:45 PM EST

Winter '20 / '21 - Snowfall Forecast Contests
22nd Annual 'Snow Storm' Snowfall Forecast Contest

Snow Storm #2
Synoptiscope in VCP 32

Snow Storm #1
FINAL Results here

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20th Annual 'Season-total' Snowfall Forecast Contest
Deadline for entries has passed.
The Forecasts! here
DEC Snowfall Totals here

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Winter '19 / '20 - Snowfall Forecast Contests
21st Annual 'Snow Storm' Snowfall Forecast Contest
Season ended as quickly as it started.
No winner this go'round ... too few storms (minimum of three required)

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

Thursday, December 10, 2020

Winter '20 / '21 - North Atlantic Oscillation (NAO): Analog Composites of 500 mb Height and 2-meter Temperature Anomalies ... as of NOV-20

 NOV:  +2.54 🔥🔥🔥
Only two other NOVs had a higher index ('78 +3.04; '93 +2.56)

TL;DR  This winter/s average NAO index expected to be positive ( >0 ).

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Analogs and weights for composites:

'03 / '04 (1)
'99 / '00 (1)
'91 / '92 (1)
'93 / '94 (1)
'15 / '16 (1)

Each analog's average NAO for D-J-F was > 0.

NAO/s analog winters are assessed against the upcoming winter/s expected states of:
- ENSO (MEI moderate - trending weak La Nina)
- QBO-W < 10
- PDO (cool)

We removed '03 / '04 ... '91 / '92 ... and '15 / '16 from further consideration b/c they were +ENSO winters.  Winter '93 / '94 had QBO-E so it too drops out.

Winter '99 / '00 survives with its weak La Nina --- QBO-W < 10 ... and a cool PDO.

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Season-total snowfall over the forecast area for '99 / '00 was above average across southern mid-Atlantic stations and generally below average elsewhere.  RDU was notable for its 26".

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The 500 mb and 2m T weighted analyses below are based on the winter of  '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:
Positive geopotential height anomalies from the International Date Line to the Prime Meridian
Negative geopotential height anomalies cover 3/4 of the Arctic

2m Ta weighted-composite
Main features:
Positive temperature anomalies across the CONUS and Canada
Cold AK ==> warm East

NAO analog data table (not ranked)
Analog statistic (not shown):  sum of squared errors

2 comments:

Anonymous said...

I foresee a winter of odds and ends, no compelling trends, a bit of this and a bit of that -- the timing may be different, but 1964-65 comes to mind, that winter had a bit of every weather type you could imagine.

Somewhere in this kitchen sink sort of mixture there could be a big storm too, there are large energy peaks available. About half a dozen medium-sized storms almost certain, no blowtorch, brief intense cold, some very bland featureless periods too.

Too many conflicting signals for anything sustained to work out.

-- Roger Smith

TQ said...

certainly not looking like La Nina in the early going ...