The Davis Instruments Vantage Pro 2 Plus with option solar sensor is located on the roof of the home and has clear exposure to all directions. For the year long study, we made a number of improvements to our model which estimates sky conditions from solar radiation. First, we and others noticed that the UW equipment in Seattle was uniformly recording lower radiation than the two other stations, even on completely clear, sunny days. So we normalized the radiation on the Y axis such that that all stations were recording nearly identical radiation on clear sunny days.
This reduced, but in no way eliminated, the advantage rain shadow locations had over Seattle. Next, we made our seasonality model much more sophisticated. Originally, we used radiation and "bright sunny hours" thresholds computed on a monthly basis to estimate sunny days. The problem is those thresholds are very different at the beginning of a month like February than at the end.
So we moved to a daily threshold for these values, which is much more accurate. This change made the model more accurate, but did not change overall comparative results dramatically. Finally we compared our model's results for Seattle to the National Weather Service evaluations of average daily sky conditions to check for consistency.
The weather service categorizes days as on average as, "Cloudy", "Partly Cloudy", or "Clear", based on automated hourly observations. We found that our totals for cloudy, and the sum of partly and mostly sunny days, lined up quite well with their observations; however, our category of "mostly sunny" is a little broader than their category of "Clear". Overall though, the consistency was encouraging. Of course the weather service only does sky condition summaries for a small number of cities, none in locations such as Sequim, Port Townsend, or Anacortes, so that is why we went with the radiation approach.
Study data was aggregated, analyzed, and graphed using Microsoft Excel. Olympic Rain Shadow, Oct September This report is a comparison and analysis of the sunshine in downtown Seattle, Washington vs. Spring Feb-May saw the highest number of rain shadow days per month, at nearly 8!
Summer Jul-Sep saw rain shadow areas and Seattle with nearly equal mostly sunny days. Report Detail: Our data shows that the climate in the rain shadow was clearly brighter and sunnier than downtown Seattle, with mostly sunny days vs. Report Conclusion The Olympic rain shadow has a dramatic impact in the amount of incident light and number of sunny days recorded in locations like Sequim when compared to downtown Seattle.
Appendix: Monthly Totals We also have archived monthly rain shadow climate summaries and individual monthly reports with daily sunshine charts and radiation plots. Precipitation July High Low Annual Rainfall US Avg: Annual Snowfall US Avg: 25". Precipitation Days US Avg: Sunny Days US Avg: Select Map Options. Reviews for Seattle Reviews. Great and beautiful place to live, but expensive. I spent 57 years there before moving to the other side of the country.
There is no income tax. It is surrounded by nature, including mountains and Read More. Agree 78 Disagree Bob Reply 1 Reply.
Why flash floods are so dangerous. Why snow and blackouts in Texas are a preview for all of us. What is the 'Ring of Fire'? How to prepare for severe weather.
What 'rapid intensification' means for storms. The future of climate change is here, scientist warns. Steer like this to stay out of accidents in the snow. You can thank pop culture's depiction of the city in films such as " Sleepless in Seattle " and shows like " Grey's Anatomy.
In some ways, it's an image that's understanable, especially when you consider that Seattle can experience more than cloudy days per year. But most of those days are just that -- cloudy and not rainy. The annual average rainfall just shy of 40 inches per year. Not even enough to crown the Emerald City in the top 30 of America's rainiest. The likes of Boston, New York, Atlanta and Miami all trump Seattle in annual average rainfall, in some cases by a wide margin.
However, Seattleites have endured a rather unique streak of both gloomy and soggy weather over the past two months.
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