Winter '11 / '12 - Eurasia Snow Cover - October

The latest monthly data from the Rutgers Snow Lab shows the observed areal snow cover over Eurasia was normal during October.

The chart's orange line marks the month of October's long-term average snow cover.  The dashed yellow lines are one standard deviation above or below the average.

From a statistical process control (SPC) perspective...little variation above or below the mean has occurred in the region since the early '90s.  The early '90s marked the end of a 'warm' convergence resulting from predominantly +ENSO and +PDO conditions in the tropical and extra-tropical Pacific ocean that began in the mid '80s.

Long range seasonal forecasting schemes based on autumnal Eurasia snow cover have received a fair amount of attention in recent years.  The working hypothesis centers around the idea that 'above normal' snow cover in this region during the early fall is a strong leading indicator of colder than normal winter surface air temperatures over the eastern CONUS.

These colder surface air temperatures are thought to be a consequence of upward propagating Rossby waves -- initiated by above normal Eurasia snow cover -- entering the stratosphere which...in turn...weakens or reverses the polar vortex (PV).  A weaken PV is a favorable condition for negative index values of the northern annular oscillations (AO; NAO) which generally lead to below normal temperatures and increased storminess over the eastern CONUS.

The current state of Eurasia's autumnal snow cover does not suggest the eastern CONUS will experience below normal surface air temperatures and/or increased storminess during the upcoming winter. 

Areal snowfall data courtesy Rutgers Snow Lab.