Big Waves Hit the Northwest Coast from an Immense Storm Offshore

The Washington Coast is being pummeled by unusually big waves, some as high as 30-40 feet!  For example, buoy 41, right off the central WA coast observed a significant wave height of over 30 ft (see plot and map below)

Buoy 50, right off of Newport, Oregon, got to 35 feet this morning.

And a Westport surf cam shows an angry sea.

My colleagues at the National Weather Service currently have coastal flood and high surf warnings up for the Washington and Oregon coasts.

 The National Weather Service runs a wave prediction model, called WaveWatch III, the predicts wave heights (using weather prediction models to drive the wave model).  The WW3 forecast of significant wave height for 1 AM last night predicted a slug of very high waves of 13-14 meter height (43-46 ft) approaching our coast. 

No wonder my friends at the National Weather Service had warnings out!

Here is a blow up of the predicted waves at the same time.

Why such big waves?  Because there is a HUGE, intense, and slow moving storm (midlatitude cyclone) over the northeast Pacific. 

I mean a stunningly big storm.  Here is an infrared satellite image last night...you can see the immense swirl of clouds circling the system.

The sea level pressure analysis at 4 PM Wednesday shows the extraordinary system, with a central pressure of 964 hPa....very deep for a low that far south. 

You notice the extreme pressure gradients around the storm, particular on the south and west sides?  Those are associated with very strong winds.
In fact, the surface wind forecast from the UW WRF model for 7 PM Wednesday, indicates SUSTAINED winds of 50 knots around the south side of the storm.

Wind waves depend on the strength of the winds, the distance the winds are blowing over the water (the fetch), and the length of time the winds work on the water.

With a huge, intense, slow-moving storm like this, all of these elements are maximized to produce big waves offshore, which propagate away from the storm (and towards us) as swell.

Be very careful if you go wave-watching on the coast.  Sneaker waves can come in and inundate previously dry locations. 

And I hope that no cruise ships are in the area....😉.  In fact, the latest real-time ship tracker image shows virtually no ship traffic in the region of strong winds and big waves...

from Cliff Mass Weather and Climate Blog http://ift.tt/2Dgr8Dw