Tag Archives: tides

King Tides don’t always follow the tide tables

UPDATE: Dec. 19

An app used for reporting King Tides can also be used to report marine debris along the shoreline. Check out the news release issued today by the Washington Department of Natural Resources.
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Higher-than-predicted marine waters, brought about in part by recent weather conditions, have given us unexpected “King Tides” in many areas of Puget Sound.

I noticed that the waters of Hood Canal seemed exceedingly high this afternoon, as I drove along Seabeck Highway where the road hugs the shoreline. The waters were not supposed to be this high, according to tide tables developed by the National Oceanic and Atmospheric Administration, so I checked some actual levels recorded at nearby locations.

High-water levels measured on the waterfronts in Seattle, Tacoma and Port Townsend were nearly 1½ feet higher than what had been predicted by NOAA for those areas. For example, in Seattle the preliminary high-water level was listed at a tidal elevation of 12.98 feet at 12:54 p.m. today, compared to a predicted high tide of 11.56 feet.

This is the season for King Tides, a name given to the highest tides of the year. High tides, mostly generated by the alignment of the sun and the moon, are predicted for Christmas Eve, rising higher to the day after Christmas and then declining. But, as we’ve seen this week, as well as on Thanksgiving Day, predicted high tides can be dramatically boosted by heavy rains, low atmospheric pressure and onshore winds.

As one can see by looking at observed and predicted tidal levels in Seattle, the actual tidal level has exceeded the predicted level more often than not over the past 30 days — and lately it has been higher by quite a lot (shown in chart at bottom of this page). Actual levels are measured in real time in only 14 places in Washington state. One can access the charts from NOAA’s Water Levels — Stations Selections page.

King Tides are promoted as an event by Washington Sea Grant and the Washington Department of Ecology, because today’s extreme tides provide a reference point for sea-level rise caused by climate change. The highest tides of today will be seen more often in the future, and even higher tides are coming. Check out the blog post on Water Ways from Jan. 3 of this year. See also the website “Washington King Tides Program.”

Washington Sea Grant has posted a list of dates when high tides are expected in various areas, called King Tides Calendar. Sharing photos of high tides hitting the shoreline is part of the adventure, so sign up for MyCoast to share your pictures or view images posted by others, or download the cellphone app to make the connection even easier.

The chart shows the actual tidal water levels in Seattle (red) compared to the predicted levels (blue). Click to go to NOAA’s website.
Chart: NOAA

Be alert for tidal flooding and King Tide photos

Some of the highest tides of the year, combined with a strong low-pressure system, could provide “King Tide” observers with ideal conditions tomorrow (Monday) for taking pictures of near-flood conditions or even flooding in some places.

This is the third year the Washington Department of Ecology has put out a call for photos of high-tide conditions.

Photo of Poulsbo waterfront taken during “King Tides” Dec. 28, 2011.
Photo by James Groh, Poulsbo

“Documenting how very high tides affect the natural environment and our coastal infrastructure will help us visualize what sea level rise might look like in the future,” states Ecology’s “Climate Change” blog.

The King Tide photo initiative began in Australia in January 2009. Washington and British Columbia joined in 2010, followed by Oregon and California in 2011.

Tide tables predict that tides in Bremerton and Port Orchard will reach 13.4 feet at 8:28 a.m. tomorrow. Check on other locations and other days in Washington state at Saltwater Tides.

The National Weather Service has issued a coastal flood advisory for Western Washington because of low-pressure conditions, which could add 1.5 feet to the tide table prediction. That would put the Bremerton area at 14.9 feet. Check out the Weather Service advisory and the Kitsap Sun story.

While it looks like we’ll have a very high tide, it probably won’t be a record. I was unable to find historical data for Bremerton, but the record high tide for Seattle is 22.4 feet on Jan. 27, 1983. The tide tables predict that Seattle will reach 12.5 feet tomorrow, or 14 feet with the added 1.5 feet because of the low pressure.

Historical data can be found on NOAA’s “Tides and Currents” webpage after selecting a station.

Shortly after I posted this, Jeff Adams of Washington Sea Grant sent me an email to point out that NOAA’s numbers need to be corrected by subtracting 7.94, because NOAA uses a different baseline than we commonly use in this area. That would place the record in Seattle at 14.5 feet, much closer to what we may see tomorrow. I should have known that something was amiss with that data. For more on this point, check out Jeff’s blog, Sea Life. 

King Tides will continue through this week, declining slightly each day, then will return on Jan. 14.

I’m certainly not hoping for high water levels, but where they occur it would be great to have some photos. Feel free to send them to me at cdunagan, as well as uploading to the Flickr page called “Washington King Tide Photo Initiative.”