An predicted 11.6 high tide was enhanced significantly to look more like a 13ft tide by a strong low pressure system and associated storm.

This past week 2 or 3 low pressure centers merged in the eastern Gulf of Alaska to create an exceptionally strong low pressure system. Strong low pressure systems are typically associated with strong winds, big waves, and storm surge that leads to higher tides. Accordingly, Sitka was under a Wind Advisory from the National Weather Service that lasted from early Wednesday morning through Friday morning. Marine forecasts called for seas to 34 feet (which probably contributed to the surf in coastal Washington).

Coincidentally, the high tide predicted for Thursday afternoon was one of the higher ones of the year at 11.6 feet (for context, the very highest predicted tide of the year tends to be between 12.7 and 13 feet, depending on the year, and much of the year tides don’t get above 11 feet). Based on my subjective impression of the water height at Crescent Harbor (see photo above), I thought it was easily above 12 feet, and maybe pushing closer to 13 feet. Later, I was able to find the coastal water level monitoring data from NOAA and saw that the observed water level was nearly 13.4 ft, almost 1.4 feet above the predicted level.

The highest water level I remember seeing was during the 1984 Thanksgiving Day storm. I remember driving out the road with my parents and brother to look at the ocean near the time of the predicted high tide. Waves were pushing rocks up on the parking lot at Sandy Beach, Nelson Logging Road was well under water, and the waves were splashing up underneath the furthest-out trailer at Arrowhead Trailer Court (subsequently fill and a rip-rap wall was added to protect the trailers). On a subsequent hunting trip, I saw debris that had obviously been deposited by a high tide up in the woods several feet off the beach.

I was able to find historical information on the Sitka Station page of the NOAA Tides & Currents site. The predicted tide for that day was about 12.3 feet, but the maximum reported observation was nearly 14.6 feet. A higher predicted tide and greater storm associated increase made that tide much more significant than the one this past week which was unusually high, but not hugely so.