[Closed] Sea states in surf forecasts

It's the total distance between the trough and the peak.

1.3mtr is quite big to swim in, is it high tide down there ( here it's low ) if so wait until it goes out a bit before swimming.

That would be about chest high waves or so...

http://magicseaweed.com/help/surf-forecasting-basics/measuring-wave-heights

MSW says it's 2-3ft XOn at 5s, which means onshore unpleasant windy crumble dump..

windy crumble dump

It's the total distance between the trough and the peak.

At what point on the beach though? Waves get taller as they roll up the beach don't they?

Is it an explicit surf forecast or inshore waters ?

Surf.

It's all measured at the nearest buoy that the Met Office use. As the bouy bobs up and down, it measures the distance.
You couldn't realistically but a bouy for measurement 20mtrs off the beach due to the tides, it'd dry out at low water (in most places) and read zero of about 2hrs (or so) Some piers have measurement (pressure) on one of the stilts, like an oil rig would use (combined with Chanel bouys) then correlate the "up/down" movement.

Look at www.chimet.co.uk, here there is a pressure measuring gizmo that calculates the water pressure, gives a reading and smooths out the variables, it's a proven way of calculating waves.

Trinity House have loads of measurement bouys plotted around our shores, from them they produce not only current swell (which is where we all look, MSW and other weather related suppliers) but trends, and distribution of the water around our shores. Typically these bouys are in shipping lanes, or near, due to the need for deep draft vessels to manoeuvre around the UK (and elsewhere) The UK is highly regarded as No1 in this field.

For example E1 bouy in the Chanel off Plymouth sits with 8 tons of weight below it and 230mtr chain, this then allows the bouy to not "bob" but move with the swell. It's all recorded by Plymouth Uni and sent to Trinity House, there they produce the results.

Back to MSW, they produce a chart of all the bouys used for measurement around the UK. This is where nearly all the information to mariners is issued from in the U.K.

[url= http://magicseaweed.com/UK-Ireland-Wave-Buoys/1/ ]Wave bouy location chart[/url]

So for Bournemouth there is a mark off the Shingles Bank (near Milford on Sea/Hurst Point, this is a notoriously dangerous sandbank with very high tidal range) and another bouy just off Swanage.

What wave period? These 'surf' forecasts are just model predictions adn are typically for deeper water. THey may or may not have been transformed inshore depending on your source (I think MSW do try, windguru is just model output in deeper water). 1.3m could be massive somewhere like SW france with a 14s period or dribble at bournemouth with a 6s period.
Even the same wave height wave period combo can give markedly differnet real world results on differnet beaches.

THe issue you have with soemthing like windguru is that if the output comes from deeper water then you might expect wave hieghts to increase as depth shallows and waves shoal (up to brekapoint after which they decay), but actually reducing depth can increase dissaption due to 'friction' from the bed and so wave hiehfts actually reduce. Then you have wind direction etc.

I actually once thought about setting up a bespoke surf forecast service whereby I'd provide detailed and grounded personalised forecasts for people heading off to a certain area for the weekend/ weeks hols etc. but I decided it was probably a bit too niche at the time.

Well Chimet we use cost £450k to put in place, it has 5 measurement devices all over the Solent. It costs loads to maintain and is in the main funded privately.

It says Bournemouth Pier - it's this one I was looking at

http://www.surf-forecast.com/breaks/Bournemouth-Pier

Period of 5s means that they are small waves hence closer to the beach..?

Na 5s means the distance between the waves, the frequency. B'mth Pier must have a pressure monitor on it like Chimet, it's a popular surf location (and Boscombe pier)

You have to take the overall forecast given from the swell buoys, then get excited based on that forecast.. pop on down to the beach only to find is just South Coast crumble and swirling around like soup.

Occasionally, it all works. Then we all flock like lemmings because one of our mates has actually turned up to the beach in question and texted everyone on iM with the words "It's firing/going off, get down here....(insert beach)"

Thats not a bad site, it shows where the bouys it uses are located, then the local conditions based on the pier pressure sensor and the swell, tide state, wind etc...

Nothing better than going down and looking at the beach though..

I'm a far more relaxed person now I don't go chasing surf as much as I used to , living near bath does not help

Sorry not much help to the op

As others have suggested, dedicating what the waves are going to look like at a given beach from the buoy forecast takes years of experience/knowledge much of which is specific to the spot in question and based on relating what you actually see to what the buoys are saying.

The surf at a given spot depends on four main things

1- size of swell - bigger swell means bigger waves breaking further out from the beach, bigger currents and more power
2- wave period - the gap or time between waves passing you if you stood at a fixed point. The bigger the period, the more powerful and organised and generally bigger the waves will be at a given spot. Round here for example 1.3m @ 5 seconds would be waist high and very choppy, 1.3m @ 12 seconds would be overhead waves with well defined sets and lulls.
Longer periods tend to give more defined sets and lulls. A 5 second period will give lots of broken waves and generally be choppy. Doubt it would make for fun swimming conditions
3- wind strength and direction - offshore winds groom swells to give more organised and defined waves which are better to surf and easier to swim out past, onshore winds chop the swell up more making it worse to surf. For a given wind direction different spots will be affected more or less by the wind depending on the direction they face and their geography - a pier might give some shelter to cross shore winds. See here http://magicseaweed.com/news/onshore-vs-offshore/9050/
4- the spot itself. Steeper shelving beaches and reef breaks tend to have more powerful waves, gently shelving beaches have gentler waves. Beach breaks break off sandbars so the waves can break on lots of places, waves that break off shallow rock reef in areas surrounded by deeper water have more defined shape and are less affected by the wind.

It's complicated! Magic seaweed does attempt to give actual breaking wave face heights but it's often not that accurate. If you are looking at an "eyeball" surf report you need to know what scale the report uses (experience again I'm afraid!) Historically people used a "Hawaiian" scale which underestimates the size of the breaking waves face by about half - a 6 foot wave would be double overhead - to do with male bravado. A more genuine scale like surfline uses would call that same wave (where the wave face is twice an average man height) 10-12foot

Bournemouth must have a webcam that can actually show you what's happening at any given time.

Bournemouth must have a webcam that can actually show you what's happening at any given time.

Indeed

http://www.sortedsurfshop.co.uk/webcam_bournemouth

Hmm.. not too bad further out except at night I'd not want to be out far. The other night it was flat as a pancake and looked rally in icing, could've swum in a few feet of water by streetlight.

The pool was quite calm though 🙂 thanks for the explanation.

I like the idea of Chanel buoys.