Winter weather variability in the Olympic Rainshadow

For all you weather/climate people – and there tends to be quite a lot of overlap between climate geekism and plant geekism – I thought I’d offer some observations about life in the Olympic Rainshadow.  This afternoon as I was driving past some fields around Sequim I noted that some farmers are irrigating their crops already.  Yowsers – it’s only March 1st!  I’ve cut my grass once and it needs it again already.  It couldn’t feel any more different from last year at this time, when everything was still buried under the foot of snow that fell on Feb 26, 2009 and still hadn’t finished melting.  And last year it dropped to 21 degrees on March 10 – a temperature that now seems a world away!  And it had better be only a distant memory: last year at this time nothing was budded out that could have been damaged from 21 degrees on March 10.  This year everything is growing already, and 21 degrees on March 10 would destroy all kinds of stuff, especially tree fruit crops.

The thing I’m coming to realize is that the climate of the Olympic Rainshadow exaggerates, rather than smooths, the features and effects of broader regional and worldwide weather patterns.  It’s misleading to say it’s generally drier in Sequim all the time than Seattle.  When it’s warm and dry in Seattle, it’s much drier here.  In this year’s El Nino pattern the warming and drying effect typical of the region is further enhanced because all the storms tend to come at us from the south or south-southwest, and are not usually very strong, and because of their trajectory have no moisture whatsoever left for us directly to the north-northeast of the mountains.  Additionally, winds during such storms tend to blow from the southeast, resulting in further warming and drying due to compression as they blow off the leeward side of the mountains.

On the other hand, La Nina – and any period of time when we’re in a “La Nina-ish” pattern, such as last October and November – can be seriously wet around here.  This is because with the more westerly and even northwesterly origin of weather systems, the Olympic Mountains offer little protection for Sequim.  The rainshadow is less pronounced and tends to favor Everett or even Seattle, if they’re lucky.  Meanwhile in Sequim it can seriously pour, resulting in 2-3 times are usual rainfall for a given period, and bringing us up to the amount of rainfall you might experience in… you guessed it… a normal Seattle winter.

So the rainshadow doesn’t work like magic.  But hopefully El Nino years like this one will give plants that prefer warmer, drier winters the boost they need to survive the wetter ones.  And I know it’s been a record warm Jan-Feb everywhere throughout the region this year, but it’s certainly much drier here in Sequim right now than it is in Seattle.  We’ve had less than an inch of rain since the new year, and I’ll probably be watering outdoor potted nursery stock starting later this week.  I’m not complaining as it’s a nice change, but I seriously hope we get a good rain or two sometime later this spring.

The Desert Northwest, February 26, 2009.  The plants are under there somewhere!


2 Comments (+add yours?)

  1. Randy/GA
    Mar 06, 2010 @ 13:07:00

    ian, interesting winter over many parts of the usa this season.check out the top five flips on, there were some crazy conditions. as for the weather geek/plant geek connection…. my guess is that weather/climate affects so much of plant growing it is almost necessary to have an awareness of your local growing and all its quirks. glad you are enjoying the mild nice weather. as for here i hope all the above normal rain from el-nino is past, and am ready for some WARMTH!


  2. desertnw
    Mar 06, 2010 @ 22:45:09

    Looks like it’s supposed to get cold up here next week – maybe that means warmer weather is coming to your area! Ian


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