Is There A Return Cycle To The Truly "BIG" Pacific Northwest Arctic Blasts?

NOTE: Steve Pierce wrote this Article!


Is There A Return Cycle To The Truly "BIG" Pacific Northwest Arctic Blasts?



"I was doing some quick number crunching recently and could not help but ponder the idea that after 20 years, we may be overdue for an "old school" type of Pac NW arctic blast, perhaps this coming winter. Why? Several factors. First, I continue to look (as do many folks lately) at the uncanny alignment of several major indices (PDO, ENSO, MEI, NPI, GLAAM, AO) lately pointing towards what could be a "greater than normal" chance of seeing at least one major Pac NW arctic outbreak this winter. Second, could there be a "return cycle" to these events? If there was, perhaps this winter will provide the proof? Third, a sun that continues at record low output levels for the third year in a row which could prove to be the "wild card" this winter."

Here are the event dates (1940-present) that occurred when all four of the following criteria were met;

1. High temperatures below 20 at PDX
2. Lows in the single digits at PDX
3. Strong east wind outflow from the gorge at PDX
4. At least 5" of snow at PDX

Event Dates Date High Low Snow Depth
12/31/1968 19 9 9
2/2/1950 18 -3 13
1/31/1950 16 -2 15
2/3/1989 15 9 6
12/30/1968 14 8 5

Return Frequency Distribution Jan 1950 to Dec 1968 = 19 years Dec 1968 to Feb 1989 = 20 years Feb 1989 to Winter 2010/11 = 22 years (Please see note #1 and #2 below).

Honorable Mentions
Note 1 - December 1990's arctic blast was close to being on this list, but it lacked minimum snow amount (5") at PDX.
Note 2 - We would be exactly 20 yrs from Dec 1990 to this coming winter had Dec 1990 met the minimum snow criteria.
Note 3 - February 1989 was the last time PDX recorded a single digit low temp.
Note 4 - Only 10 days in Portland Airport history (1940-present) recorded high temperatures below 20 for daytime highs.

The dates below get an honorable mention for meeting almost all of the criteria above.

12/20/1990
12/31/1978
12/18/1964
12/17/1964

Steve Pierce
Vice President
Oregon Chapter of the American Meteorological Society (AMS)
503-504-2075 (Portland)
e-mail: stevejpierce@comcast.net
web site: http://www.ametsoc.org/chapters/oregon/