Thursday, January 17, 2019

Modest Winds Tonight, Stronger Winds Tomorrow Night

After a period of warm, benign weather, storms are now moving towards our region.  Tonight a modest, elongated low center is moving northward up our coast, as illustrated by the sea level pressure map at 7 PM tonight (see below).

The winds surged this evening, as illustrated by the maximum gusts at Seattle's West Point, where wind revved up to around 35 knots (about 40 mph).



24 hour from now (7 PM Friday), a  much stronger low-pressure center will be due west of Vancouver Island.  The pressure analysis shows an intense pressure gradient (change of pressure with distance) over the offshore waters, which will bring big winds over the water.


The wind gust forecast for the same time are impressive, with 60 knot gusts south of the low (wind gusts at 10 PM Friday are shown).  Note winds are NOT strong in the center of the low.

Looking closer, as the storm approaches later Friday, winds will increase along the coast and over NW WA (see 6 PM gust forecast below)--as high as 50-60 mph in places.

Winds will increase later over central Puget Sound, strongest after midnight.

By 4 AM Saturday, the low has moved NW of Vancouver island, with a very large pressure change along the Vancouver Is. coast.


Wind gust are even stronger at that time, but shifted NW with the low.


Some big waves will be forced by the low, up to 9-10 meters high (see plot)
The winds here in Puget Sound will pick up again late tomorrow night as the second low moves by, but there is a lot of uncertainty, depending on exactly the path of the low.  Here is a plot of the UW many-forecast (ensemble) system.  Winds rev up after 10 PM Friday, but forecasts are all over the place.....will have to wait to have more certainty about the forecast.


3 comments:

MAC in Bellingham said...

Yes, I see the big difference (20 mph) between the NWS and UW in terms of maximum gusts. This morning, the NWS has reduced its High Wind Watch to a Wind Advisory. The UW and NWS forecasts track pretty closely until you get to crunch time.

MAC in Bellingham said...

Unless I am missing something, it looks like the UW models were way off in terms of intensity. NWS was quite a bit better, but NWS also terminated its north of Seattle wind advisory early with the 4 am update. This morning the Seattle NWS says:

"It's still going to be a breezy/windy morning with southerly winds gusting as high as 40 mph from Seattle northward."

I guess this could still happen, but there is not too much going on from any of the reporting stations at this time.

This storm had a lot of power (100 mph+ gusts on Solander Island on the northern part of Vancouver Island). It appears the center of the low headed towards the Queen Charlotte Islands.

MAC in Bellingham said...

Would still be very interested in why the UW forecast was so far off. NWS was off as well, but a lot better than UW.