GEOG 3232 Blog II

Air masses 

Seattle is affected by Maritime Polar and Continental Arctic air masses in the winter, as seen in the diagram below. At times Continental Polar air may dip down into the region due to Rosby waves, leading to lower temperatures than average.

Source: https://ec.gc.ca/air/default.asp?lang=En&n=1F36EFBB-1&offset=4&toc=show

During the summer months, Seattle receives warm humid air from Maritime tropical air masses. The diagram below shows some influence from a Maritime polar air mass, but due to the mass retreating north, this would not have a substantial effect on the region. 

Source: https://ec.gc.ca/air/default.asp?lang=En&n=1F36EFBB-1&offset=4&toc=show

Current Weather

Due to Seattle's location along the Pacific coast, the city sees the beginnings of mid-latitude cyclones. Below is a recent warm front that has pushed through the Seattle region. 

 The warm front begins off the coast in the Pacific and pushes eastward.

 As the front impacts the coast it elongates creating the long warm front seen in warm occluded fronts.

Sourse: http://www.weather.com/weather/map/interactive/1/SEA:9:US?interactiveMapLayer=radar&baseMap=r

Eventually, this system will turn into snow on the windward side of the Cascades and dry on the leeward side. 

Changes in Surface Conditions

These images show the current status of the storm shown above (April 13th and 14th). The warm front occlusion front has passed with the cold front right behind it. 

Source: http://www.weather.com/maps/current

Source: http://www.physicalgeography.net/fundamentals/7s.html

This diagram shows the air flow and convergence/divergence currently pushing through Seattle and into the western United States. 

Unique Features

Olympic Rain Shadow

Due to the Olympic Mountains creating a barrier between Seattle and the Pacific, the amount of precipitation is much less than on the windward side of the Olympic Mountains. The diagram below demonstrates the amount of rain fall the state of Washington receives annually. 

Source: https://content.lib.washington.edu/cmpweb/resources/map-rainfall.html

Note: Seattle sits between two mountain ranges, it is on the leeward side of the Olympic Range and the windward side of the Cascades. Because of this "rainshadow" cast by the Olympics the Seattle region sees between 30 to 60 inches per year were surrounding areas can see upwards of 180 inches. Also note, the leeward side of the Cascades is a more traditional model. The eastern portion of Washington is very dry and has almost desert conditions. 

Works Cited:

"Average Annual Precipitation in Washington State." Olympic Peninsula Community Museum. University of Washington, n.d. Web. 14 Apr. 2015.

"The Georgia Basin – Puget Sound Airshed Characterization Report 2014."Government of Canada, Environment Canada. Government of Canada, 13 Feb. 2015. Web. 14 Apr. 2015.

Pidwirny, Michael, Dr, and Scott Jones. "The Mid-Latitude Cyclone." The Mid-Latitude Cyclone. University of British Columbia Okanagan, 07 May 2009. Web. 14 Apr. 2015.

The Weather Channel. The Weather Channel, 14 Apr. 2015. Web. 14 Apr. 2015.