Section II: Seattle Overview

The city of Seattle is located in a combined mountainous and coastal region. Seattle is surrounded by Puget Sound, Lake Washington, the Olympic Mountains and the Cascade Mountain Range. The weather station to which this blog pertains is located at the Seattle Tacoma International Airport in Washington. SeaTac is approximately 4.0 miles from the shore of Puget Sound. It is positioned at 47.4444 degrees of latitude and -122.3138 degrees of longitude and is at an elevation of 112.8 meters. This weather station hosts the official Seattle weather and climate records. The data records for this location began in 1944 and continue to the present.
 

This map shows the relationship between Seattle, Puget Sound, Lake Washington, the Olympic Mountains, and the Cascade Mountains. The Olympic Mountains protect Seattle from the majority of Pacific storms. Puget Sound and Lake Washington provide Seattle with a moist environment. Seattle is on the leeward side of the Cascade Range, meaning that Seattle receives a large amount of precipitation

Seattle Tacoma International Airport is located about 4.0 miles from Puget sound when a direct line is drawn between the two. SeaTac's proximity to Puget Sound could affect weather station readings and recordings based on humidity and moisture. It is surrounded by the tarmac of the runways, which could lead to higher albedo ratings and greater than state average temperatures.

 

In 2011, average monthly high temperatures at SeaTac ranged between 44.3 degrees Fahrenheit in December and 75.8 degrees Fahrenheit in August. The lows were between 34.0 degrees in December and 55.8 degrees in August. Due to Seattle’s proximity to the ocean and continentality (land heats and cools faster than the ocean and the ocean water is constantly being mixed), this area enjoys a moderate climate where temperatures do not fluctuate greatly.

 

 

This table from the National Climatic Data Center shows the average monthly and annual temperatures for Seattle in 2011. EMNT = Extreme Minimum Daily Temperature, EMXT = Extreme Maximum Daily Temperature, MMNT = Monthly Mean Minimum Temperature, MMXT = Monthly Mean Maximum Temperature, MNTM = Monthly Mean Temperature. This table shows that August was the hottest month and February was the coldest month in 2011.

This graph features the average monthly temperatures for the years between 1971 and 2000. As expected, in winter months the temperatures are cooler than in summer months. The range in temperatures is not very large, and highs and lows are typically within 20 degrees of each other.

 

Since Seattle is subject to continentality, precipitation is consistently distributed throughout the year. This precipitation typically comes in the form of rain, although on very rare occasions Seattle does get snow. In 2011, total precipitation per month ranged from 0.13 inches in August to 6.29 inches in March. The area received minor snowfall in February, a meager 3.00 inches. No month in 2011 was without of some form of precipitation.

 

 

This table from the National Climatic Data Center illustrates the average annual and monthly precipitation in Seattle, Washington

This graph shows the probability of 0.01" of precipitation monthly for the time period of June 6, 1948 to December 31, 2009. The graph shows that there is precipitation in the summer months, but the amount is significantly less than at other times of the year

The atmosphere of Seattle appears fairly stable. Fog crosses the land in the form of a marine layer, which indicates a stable atmosphere near a cool ocean current. Moist, stable air masses typically bring drizzle to Seattle. In general, the Olympic Mountains normally protect Seattle from severe weather. 

However, when the atmosphere becomes unstable, cumulus clouds form and create thunderstorms. Waterspouts have been spotted on Puget Sound, but not frequently. On Saturday, October 20^th, 2012 a waterspout formed on Puget Sound due to atmospheric instability. Turbulent winds in the upper troposphere combined with air from a polar maritime air mass met with a low pressure system off the coast of Washington and created cyclonic movements.
 

This is the waterspout which formed over Puget Sound due to an instable atmosphere. The waterspout was accompanied by extreme weather, including heavy rain, thunder, and lightning.

Other cases of severe weather include wind and ice storms. In January of 2012, Seattle experienced a severe ice storm which shut down travel for days. In 1962, severe winds blew across the west coast of the United States, devastating Washington, Oregon and California. The winds of the Columbus Day Storm, as the 1962 wind event was called, reached the equivalent of a category 3 hurricane.



This image is a recap of what the weather looked like on Columbus Day in 1942. There is a large low pressure cell off the northwestern coast of the United States. It is moving inland and meeting with a warm front. This is setting up an open occluded front. This brought high winds into the Seattle area, and all along the western coast.

Some of the damage from the Columbus Day storm included fallen trees, flipped planes, damaged homes and cars, and broken windows. Visitors of the Seattle Space Needle were evacuated, the progress of which was hindered by a stalled elevator. The 1962 Seattle World's Fair was obliterated.

Seattle is in close proximity to the Pacific Ocean and Puget Sound. It is not in a rain shadow and receives a fair amount of precipitation. Seattle most likely has a low Bowen Ratio due to the amount of moisture in the area. Seattle’s topography is similar to that of South America’s western coast, but has a little more water in the surrounding area. Based on the fact that all oceans combined have a Bowen Ratio of 0.11, and South America has a Bowen Ration of 0.56, a general estimate of Seattle’s Bowen Ratio would be 0.50.

Works Referenced

"Columbus Day Storm of 1962." August 2010. Wikipedia.org. web. 18-23 October 2012.

"GEOG 3232 Weather and Climate." Autumn Semester 2012. lecture.

HAMweather. Climate for Seattle Sea-Tac Airport, Washington. 2003-2011. web.

Leach, Matthew. "Remembering the Columbus Day Storm of 1962, 50 years later." 12 October 2012. Pugetsoundblogs.com. web. 18-23 October 2012.

McNerthney, Casey. "Massive storm killed dozens 50 years ago Friday." 11 October 2012. Seattlepi.com. web. 18-23 October 2012.

National Oceanic and Atmoshperic Administration. National Climatic Data Center: Station Details Seattle Tacoma International Airport. 2012. web. 18-23 October 2012.

"Rare Waterspout Touches Down Near Everett." 22 October 2012. Kimatv.com. web. 18-23 October 2012.

"Salem Online History." 2005-2005. Salemhistory.net. web. 18-23 October 2012.

"When Does Summer Really Start in Seattle?" 6 July 2012. Komonews.com. web. 18-23 October 2012.