CONTEST STATUS - Updated: FRI ... 14-JUL-17 @ 8:30 PM EDT

Winter '17 / '18 - Snowfall Forecast Contests
19th Annual 'Regular Season'
Season starts when the first flakes start a'flyin'

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17th Annual 'Season-total'
Entries accepted between 01-NOV-17 and 30-NOV-17
Verification period: 01-DEC-17 through 31-MAR-18

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

Tuesday, December 8, 2009

Winter '09 / '10 - C-C-C-O-L-D December - Part Deux

Amplification of the long-wave patten over NOAM appearing more likely with every model run.

The long-advertised deepening of the Arctic Oscillation (AO) index to near record-levels...aided by on-going weak stratospheric warming event weakening the polar vortex... appears set to get under way the next day or two along with an off-the-chart...near record-setting rise in the Pacific-North American (PNA) index.  Essential ingredients poised to fall in place for a stormy end of the month.

The return-period for an AO index less than or equal to -5.0 is 3.9 years for a total of 32 days since 1950 with no days observed that low since OCT-02.  The record value of -7.433 was set 15-JAN-77.





The return-period for a PNA index greater than or equal to 2.5 is 5.6 years for a total of 24 days since 1950 and no days observed during winter.  The record value of 3.397 was set 24-SEP-08.



Week 2 forecasts show broad positive (negative) 500 Z anomalies over the North Pole (across the western Atlantic) a perfect inverse match to the AO's loading pattern.  Note the negative anomalies south of Alaska marking the position of the Aleutian LOW and an east coast CONUS storm track custom-made for Miller 'A' cyclogenesis.



Week2 positive sea-level pressure anomalies located at high latitude along the Prime Meridian and south-central Canada allowing arctic air to drain into low-latitudes creating a strong baroclinic zone along the Gulf of Mexico and SE CONUS coasts.

Daily teleconnection index values here.

Earth System Research Lab - Physical Sciences Division/s Week 2 Tercile Probability Forecasts here.

EDIT:  corrected dates of record AO and PNA index values

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