Skip to content
Link copied to clipboard

Can’t shake this cold

March 24 is a chiller; twice is enough.

Only 16 times in 142 years has the official temperature in Philadelphia failed to above 40 on a March 24. Yet it happened Tuesday (high, 40, or 16 degrees below normal), and on March 24, 2014 (high, 36).

Last March finished 4.6 degrees below normal in Philly; this March is on a similar pace, sitting at minus-4.2 through Tuesday.

That's not all the Marches have in common.

We noted in an earlier post that the nation hasn't waited this long for its first confirmed tornado sighting in records dating to 1950, and the severe-storm season in general is often to an amazingly slow start.Similarly, the tornado season last year was slow to ripen.

IThat late-season lingering cold and the severe-storm lulls evidently are very much related.

Greg Carbin at the Storm Prediction Center, in Norman, Okla.,  said that the most remarkable characteristic of the last two winters has been the persistence of upper-air patterns.

To oversimplify, high pressure, or heavier air, has dominated the West, and lower pressure in the East. High pressure tends to suppress storms and allows heat to build; lower pressure, the opposite.

California has remained in a state of dryness that Carbin calls "scary."

Last winter was the second-snowiest on record in Philly, and generally cold in the East, as has been the case this year.

The cold east of the Mississippi has put something of a cap on the atmospheric instability and bottled up those warm, moist surges from the Gulf necessary for severe-storm outbreaks.

That assuredly will change as the sun overpowers the pattern, and Philadelphia could get a taste of the new regime on Thursday when thunderstorms accompany temperatures rocketing well into the 60s.

However, another chilly outbreak will follow, and as we've noted, the last eight weeks have been almost relentlessly chilly.

The National Ice Center didn't issue its final report on Midatlantic waterway icing until Monday.

"I would say that this was one of the most severe ice seasons in recent decades," said the Ice Center's Brian Jackson.  "To have so much ice lasting well into March is a rare occurrence."

And at the very least, to have cold linger this late into March is highly unusual, if not highly annoying.