What are those differences? The three that top our list are the PNA INDEX (Pacific-North American Index), the AO (Arctic Oscillation), the NAO (North Atlantic Oscillation) and La Nina or El Nino. Don't fret over the technical specifics of each index. Just realize that each one originating from different locations (Arctic, North Atlantic and the Pacific) has the capability of influencing storm tracks and intensity over northern Ohio. Long term trends are great but can we see day-to-day details within these indices?
Look at the daily plots for the AO, NAO and PNA for each of the last 3 Decembers: First 2008, 2009 then finally 2010. Notice the fluidity of each of the last December's daily index levels.
How did this relate to high temperatures? Below is the daily high temperature graph for December 2008, 09 and 10. Last year was consistently cold yet 2009 and 2008 had a lot of ups and downs with only limited cold shots.
What about December snows? Not much in the last 3 winters.
Will this December be as changeable as year's past. Will we have a December like 2010 with continuous cold? Will this December feature cold shots with some milder breaks? I will address that in the next post.
Meanwhile, I'll be cutting down my Christmas tree in the mud followed by stringing lights on my house in shorts!