Thursday, January 24, 2013

Cold Waves

Last winter didn't have any consecutive days of temperatures at 32 or below -- we dropped to (sub)freezing on four days but never in consecutive fashion.  Yesterday marked the second straight day of not hitting 32 and we'll probably end up with five days, perhaps six if Sunday doesn't get to 32, of highs below the freezing mark before we're done.  In terms of duration, this wave is a lengthier one as most of the longer cold waves around here only go three or four days at most but this wave does not match the one from January 2011.

The winter of 2010-11 featured a week of consecutive (sub)freezing temperatures -- generally around or a degree below freezing for many of the days in the streak but it was a streak of chill that was pretty lengthy considering most winters max out at three or four consecutive days of such chill.

There are three other noteworthy streaks around here in recent years -- February 2007 featured a week consecutive, including three straight days of 25 or colder before the Valentine's Day sleetstorm hit the region.  January 2004 featured nine consecutive days of 32 or below -- including four straight days where the high did not top 25.   Going back a bit farther, in the run up and after the Blizzard of '96, Philadelphia featured eight straight days of 32 or below in January and a seven day streak just four weeks later, including back-to-back days of highs below 20 in that seven day streak.

Two of the more noteworthy streaks in Philadelphia's history (since 1874) are 13 days, set in January 1893, and 12 days, set in February 1895.  During that lengthy streak in 1895, the high did not crack 20 on five straight days and we didn't get above 10 degrees on two separate occasions.  A five day stretch where the highs were 14, 9, 11, 9, and 18 in consecutive.  The 1893 streak was pretty bad as well -- highs in seven days out of eight did not break 20.

The longest streaks are 15 days, from January 1961 and February the 1979 streak we didn't hit 20 for six straight days.

Our streak pales in comparison to some of the historic and premodern cold but, compared to how mild the first half of winter had been, it definitely has been a cold, hard slap in the face.