CONTEST STATUS - Last update: 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

Saturday, December 9, 2006

Waiting for -AO


Having arrived on the doorstep of the '06 / '07 winter ragged and disheveled with hearts shattered from past season/s disappointments...we look longingly and lovingly to the Pro METs whose vision of future events own us all.

How much for Philly?

While feasting on tales of warring indices...3-D mass fluxes...and seasonal anomalies...the Pros throw us a few scraps and bone or two to keep our interest...only to find the -AO won/t be coming today but it will surely be here tomorrow.

But when tomorrow comes...the Pros suddenly go blind and proclaim just because the -AO hasn/t arrived...they can/t see where their forecast is wrong and yet...if we just wait until tomorrow...then -AO will come.

If we/re stuck waiting for -AO...shouldn/t we just move along...but we wait anyway...knowing full well -AO may never come.

There was...and still is...a widely held expectation that the dominant planetary flow regime this winter would comport itself in such a way to produce net negative index values of the Arctic Oscillation (AO) and the AO/s first-cousin...the North Atlantic Oscillation (NAO).

So...how/s that forecast working out? AO this month to date is 1.55 sigma. NAO at 0.648 sigma.

As we moved into meteorological fall...the AO was about one-half sigma above the normalized monthly mean for September (0.606) and November (0.521). October was a different animal coming is just over one sigma (-1.029) below the mean.



The AO is a measure of polar vortex/s circulation. When the index is negative...the vortex is weak. This weakness allows arctic air to escape...some would say drain...into lower latitudes. When the three-week moving average index of daily values is positive like it is now and has been since the second week of November...the vortex is strong and arctic air is contained.

So what/s going on? What other index gives a measure of the polar vortex? QBO...perhaps?

The QBO has been red hot from the west since April. It/s eight months into its warm cycle with about five months to go before it flips east.

When QBO is anomalously strong from the west...as it is now and has been since May...it indicates the polar vortex is cold and strong...which is complementary...and more importantly...coupled to a positive AO index.


As long as QBO is west...seems to me we/re stuck until spring waiting for -AO.

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