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January 2015

King Tides 2014-15, Take Two

Posted: January 21st, 2015


The second of three King Tide rounds arrives tomorrow morning. Predicted water levels will be at least a foot higher than average daily high tides (MHHW) each day through Monday. As always, or at least always has been, predicted water levels will be of only limited concern absent strong winds or low pressure, and the forecast looks pretty good.


Long term climate outlooks, though, do not look good. According to the latest research, seasonal and eventually daily tides will be of concern without storminess, and they’ll be of serious concern with. That’s why King Tides should be considered the leading edge of sea-level rise, or as The Seattle Weekly nicely put it, [King Tides show] what climate change has in store.


Middle-of-the-road projections for sea-level rise give Seattle 7 inches more coastal water by the year 2050, and two feet by 2100. Applying those figures, or the rates supporting them, to what we experience now, Saturday morning’s 13.21′ MLLW/10.86′ NAVD88 water level—the highest predicted tide of the year—will likely become an average monthly high tide by as soon as 2070, and an average daily tide by as soon as 2090. And this weekend’s 13.21’/10.86′ tide will be at 15.21’/12.86 by 2100. Without storminess.


Much in the way SPU monitors rainfall and landslides, we are watching King Tides closely. SPU manages myriad coastal infrastructure, and how we respond to King Tides and coastal flooding will ideally inform how we choose to adapt to long-term climate change.


NOAA Tides and Currents—Seattle
Washington State Department of Ecology King Tide Information
SPU Sea-Level Rise Information



The latest National Weather Service forecast for Seattle shows under an inch of periodic light rain falling tonight through Saturday. Sea-level pressure looks like it’ll be above winter normal through at least Saturday morning, and according to extended range models, through Monday’s final King Tide, as well. Southerly winds might pick up a little bit on Saturday morning, but if pressure remains high, coastal impacts will be low.


Over SPU’s mountain reservoirs, the latest forecasts have nudged rainfall amounts upward a bit to nearly 3″ tonight through Saturday. Snow levels still look to be too high for meaningful snow to fall.


NWS Area Forecast Discussion
NWS Forecast Table Interface—Seattle
NWS Forecast Table Interface—Tolt Reservoir
NWS Forecast Table Interface—Chester Morse Lake
SPU Water Supply Outlook