Understanding Puget Sound Weather

[FabioC]

The other puzzling observation related to weather in the Puget Sound is: why Windy or similar apps or Weather.com cannot forecast fog at all? Some days the fog is extremely thick throughout the bay, but the forecast remains on "sunny" (I understand that above the fog may be sunny, but what use is there in a forecast that neglects to observe fog?).
VHF weather seems to be able to predict fog (albeit not always reliably, but at least they try and often they are correct), why the others cannot?

[Stu Jackson]

Good advice from many. Don't rely on only one model. The Canadian weather forecasts for the Strait of Georgia (I know, it's NOT Puget Sound) covers a LOT of area, because the Strait is HUGE, and is not localized (that's my point).


I, too, use Windy, and find zooming in A LOT works just fine for local conditions.


I wrote this earlier this year for Mainsheet magazine, a publication for and by Catalina owners associations:


Sailing in SWBC


We bought our first boat in San Francisco in 1983, and this boat in 1998. I sailed it up to B.C. in 2016 when we moved to Vancouver Island.

The utter predictability of wind in SF Bay was a luxury I didn't really fully appreciate, although I certainly fully appreciated the ability to sail regularly, as in always. Even in winter, there were known regular weather patterns. Kimball Livingston's excellent book Sailing The Bay is superb in explaining things.

Now that we're entering our fourth sailing season, I have learned a few things that I didn't "need" to know back down in Northern California with its predictable daily wind cycles. There are definitely local areas here of consistent winds. Ganges Harbor all the way past the Pender Islands, Satellite Channel northwest of Cape Keppel at the southwestern end of Saltspring Island (called the Cowichan Doctor), and my home port of Maple Bay, all can be as regular as SF Bay. A mere mile away it can be dead calm.

I've learned that if you want to sail, you have to be ready to do so, quickly and pleasantly. On Monday August 17th, we had a really nice wind all the way from Maple Bay north through Stuart Channel to Thetis Island, almost unheard of without a major weather front moving through. We took advantage of it and had a memorable sail.

Otherwise, we have the proverbial "trawler with a stick."

But it sure is gorgeous. I don't miss the city lights at all, the stars at night are big and bright and it ain't even Texas.

A friend had a sistership that he bought new for as long as I've had my older model. Last year he sold it for a trawler, a Ranger 29. He recently wrote:

After an abortive effort to embrace power boating, we are looking forward to returning to the sailing world. The power boat, a Ranger Tug, works beautifully and is a delight to be on in anchorages and at the dock. But after one summer of cruising we found that we really missed sailing and the simple pleasure of working with the wind to get from one place to another.

So, it seems that it all depends on your perspective.

My first couple of seasons here were spent mostly motoring from place to place, with the deliberate intent to see as much as possible to learn what we liked and didn't, so as to be able to choose where we'd like to go back to. We found some "favorites" as well as some "never goin' back agains."

Now that we have a firmer grasp on distances, times and tides and currents, and local weather patterns, we can better plan our cruises to attempt, I say attempt, to maximize the time under sail.

But all in all, it's most important to me to simply be able to be on the boat.

Your boat, your choice.

Good luck, stay safe, be well, and enjoy being on the water.

[Cheechako]

Originally Posted by Cheechako

The only thing I have to add is that on the VHF weather, Puget Sound has two oft used predictions: 5-15 wind which often means not enough wind to sail, rather than 15.
10-20 wind which often means it will blow hard sometimes. Further south in the sound south of Seattle it's very often windless in the summer.

Winter on the water in PS is hard to predict, you can get hammered sometimes. 35 not uncommon. If it is a north wind it will be more settled, but cold.
If a rain front is coming in it can get very strong... to 70mph. Often from the S-SE-SW.

In the summer, the Straight of Juan De Fuca can blow hard from the West, building into the afternoon. This gets pretty lumpy especially further inland close to the San Juan Islands by maybe 3pm. Almost every day in the warm months. And even more when the tide is going out.

Oh... and one thing I forgot.... The Divergence Zone. In PS the weather often comes in the Straight and from the South/West, divided by the Olympic Mountains. The two winds hit head on somewhere in the Puget Sound. That is the Divergence Zone. I have been racing north in PS with a spinnaker up and suddenly in a matter of seconds be head to the wind and have to change to beating! Often you can actually see the water change up ahead and have time.

[sv_pelagia]

I've posted info regarding very high resolution forecasts for British Columbia using Environment Canada's VIZAWEB:

https://www.cruisersforum.com/forums....php?p=3307352

[Lodesman]

Originally Posted by Cheechako

Oh... and one thing I forgot.... The Divergence Zone. In PS the weather often comes in the Straight and from the South/West, divided by the Olympic Mountains. The two winds hit head on somewhere in the Puget Sound. That is the Divergence Zone. I have been racing north in PS with a spinnaker up and suddenly in a matter of seconds be head to the wind and have to change to beating! Often you can actually see the water change up ahead and have time.

I think you mean Convergence Zone.

[Lodesman]

Couple of resources: https://a.atmos.washington.edu/marka/pnw.html
https://www.wrh.noaa.gov/map/?obs=true&wfo=sew

[Uricanejack]

When the wind blows out of the sound it’s going to get worse and rain
When the wind blows into the sound it’s going to clear.
When there’s no wind.
Your going to get fog from Port Townsend to Marrow-stone point.
In august all the way to Tacoma.

[SV__Grace]

Originally Posted by Uricanejack

When the wind blows out of the sound it’s going to get worse and rain
When the wind blows into the sound it’s going to clear.

This sounds interesting but I don't understand it, can you elaborate and provide an example or two?

[Uricanejack]

Puget Sound, Haro Straight, Straight of Georgia, Jaun De Fuca.
The usual weather patterns are greatly affected by the land.
The most obvious effect is the funnelling of the wind.

The wind tends to blow up or down the sound. Or straight.

It’s a very simplistic general tendency.

Generally if a low pressure is approaching the wind will be in E then South then west. Then North.

When the wind goes from E to SE the front is approaching.
So cloud will start high thicken and then rain.

when the wind goes round to the west the front has usually passed, shortly after the heavies rain.
The sky will start to clear.

Due to the funnel effect of the land you often don’t get the gradual change in the wind as the low passes.

The wind is funnelled and flows out of the sound from the south east.
The low is approaching.
When the wind switches and gets funnelled into the sound it has gone round to the west
The low has passed and the weather will clear.

There are other conditions. A high over the coast will funnel out the inlets and the sound.
Some of the summer systems will not bring rain only higher clouds due to the rain shadow effect of the Olympic peninsula mountains or Vancouver Island.

Summer fog is common on the sound when there is no wind.
Particularly out of Port Townsend from ST in to Marrow Stone Pt.
There is an upwelling of cold water from deep.
Warm air cold water fog.
The water temp in the sound doesn’t change much over the year.
So in the summer you get warm air of the land over the cold water of the sound.
Then you get fog.
It will often burn of by late morning.

If there is wind there is much air movement, the air doesn’t get cooled by the water so the fog doesn’t form or lifts.

Fog tends to occur in good weather when there is a high over the coast and not a lot of air movement.

These are just general trends. On a specific day it may be different.

So a rough general guide which way is the wind blowing into the sound or out of the sound.
Up the straight down the straight.

The Columbia River valley has a marked funnel effect which is similar though the influence of where the high and the low is you really notice the outflow.

The wind which blows in or out the sound tends to be related to the system low or high approaching from the pacific

[Adelie]

The Seattle area is the most difficult metropolitan area in the US to forecast for because of the Olympic mountains.

Apps and predictive programs are geared for open water, possibly also for the plains areas with no major land features.

In 20-50yr predictions will be better as the programs start to account for topography.