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November 2016
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Record October Review

Posted: November 3rd, 2016
october-2016-ahps

Seattle with nearly 300% normal rainfall, the Cascades more like 200%.

October 2016 was the wettest October ever recorded in Seattle. 10.05 inches fell at Sea-Tac, which is 1.09 inches more than the previous record (2003) and 6.57 inches more than normal. Coincidentally, 6.57 inches is normal rainfall for November, so two months of rain fell in one.

 

It was only the tenth time that 10 or more inches fell in a month since record keeping began at Sea-Tac in 1945. (It was only the thirteenth time since the 1890s using other Seattle records).

 

There were 25 days with measurable precipitation (27 if you count “trace” readings). The previous October record was 23 days with measurable precipitation (1956, 1950, 1947).

 

There were 4 calendar days in October with an inch or more rainfall. Seattle averages 5 calendar days per year with an inch or more rainfall.

 

City-wide there were two statistically significant rainfall events: an atmospheric river October 13-15, and a frontal passage on October 26. Rainfall with the former was most noteworthy at long-durations. SPU’s Jefferson Park (North Beacon Hill) rain gage recorded 4.45 inches over a 72-hour period, which was good for a 10-year recurrence. The latter event achieved significance when its cold front stalled over the city and provided SPU’s Garfield Community Center rain gage with 0.46 inches in 30 minutes, also a 10-year return.

 

*Had originally posted that we were close to an annual rainfall record. At 35.05 inches since January 1st, we’ll end up above normal but probably not in a significant way.

 

JRH