Chesapeake Bay Wave Forecasting

[it4llc]

I've been using Windy for weather on the Bay. The wind forecasts seems to be relatively accurate. However, the wave forecast is 1' 95% of the time, occasionally 2', even on days when I've been taking water over the bow. Does anyone have recs for apps that are better for weather/wave forecasts in the Bay? I've started to do my own mental estimates based on the wind, but am curious what other people do...?

 

[KKRCRACE]

Gremlin,
Do you keep your boat on E dock at Harrington Harbor North? My C24 is on M dock. I’m pretty sure I walk past you often.
KKRCRACE

 

[it4llc]

Yep, that's us! We're in E5, and there's also a R29? in E1.

 

[rpmerrill]

Try Ventusky. I can't totally vouch for its accuracy, but it is pretty handy.

 

[knotflying]

I use sailflow and windy. My general boating experience is wind velocity and direction and I can figure out whether to go or not. My limit is usually 15 MPH on the beam, which will develop waves that are my limit. If they are coming from thebow they are tolerable. From the stern you have to practice throttle control. As far as Windy goes I look at intervals. Seconds between waves of double the wave height and more is what I prefer. Also keep in mind that what you experience in your boat always seems like the waves are much higher than forecast. Also wave heights are an average so what you see will be larger and smaller than predicted. Knowing how your local waters reaction to wind is something you will also develop over time. As an example, any wind coming from the north ( over land and pushing against the waves coming into shore) always make for fairly calm seas.

 

[it4llc]

Thanks - that's more or less what I've been doing. It seems like when the wind is from the south and in the double digits in the afternoon, the long fetch lets some decent waves build up in the Bay. Last weekend in what was supposed to be 1' waves according to Windy, we were tacking to keep from taking the waves straight on the beam - we had a couple rolls that spilled everything off the counter. And I get the 'waves seem bigger on the water' factor, but Windy has said 1' seas when it's been close to flat, and it's said 1' seas when when we've had water over the bow. I'd hate to be on the water when they forecast 3-4' waves. 🙂

 

[NorthernFocus]

As someone mentioned earlier wave period is as/more meaningful than wave height when it comes to how "rough" it is. Predicted wave heights reported by weather services are based on average wave height calculations which are actually pretty accurate. But in enclosed waters often times there isn't enough fetch for the seas to become "fully developed". Which means shorter/steeper often breaking seas. For example, with 10 kts of wind waves become fully developed in about two hours over a fetch of about 10 miles. But at 20 knots it takes 10 hours and about 85 miles of fetch for fully developed seas of about 5 feet with a period of about 6 seconds. But with inadequate time/fetch, waves build to un unsustainable height and break. So wind that comes up quickly and/or on enclosed waters causes shorter periods and steeper seas. Which most of us call "rougher" conditions. Anyone who has been through a rain squall has experienced this phenomenon. Then throw currents into the mix and things get even more interesting.

We boat on Prince William Sound which has very few places with adequate fetch for seas to develop fully with more than 15 knots of wind. Consequently it is typically much rougher than predicted wind/wave forecasts suggest. Unfortunately it takes time to develop one's own store of "local knowledge". 🙁

 

[it4llc]

Thanks Dan - that is interesting info. And to the points raised on the period, waves are often pretty tight in the Bay when they come up, 2-3 sec according to Windy (and my experience), so I try to look for a little gap in the bigger ones before tacking... It does take some time to digest and learn, but learning all of this is one of the fun parts of boating to me.