Sunday, May 17, 2009

Climate of Washington State

It's time for state #2 of my climate series, which is Washington. But before we start, let's recap the most recent poll.

Ever officially studied meteorology? We had 82 votes. And the results follow...

  • Yes, took some classes in college -- 19%
  • Yes, I have a degree in it -- 10%
  • No, but I would like to -- 46%
  • No, just high school Earth Science -- 23%

    So the majority of voters have not had any official meteorology classes. If you ever want to wet your appetite and learn a little more about weather and climate, there are now several colleges that offer the intro classes online, including the one I graduated from -- Metropolitan State College of Denver.

    Now on to the climate of Washington state.

    If you want diversity, this is a state to get it.

    Washington has everything from rain forest to arid deserts in the rain shadow of the Cascades.

    Western Washington has an oceanic climate while the eastern half of the state has a semi-arid climate.

    There are a few factors that really dictate the climate of Washington.

  • the global circulation -- which includes a large semi-permanent area of high and low pressure over the northern Pacific Ocean
  • continental air masses of North America
  • Olympic and Cascade Mountain ranges

    Let's talk more about the semi-permanent areas of high and low pressure over the north Pacific.

    In the spring and summer months, high pressure tends to dominate the northern part of the Pacific Ocean.

    Air spirals around an area of high pressure in a clockwise motion. This keeps the prevailing wind direction over Washington from the northwest, bringing cool and usually dry weather to the region.

    The opposite happens in the fall and winter months when low pressure usually
    replaces the spring and summer area of high pressure over the northern Pacific.

    Low pressure has a counter-clockwise circulation of air around it.

    This switches the predominant wind direction for Washington state out of the southwest, which sends mild and wet storm systems through the region.

    Sometimes that flow of moisture during the fall and winter months can connect with the jet stream and come all the way from Hawaii. When this happens, it is often called the Pineapple Express.

    Below is a picture of this happening, taken right as a storm is getting ready to slam the Pacific Northwest.

    In the next blog, we'll dive in and explore precipitation patterns across Washington.

    1. We’ve lived in Washington State for about five years now (the northern Columbia Basin on Lake Roosevelt a.k.a. Columbia River). I have to say the weather here is nearly as diverse as that in Texas (During my career we lived in West Texas - Trans Pecos, and SE Texas 35 miles north of the Gulf and about the same from the Louisiana state line).

      I’ve found an easy reading though comprehensive book about the weather of the Northwest – The Weather of the Pacific Northwest by Cliff Mass. He teaches at Atmospheric Science at the University of Washington in Seattle. Well worth reading for those interested in this region of the country.


    2. Thank you so much for this presentation on Washington State. It is excellent and so informative.

      Sallie GIlmore

    3. Chris,

      One of the most interesting things about Washington State's weather and climate is the issue of microclimates.

      The Puget Sound Convergence zone is but one example, perhaps really not micro. The Banana Belt of the Sequim/San Juan Islands area deserves some talk.

      Here on the East side, I'm in the Okanogan Highlands (FY-1)and the range of precipitation and temperatures within just a few miles is amazing.

      Thanks for doing Tennessee where I was born, and then WA where I live.