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Angeles in the Olympic Rain Shadow?
That is an interesting question, and one whose answer certainly has a major
impact on the weather in Port Angeles. To answer this we need to look at
how much rainfall and sunshine Port Angeles receives and compare that to
locations we know are in the rain shadow and locations we know are not. It is
also important to look at seasonality, as the rain shadow typically forms during
the winter and spring months.
In terms of precipitation, Port Angeles receives 25.57” of precipitation on
average, compared to 35.86” in Seattle , and 16.51” in Sequim.1
Despite the large difference in precipitation, our sunshine results surprised
us, indicating that Port Angeles has a climate that is quite similar to
Sequim’s, is dramatically brighter than Seattle’s, and is definitely in the
Olympic Rain Shadow! Here are the annual sunshine totals. 2
Annual Totals: October 2010-September 2011
The table above shows that
during the study period, Port Angeles exceeded Seattle in number of bright sunny
days by 45 % (128 vs. 88), and had 21 % fewer cloudy or dreary days (126 vs.
160). In terms of total recorded solar insolation, Port Angeles exceeded Seattle
by 12%. Clearly Port Angeles is dramatically brighter than Seattle and on an
annual basis has nearly the same sunny days as Sequim. For a better
understanding of the situation, let’s look at some seasonal totals.
During the winter months, Port Angeles recorded
more than 4X the bright sunny days of Seattle (16 vs 4), and fewer total cloudy
and dreary days (48 vs. 53). However Sequim had more bright sunny days than Port
Angeles, and dramatically fewer really dark and dreary days.
During the spring months, Port Angeles and Sequim recorded a very similar number
of days with at least partial sunshine, and similar numbers of cloudy days, with
the primary difference being more bright sunny days for Sequim.
However, in the brightest months of the year, Port Angeles took the lead with
more bright sunny days (55 vs. 43). The difference in summer sunny days is
likely due to the relative absence of maritime fog at the slightly higher
elevation location of the sensor in Port Angeles.
Port Angeles’ similarity to Sequim’s sunshine profile and its dramatic
differences from Seattle’s, especially in Winter, place it clearly in the
Olympic Rain Shadow.
We also have archived
monthly rain shadow climate
summaries and individual monthly reports with daily sunshine charts
and radiation plots, which look at Port Angeles conditions in more detail.
Rain Shadow Annual Days of Sunshine Report to view
a summary of Sequim vs. Seattle sunshine, with more detailed analysis, links to
monthly reports, and and study methodologies.
1 Precipitation data from the Western
Regional Climate Center,
2 This study is only over the one year
where radiation data is available, but since we are most interested in the
relative sunshine, not the absolute sunshine, we are not overly concerned
whether 2011 was an especially wet year. In fact in some regards, the wetter the
year, the better the year for studying the rain shadow, since it only forms
during stormy periods. Still, though as more data becomes available, we will
continue to track things.