Sunday, December 16, 2007

Contest # 2 - Teleconnections

Contest Storm #2 got no help from the PNA index as it was negative during the period. Positive PNA is frequently cited as an important ingredient for decent snowfalls in the NE CONUS. A positive PNA index doesn/t hurt b/c it oft times favors cyclogenesis off the SE CONUS coast...but it/s not an absolutely necessary ingredient.

LOW heights dominating the NHEMI polar region resulted in an above normal AO index as the s/w trof lifted NE into the forecast area. The index declined slightly while the event unfolded on Sunday.

The negative NAO index...currently @ nadir...was a likely consequence of the decaying Rex block over Europe with the westerly extension its trof axis INVOF the Azores rather than significant ridging over Greenland. The vortex over NE CN / Davis Straits was also a contributing factor.

The teleconnection indices associated with Contest Storm #2 offer more evidence that +PNA and -AO / -NAO are not prerequisites...as all too commonly presumed...for decent snows across the NE.

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