CONTEST STATUS - Updated: SUN ... 07-DEC-14 @ 6:30 PM EST

Winter '14 / '15 - Snowfall Forecast Contests

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16th Annual 'Regular Season'
STORM #2
Synoptiscope in VCP32

STORM #1 (26/27-NOV-14):
FINAL results here

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14th Annual 'Season-total'
Forecasts here.
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Wednesday, December 7, 2011

Winter '11 / '12 - White Christmas Probabilities

Updated below

White Christmas in the US is defined as 1" on-the-ground on 25-DEC.  The criteria are different in other countries.

The probability of an event is determined by dividing the number of times something happened by the number of time it could have happened.  If there was a white Christmas five times over 20 years...the probability is 25% in any given year.

This NCDC map is a little dated b/c it's based on the old 1961 - 1990 period of climate normals.  Good enough for our purposes.

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Folklore predictions...
- A green Christmas; a white Easter.

- If there's thunder during Christmas week...
The Winter will be anything but meek.

- The nearer the New Moon to Christmas Day...the harder the Winter.   [ed.  - new moon is 24-DEC!]

- If Christmas day be bright and clear
There’ll be two winters in the year.

- Thunder in December presages fine weather.
[ed. - somewhat at odds with 'thunder during Christmas week]

- Like in December like all the year long.
[ed. - does this face forward or backward?]

UPDATE:
The NWS has updated their white Christmas probabilities map based on the current 30-year climo period between 1981 and 2010...


Note there is one fewer classes in the new map.  The '< 5%' class has been combined with the '5-10%' class into one '< 10%' class...which is not an improvement for snow crows living along the map's southern boundary. 

Also note the classes are not represented by equal sizes.  Some are 15%-points...some are 10%-points...some are less than 10%-points.

1 comment:

Anonymous said...

Sadly, I am old enough to recall that there was thunder on Christmas Eve and New Years Eve in 1965 in northern New Jersey some rookie, huh?). We were visiting there at the time (I never lived in the U.S. but I have visited at least a hundred times). Well, you can see what happened after that, a pretty good shot of winter in late January. -- Roger Smith