WeatherWatcher: Regular weather returns, Forecast

Wednesday, September 20, 2017

Our regular weather has finally returned after an unusually long, hot and dry streak. We went from late July weather to early November weather in just over a 24 hour period. The sudden change was due to a change in the upper atmosphere circulation replacing our persistent ridge of high pressure with a low pressure trough out of the gulf of Alaska, a circulation pattern that is more typical during winter months. The pattern is going to change a little more in the next couple days to return the sunny weather but with temperatures much cooler than we've been used to.

Here are some graphs for September that show the dramatic changes. The daily average temperature graph is a good demonstration of the changes.

You can see how the first 5 days were exceptionally warm, and then a sharp drop off between the 7th and 9th down to near average, then the last few days it drops down much below the normal average.

Here's the daily high and low temperatures graphed out compared to average.

You can see how our highs and lows were above normal until the 7th, then the lows drop below normal, but daily highs were still peaking 5-9°F above normal until the 17th. The daily highs are getting shorter in duration (less than an hour instead of for several hours) due to the shorter days. This is why the daily average temperature in the first graph is a little lower than normal for the same time period despite the large difference in high temperature compared to normal.

Last but not least, our rainfall for the month: Shoreline didn't get much compared to areas north and south in the Puget Sound. The Olympic mountain rain shadow was affecting the area during the recent storm fronts that moved through. As a result we are still well below the normal for September. Most areas surrounding us, however, are closer to a half inch below normal.

Forecast: We are going back to a drying trend with clearing skies for the weekend and into early next week. High temperatures are going to stay below 70°F for the most part, generally in the mid-60's. Lows are starting to dip into the mid-lower 40's now so it is starting to feel much colder than we are used to. Some wet weather looks like it might return at the end of the month. I believe we are done with the smoky air and 80°F + temperatures for the year.

For current weather conditions please visit


Nanook September 21, 2017 at 11:58 AM  

Another nine months of winter and then it will be summer again. Spring and fall? No such thing in Seattle. It's either Summer (sunny) or winter (raining).

Post a Comment

We encourage the thoughtful sharing of information and ideas. We expect comments to be civil and respectful, with no personal attacks or offensive language. We reserve the right to delete any comment.
Facebook: Shoreline Area News
Twitter: @ShorelineArea
Daily Email edition (don't forget to respond to the email)

  © Blogger template The Professional Template II by 2009

Back to TOP