Monday, February 27, 2006

Climate: Postmortem on Meteorological Winter 2005-2006

by Tom Thunstrom

In Mid-January, I spoke of comparing this winter to 1936-1937 and said there were some similiarities between the two during the first six weeks of the winter. Since Meteorlogical Winter ends Tuesday night at midnight I figure I would get the postmortem written on the winter with regard to Philadelphia, seeing if the 1936-1937 comparison or analog held for the remainder of the winter.

While we still have 2 days left before we technically go into Spring, I wanted to revisit the performance of these two winters in comparison to what happened THIS winter temperature-wise. For the sake of comparison, I am including the 33-34 analog because it followed the prior record setting hurricane season of 1933. I am also including 1989-1990 because it was one of the better fit winters because of its cold December (colder than this past winters) and similiar warmer second half.

Average Temperatures (December):

2005-2006 34.40322581
1936-1937 39.61290323
1989-1990 25.4516129
1933-1934 36.20967742

Average Temperatures (January):

2005-2006 40.75806452
1936-1937 41.41935484
1989-1990 40.29032258
1933-1934 37.75806452

Average Temperatures (February):

2005-2006 36.25
1936-1937 35.85714286
1989-1990 41.16071429
1933-1934 22.19642857

Average Temperatures (Winter):

2005-2006: 37.1875
1936-1937: 39.06666667
1989-1990: 35.45
1933-1934: 32.38333333

Similiarities to the winters I mentioned and to this winter:

(1) 36-37 and 33-34 both featured Januaries that were their warmest month for meteorological winter.

(2) 36-37 and 33-34 featured February as their coldest climo month. Had we not had that snowstorm on December 9th, we might have been able to say the same thing about our February.

(3) 89-90 shares our winter's trend of having the coldest December.

The first graph shows all four of the winters together for trend purposes.

The second graph shows just 05-06 vs 36-37. While the six weeks between 12/15 and 2/1 were quite similiar between the two winters, February did not quite match and they almost had the exact opposite pattern (at least through yesterday). 36-37 went cold early, moderated around 2/8, cooled off again and then went mini blowtorch after 2/18, only to go cold at the end of the month. At the same time, however, the temperatures for the two months were not that far off.

Perhaps 36-37 isn't a bad analog to look at for the whole of winter? If you take out the first 15 days of December 05, here's how the four stack up:

December 16-February 26
1936-1937 38.54794521
2005-2006 39.82638889
1989-1990 37.00
1933-1934 32.19444444

If you can take the 'opposite' effect for 36-37's February vs this February out of consideration, the two winters were pretty similiar overall temperature-wise and I would certainly think 36-37 is at least worthy of some analog consideration in comparison to this winter.