Weather Blog

Grading La Nina so far: I give it a B-

Grading La Nina so far: I give it a B-
Despite driving snow, mailman John Jackson walks his route, Wednesday, Feb. 23, 2011, in Tacoma, Wash.

A former mayor got in some hot water by giving out a "B" grade in relation to weather when the masses thought something a little lower was in store, but I'm going to tread the same waters and give a passing grade so far to this winter's La Nina.

But before you break out the pitchforks and... I don't know what else, pitchforks are pretty effective... give me a chance to defend the grade.

First of all, let's talk about what criteria La Nina is supposed to be graded on. La Nina winters are usually marked by cooler and wetter than normal autumns and winters in the Pacific Northwest, with a lean toward the wetter part in Oct-Dec and the colder part Jan-March. (No, that is not revisionist history. You can find several online examples that La Nina is usually wet early then cold late.) The other calling card is a much greater than average mountain snowpack.

La Nina years do, by proxy, feature snowier than normal winters in Seattle, but it's usually a byprodcut of said cooler and wetter than normal conditions.

So, let's see how we're doing:

Autumn Rains: A

October had 5.24" of rain, over 2" above average. November was just a smidge under normal at 5.05", but December had 8.69" of rain, good for a Top 10 all time finish. Overall, October to December was 4.26" above normal, or about 29% above normal. Good La Nina signature.

Winter Rains: C+

As we got into January, the rain fall has tapered off a bit. January was about normal with 4.99" of rain, just under the normal of 5.13". But February just finished up with 3.05 -- more than an inch (1.13") below normal.

Autumn Temperatures: C

While we said the cooler than normal pattern is usually reserved for winter, autumn was a mixed bag. October was about average but November was a good 2 degrees below normal. On the flip side, December was quite warm -- matching November's average temperature of 43.2 degrees which was 2.5 degrees above normal.

Winter Temperatures: B+

January was slightly warmer than normal at 41.8 degrees -- just under a degree (0.9) above normal.

However, February was much colder than normal -- 39.25 degrees for average, a full 4 degrees below normal and good for seventh-coldest on record at Sea-Tac Airport. And long range models suggest March will continue the cool trend.

Mountain Snowpack: A- (and rising)

What a difference a few weeks make. On the Feb. 15 snow pack measurement, Mt. Baker, Crystal, and Paradise were pretty close to normal, but Snoqualmie was only running at 59% of normal, while Stevens was at 66% and Stampede Pass at 46%.  Very much thumbing its nose at skiers who were banking on La Nina's promised healthy snowpack.

But major snows in late February have helped catch up. March 1 data now shows snowpacks generally running 100-120% of normal. Snoqualmie is at 107% while Stevens is at 102% and Stampede Pass was at 89%. Mt. Baker is now up to 115% of normal and Crystal Mountain is at 135%.

Incidentally, that too is a calling card of La Nina years that the snowpack really ramps up as we get into late winter and early spring.

In fact, the year Mt. Baker broke the national annual snow record in the La Nina year of 1998-99, it was lagging behind in mid-late January as we were this year, only to get a mother-lode of snow in the late winter and spring, as we are in the midst of now.

(Although we are now way behind 1999's pace. Back then, Mt. Baker had 296" of snow; this year we're at 172".)

Lowland Snow in Seattle: D (although outside Seattle? I'll give it a C+).

Officially, through March 1, Seattle has received 7.8" of snow this season (at Sea-Tac Airport. I'm sure Downtown was much less -- probably about 3".) That is below the seasonal average of 11" of snow a year.

Living up to the hype: F

It's that previous statistic about lowland snow in Seattle that doomed La Nina in the eyes of many. Never mind that if you ask a climatologist, La Nina is going along mainly to script. A few bobbles but no two La Ninas are alike and there are several other factors in play that determine a winter pattern than just La Nina / El Nino.

As Cliff Mass brilliantly explained La Nina is more of a weighting of the dice, not a guarantee of a snowy winter. And ask anyone in Mount Vernon if they've had enough snow this winter.

But excitement built mainly because La Nina was so strong so early, and that previous winters where there was a rapid switch from El Nino to La Nina that ended in an intense La Nina were pretty snowy. That got the hype machine going (although for the record, there were voices of reason, even as early as October! :) )

As it turned out, the atmosphere did deal out some incredible stretches of winter weather this season that would have rivaled some of those past epic Northwest winters -- only they weren't positioned over the Northwest this time around.

The first extended icy grip went into northern Europe, which had one of their worst blizzards and snow stretches ever. Then it shifted to the East Coast of the U.S. where seasonal snowfall records were falling with the mounds of flakes. Meanwhile, both of those extended cold periods set up relatively mild patterns over the Northwest (because big, deep troughs will push up strong ridges on the edges) for long periods at a time (like, January.)

The pattern finally shifted toward the end of February to give us our extended cold period -- a period we're still in as of March 1 as Seattle is in the midst of 14 consecutive days below normal -- but with the later time on the calendar, we're not as cold as we could have been had this been 4-6 weeks earlier. Plus we were just short of a major snow event in early January but the storm took a turn to the north and that 200 mile difference meant a week of rain instead of relentless snow.

But still, years from now, an emotionless statistical analysis of this La Nina winter will probably rank it semi close to a normal event -- perhaps a little disappointing due to the early strength of the episode, but the season has reached most of the hallmarks of a La Nina winter, even if it didn't bury Seattle in 2 feet of snow or freeze over Green Lake every other week.

What did you think?

I posed a similar question on my Twitter and Facebook pages asking you to rate La Nina this year and as expected, it wasn't close to a B-. Those of you on Twitter, on average, gave it a C- and not one of my Tweeps gave it an A.

On Facebook, it was even more brutal, averaging a D+, although a Burlington judge gave an A+ (what with their 20+ inches of snow and buried cars last week) and a Federal Way FB'er gave an A-. But lots of Ds and Fs, including a very disappointed snow fan who wanted to give an F with seven minus signs. (I can only imaginge the force that minus key was getting as they typed it in: "F minus, minus, minus, Minus Minus MINUS....MINUS!!!")

Feel free to continue the conversation on those pages, and in the meantime, hang in there -- sometimes March can have a few tricks up its sleeve!