Monday, January 21, 2013

Perspective Reminder On Cold

Every so often when a more lengthy cold shot comes along, you hear talk of "coldest since 1994 or coldest in YEARS" hyped about from a headline chaser.  As you generally know if you follow this site, I'm not a big fan of that stuff for a litany of reasons.  While the incoming cold shot will be pretty cold by our standards of chill but it probably will be hard pressed to be coldest in several years.

It's hard to remember that last winter did, at times, bring some chill along for the ride while we spent days or weeks on end driving around with our windows open and enjoying "winter".  We had several January mornings where lows were below 20 degrees, including a 14 degree morning on January 4th.  Some computer modeling has hinted at lows in the mid teens in the city on our coldest of cold mornings in the coming week -- we could approach or even tie last winter's low water mark on temperatures.  However, to get coldest in several years you need to reach at least a low of 7 degrees in Philadelphia.

That, at least in the first blast of cold coming in through Friday, will not happen.  No snow cover of note nearby and even with a shot for a dusting of snow it's likely not enough to help induce the drop in temperatures needed to reach those depths.  Highs likely will be in the mid 20's, at worst, on our coldest days.  Again, not going to be "coldest in several years" cold but it will be cold.

How often do we deal with colder temperatures?  We have not had a winter where the high has been below freezing since 1997-98 (the Super Nino winter) and every winter since 2001-02 has featured a high below 30 degrees on at least one day.  Yes, cold happens around here although headline chasers may make us think 20's are apocalyptic and that glaciers are impending along I-95.

Over the last eight winters, we have had 103 days where we didn't get above 32 degrees.  That's an average of 12.9 per winter.  Five of the last eight winters had double digit days of 32 or below highs.  In fact, 2011 featured a week straight and 11 days in 17 where the high didn't break 32 degrees.

We could argue that the incoming cold shot will be the longest since 2011 in duration but in terms of intensity it may be pretty hard to out-do these lows from the bottom of the January 2011 cold shot, at least in the first round of cold coming in this week.  Modeling is hinting that we might approach 10 in the city next weekend for lows...if model hype is reality, we will approach the benchmark but it's still a swing and miss in being "coldest in several years" cold.

Keep that in mind when you hear or see someone bring up "shades of 1977, 1994, 2007".  January 2011's cold was impressive as well.  It's a shame it's being forgotten as conveniently as it is because January 2011 was one of the coldest months we have had to average since that February 2007 cold wave.