>High Tides Coming – 1-21-11


Illahee Shoreline.  Illahee has over 3 miles of marine shoreline that run from north of the Cheney Estates to University Point, and most of Illahee slopes toward Puget Sound with some breathtaking views of the water.  Those water views change some with the tidal extremes, and we will be be seeing some of them this weekend (1/22/11 and 1/23/11).

Highest Tides of the Year.  This weekend we will experience the highest calculated tides of 2011.  Using the Tide Chart put out by the shipyard for Bremerton, Sinclair Inlet, and Port Orchard, the Saturday tide will be 13.8 at 7:01 am, and on Sunday it will be 13.8 at 7:34 am.  Note that depending on winds, atmospheric pressure, and rain, the predicted tides can vary by as much as 1 foot either way.

The Variables.  The effects of the above variables of winds, pressure and rain are as follows:  High pressure systems decrease the predicted tides, whereas low pressure systems increase them.  A westerly wind in the Strait of Juan De Fuca is reported to increase tides as are heavy rains.  So if the variables all line up for increasing the tide, we could theoretically experience a 14.8 foot tide (see the second to the last entry for how Olympia can be affected).

NOAA Tide Datums. We found the attached NOAA chart helpful in explain the different tidal headings and their readings.  The readings are slightly different for Bremerton where the MHHW is 11.7 ft, and the MSL is 6.9 ft.
figure III-6
Figure III-6.  Tidal datums for the Seattle Station (Source: NOAA 2001)

Why Tidal Heights Change.  We found the following explanation about why there are such great 
differences in the Puget Sound tides, and why Olympia is so highly impacted.  The link is:
Be Aware of Tides
The shape of the Sound affects the tide as it moves through channels and inlets. In the Straight of Juan De Fuca, a 7.2 foot tide at Cape Flattery will reach Port Townsend 3 hours and forty minutes later and increase in magnitude to 7.9 feet. The tide will reach south Puget Sound 1 hour later and increase to 13.5 feet by the time the tide reaches Olympia. Extreme high tides of 18 feet have been recorded in Olympia.

Photos Requested.  If we do experience extreme high tides, it would be nice to get some photos that we can pass on.

Jim Aho