Friday, March 29, 2013

Coldest Stretch of Smarch Since 1993

Our average temperature over the March 13-27 (15 days) is 44.4 degrees. We've averaged a lofty 4.6 degrees below that benchmark in the same timeframe.  It's not the coldest stretch of March, regardless of starting point, in a while...we've been colder in a 15 day stretch of March as recently as March 4-18, 2007, where the temperature in that timeframe was 37.7 degrees.

Just looking at March 13th-27th, this stretch of time has been anomalously cold by March standards.  Not coldest since 1960 type cold but it has been the coldest stretch for us since 1993 and eighth coldest since 1960.

The big difference between 1993 and 2013, of course, was a massive snowstorm that rocked much of the East Coast at the onset of the cold pattern twenty years ago...and this year, just teases of cold, sleet, snow, and all sorts of other slop. Our snowfall total during this stretch was just 1.1", a lot less than the foot of snow that fell in the '93 Superstorm.

The upper pattern in the past years where there's been significant cold is a bit different than the case this year.  The "average" of years where's been a significant March cold shot locally featured a strong trough in the East, with a ridge of high pressure over the Gulf of Alaska and a mild amount of high latitude blocking up near Baffin Island.  Not all years had this setup on their own but blended together you could see where the pattern would support cold in the East  given there's a limit on troughy cold in Alaska and the Arctic.

A snapshot of the pattern from Tuesday of this week featured that same trough in the East but the influence of arctic blocking this year is much higher than in the other years in the data set.  The Arctic Oscillation (AO) is likely going to approach a record this March for its influence on the pattern, which in turn supported a strong trough of low pressure across the Eastern US.

Regardless of where the influence is set up, the result is the same -- one of our colder stretches in a while and a lingering reminder of Old Man Winter.