Understanding Sea Condition Forecasts

[CamB25]

I need some help from old salts. I trying to translate a sea condition forecast into something simple - is it great, OK, or terrible offshore. I'm confused about how to interpret swell versus wave height, direction, period and winds. Here's the site I use:

https://www.tide-forecast.com/locations ... sts/latest

As an example, today's forecast for 11am is:

Swell 3 ft from the SSE
Wave height 3
Period 5
Wind 20 mph from the SW

How do I use this data to determine if today is a good day to head out?

Thanks!
Cam

[ktm_2000]

the 5 second period would have me questioning.....

wave height isn't a big deal, period is, long duration is your friend

[ktm_2000]

to follow on

https://marine.weather.gov/MapClick.php ... nKC4yjMKUk

NOAA says building wind today

SW winds 10 to 15 kt, increasing to 15 to 20 kt in the afternoon. Isolated gusts up to 25 kt late. Seas 3 to 4 ft. A slight chance of showers and tstms in the afternoon.

I use windy.com and look for if the winds are building or dying down
https://www.windy.com/?34.411,-74.773,7

[Joseph Fikentscher]

I also use the Windy app on my iPhone.

[1962 31]

fish weather is a great app
try and stay away from square 5ft at 5 seconds sucks 5 at 12 no biggie

[Tony Meola]

Cam

I have to agree with the above. Period between waves is what it is about. 5 seconds is getting tight which is going to be bumpy. As an example a 6 foot sea with a 12 second period would be sleigh ride for a small boat. Up one side of the mountain and down the next without slamming.

Fish Weather and Windy are actually the same outfit. They are owned by Weather Flow who builds the Tempest Weather station.

If anyone is interested in a great simple weather station, with no moving parts, Tempest is the way to go. I purchased one last year. They have an interesting concept in regard to predicting the weather and actually it is pretty accurate.

I purchased it to see what I was up against before I even think about going out. What is pretty unique is that anyone can download their app. and access the Tempest weather map which shows every Tempest unit around the world. You just need to pick find one on the beach near you and you can see wind speed and direction in real time.

If you have a Tempest unit, it even registers lighting within 25 miles of its location.

[CamB25]

Thanks! I'm always looking for a closed-form solution, but experience tells me nature is not that simple.

I like the windy app. It seems in agreement with my app regarding wind direction and speed. I'm sure they are all getting the raw data from the same source.

"stay away from square" I might be able to remember that!

Today would be a good day? low (0 to 10mph)winds not aligned with swell direction
8a - 3ft at 7sec
11a - 3 at 6
2p - 2 at 6
5p - 2 at 6

Friday early good, late not so good? 20mph winds aligning later with swell direction
5a - 3 at 7
8a - 2 at 6
11a - 3 at 6
2p - 3 at 4
5p - 4 at 5
8p - 5 at 5

I need to start keeping a logbook with forecast and ass-o-meter data.

[ktm_2000]

Cam your idea of the logbook is a good one, figure out what conditions you can run in and be comfortable and look for those days.

To me it is all about the wind / direction, I look to go out when the wind is steady or dying down. Pick your poison too, While it is not ideal running out into a head-sea is a lot better than running home in a head-sea. There have been quite a few times I've headed east and got 35 miles offshore and started surfing down waves which the Bertram excels at, the oh $hit is realizing in order to get home I've got to head back into it.

[CamB25]

Matt - that's the typical pattern around here. Winds increase and shift to blow from the SW during summer afternoons. Great when you head out, rough when trying to get home. It's been generally windy here for a month or more. I might poke out tomorrow morning early for a joy ride and log the first entry in my trip book.

[Carl]

Wind creates waves
More wind makes more waves
The longer it blows the more bigger the waves
The more distance the wind has on the water (fetch) the more the waves have a chance to build.

With waves, once the wind dies down so do the waves.
The waves come from the same direction as wind so you can plan your trip accordingly.
Offshore winds, inlets, river s with incoming tides are a different story

Going out when its windy can be okay if the winds blowing off the shore and your close to the shore as the wind does not have a chance to build up the waves. Move away from shore or wind picks up is another story.


Swells are waves created by wind too...but from far away, think offshore storms. A swell does not build or subside with local weather conditions. Sort of...as a swell and a wave can kinda combine.


Period, the time in seconds for a wave to pass by crest to crest or trough to trough. A long period is a gradual rise and fall, think rolling hills. A short wave/swell period is like going offroad.

I tend to think of the wave or swell height and count to myself the boat going up and down in that period of time...5' in five seconds that boat is coming down and heading back up going slow, going fast all bets are off.


Then comes a swell and wave action together, they can combine and or make confused seas depending on which way they are going. That on top of local issues as inlets, tides, rivers etc.


A logbook is a good way to realize what happens under certain conditions and soon you kinda know what to expect when you hear a forecast.

my .02 layman interpretation of how I sorta understand it.

[Ironworker]

What I've learned in 50 years of offshore fishing and 40 years of flying is any forecast that is more than 24 hours old is not accurate. I like 24 hours for fishing and 8 hours for flying. I still check both immediately before I launch. BTW, forecast are OK but for real-time conditions, I like to check the buoy reports where I'm planning on fishing. In the OP you didn't say if you're running far offshore or fishing nearshore. Its makes a big difference to me.

Generally these days in my 26' CC anything over 3 to 4', I'm looking for something else to do. I really like 2 to 3s with a 6 sec or more period but its not often you get that forecast.

Also if the wind is blowing against the current all bets are off. Check the NOAA buoy reports.

[Amberjack]

I’m pretty much with Rick on this and probably even more analog. To go anywhere interesting from Seattle you need to cross the Straits of Juan de Fuca. When I first started venturing out one of the more experienced mariners on the dock told me to understand “sooner or later the Straits will kick your ass”. I learned from experience it’s not just wind speed, wave period, etc. up here it’s a lot of localized stuff, mostly to do with chaotic bottom contours, strong tidal flows and the Olympic Mountains making for unpredictable weather. Too much to chart or graph or for me to always be aware of. I had my fanny handed to me a couple times, now I’m a lot more cautious.

[CamB25]

Checked the forecast this morning and...it's changed a bit from yesterday:

Topsail Inlet

8am:
swell 2.5 SE
3 ft height
6 sec period, decreasing to 4 by 2p
winds are 10mph from south increasing to 20, SSW
low tide is 0712

I'm going to check it out.

[Carl]

Also if the wind is blowing against the current all bets are off. Check the NOAA buoy reports.

Very true.... I've gone out when the "current conditions" didn't quite meet reality. It's so much nicer today when you can get real-time info at your fingertips.

[Marshall Mahoney]

I find that every time I plan a trip based on a forecast of, for example 2 to 3 foot seas, I end of adding them (2+3) once I commit and am 30 miles off shore battling 5 footers...
Also, 20% chance of rain means you will be getting rained on at least 20% of the day.

[CamB25]

Well, in terms of the change in conditions, the forecast was spot on. About 11:30am wind speed doubled, turned, and seas responded. Started out OK. 3 foot prediction seemed correct, light winds, but the sea was confused...not rolling in from one direction, but 2 directions. no white caps. it was fine trolling a mile or so off the beach. Short runs at 25 mph were just OK. Anchoring would have been rougher, obviously.

We went out Topsail inlet which is relatively shallow, shoaled, unmanaged. Stacked up pretty good there. Would have been slamming in any other boat I think. Set out the rigs, turned south and did a slow troll all the way to Masonboro inlet. Nearing the inlet, pointing into the wind, waves were splashing over the bow. Much steeper waves and a little bigger than early in the day. white caps. Went in the inlet (managed, deep water) and ran the ICW all the way home with the wind at our stern. Rides like a Cadillac with just a touch of tabs.

All in all great fun. Roughly 50 mile round trip. Learned alot, and caught one small spanish. Back at the dock by 12:30. Really blowing by then. Would not have gone out based on what we experienced today.

Score from 1 to 10, with 1 being small craft advisory and 10 being flat calm, I'll log in a strong 6, degrading to 5 late.

[Joseph Fikentscher]

Sounds like a fun day. Remember, the Bertram will take more abuse than you can, but safety is the key. And I am sure yours was the prettiest boat out there.

Im missing the spring fishing season down here in Southport. Just had bypass surgery about a week and a half ago. Dr won't clear me for three months.Spanish, Kings, Mahi are all showing up. More as you travel offshore.

What was your fuel usage for the 50 miles?

[Carl]

Just had bypass surgery about a week and a half ago. Dr won't clear me for three months.Spanish, Kings, Mahi are all showing up. More as you travel offshore.

As you are here, it sounds like you are alright, glad to hear that!

Listen to Dr's orders and you'll have many more seasons to fish...this year, bluegills n crappies and leave the big fish to eat. It's all good, get right and move on forward.

[Joseph Fikentscher]

Thanks Carl, The first couple of days in ICU were tough, but after that Im feeling better every day. Lots of walking. Should have a full Dr's release by August with no restrictions. Looks like I'll make the fall run of kings and grouper.

[Carl]

... Should have a full Dr's release by August with no restrictions. Looks like I'll make the fall run of kings and grouper.

If you do, all well and good, IF not just be happy to be here.

[Amberjack]

They could have asked me for advice…..

https://www.kiro7.com/news/local/race-a ... CSRTCAGJA/

When I first started venturing out one of the more experienced mariners on the dock told me to understand “sooner or later the Straits will kick your ass”. I had my fanny handed to me a couple times, now I’m a lot more cautious.