Surf Forecasting

[meaks_85]

ok
so
im very new to this
and
the lows produce the swell right?
and the lower the L the larger the swell
e.g most lows are around 1020
so.. whats the best guide for knowing how big it will be at ur local?

A very breif rundown for you,
yes lows do produce swell, not always the case that the lower the low the larger the swell.
WIND is what makes the swell, Low pressure systems are responsible for this. The Law of thermodynamics is that air will move from a region of high pressure to a region of low pressure, Ie air rushes out of a region to fill the space left by a low pressure system hence why low pressure systems are accompanies by winds, A good way to remember this is next time you Fart understand that the pressure inside your bowels exceeded the pressure outside your sphincter therefore air rushed out in an attempt to re balance the pressure inside and outside . same thing happens outside, sun heats up air- hot air is less dense therefore it rises- cooler air then rushes to fills in the space left by the rising warm air.

When you look at a weather map you will see all these funky lines, they are called isobars and represent the atmospheric pressure, generally the closer the bars are together the lower the pressure and more wind there will be. Air rmoves clockwise around a low pressure system and anticlockwise around a high pressure system. So when you look at the map follow the isobars around and you will be able to tell a number of things
the most important are
1) whether the wind will be offshore at you beach
2) wheether there has been a low pressure system off the coast that may have produced the swell.

check out the ocean if you see a low pressure system in your areas swell window then follow the isobars around and see if there is an extended rregion of strong winds blowing towards you beach. the size of the swell will be determined by a number of things
1)the wind strength
2)the wind direction
4)the duration of the weather event-how long are the winds blowing for
3)the fetch, or the size of the area that has these winds blowing over. ie a tight low pressure system may have strong winds blowing east over a short fetch which may possibly lead to a swell the same size as a low pressure sysstem that had lighter winds but blew for longer or over a longer distance.

So the best guide is to keep an eye on the charts and see how low the low is, how large the fetch is and how long the sytem will last. couple that with what local winds are doing at your beach and you will have an idea of what condidtions will be like. Depending on where you live these the ease of exactly predicting swell size is very differrent. for example where i live in south oz we get swells that are produced from weather systems SW of western australia so these swells take a long time to get to the Adelaide coast, along the way they degrade in size or can even be blown flat by opposing winds from weather systems closer to the coast. QLD seems to get much shorter range swells that are produced fairly close to the coasts and take less time to reach the coast and lose less size.

thats where swell models come into play, unless youve been watching the weather charts for a very long time and know the ins and outs of these weather systems your better off looking at swell models such as surfline or http://www.lajollasurf.org/gblpac.html, which will predict the swell for you. However knowing the above details i set out for you and using bouy data you can then double check the swell models closer to the expected arrival date and make sure the swell is around and the winds are favourable for your chosen destination.

hope this helps, happy forcasting

yeah, nice and brief!!! haha

[doclach]

Josh_boogs asked why we get the 'summer flats' here. Basically it is because the Polar fronts mve towards the equator in winter, giving us more wave generating activity in our southern swell windows.
I'll put some reading links in on the great circl lines and stuff that defines out swell windows in Oz:

Some good stuff on wave basics:
http://www.stormsurf.com/page2/tutorial ... sics.shtml

Some good diagrams on our swell windows:
http://www.coastalwatch.com/news/articl ... icleId=177

[doclach]

A damn fine article on the current big swell event which has led to the Eddie being run and how it compares to big swells of the past:

http://www.surfline.com/surf-news/how-d ... t_39231/1/

[Matt P]

Hey guys some very good reads in here.
Also, I have noticed that there is usually a bit of swell around the full moon. I am not sure whether this is due big changes or whatever but I have just noticed it (not sure if this has written here before - I kind of skim read it)
I was also wondering if anyone had a buoyweather premium account that they wouldn't mind sharing

[Conjob v1.1]

Bouyweather uses the exact same raw buoy data as seabreeze but charges suckers for it while seabreeze gives you 7 days for free.

[Matt P]

Thanks

[Conjob v1.1]

Here is a direct quote.

Quick one: for those who say Windguru (or whatever) is better than other forecasting sites. You should be aware that Windguru, Seabreeze, Magic Seaweed, Buoyweather and a few others are all EXACTLY THE SAME. They just use a direct feed from Wave Watch 3 data, and there is no human element whatsoever. The only difference lies in where they put their GPS point in the ocean.

[meaksy]

Also, I have noticed that there is usually a bit of swell around the full moon.

Hey Matt, the position of the moon and sun can play a large part in the waves because they control the tides (the moon more than the sun in most locations)
have a read of the first part here it should help you understand the basics of tides and how they may effect swell.
http://home.hiwaay.net/~krcool/Astro/moon/moontides/

If ya cant be bothered going to the link here is the part you'll find most interesting

The word "tides" is a generic term used to define the alternating rise and fall in sea level with respect to the land, produced by the gravitational attraction of the moon and the sun. To a much smaller extent, tides also occur in large lakes, the atmosphere, and within the solid crust of the earth, acted upon by these same gravitational forces of the moon and sun.
What are Lunar Tides
Tides are created because the Earth and the moon are attracted to each other, just like magnets are attracted to each other. The moon tries to pull at anything on the Earth to bring it closer. But, the Earth is able to hold onto everything except the water. Since the water is always moving, the Earth cannot hold onto it, and the moon is able to pull at it. Each day, there are two high tides and two low tides. The ocean is constantly moving from high tide to low tide, and then back to high tide. There is about 12 hours and 25 minutes between the two high tides.

Tides are the periodic rise and falling of large bodies of water. Winds and currents move the surface water causing waves. The gravitational attraction of the moon causes the oceans to bulge out in the direction of the moon. Another bulge occurs on the opposite side, since the Earth is also being pulled toward the moon (and away from the water on the far side). Ocean levels fluctuate daily as the sun, moon and earth interact. As the moon travels around the earth and as they, together, travel around the sun, the combined gravitational forces cause the world's oceans to rise and fall. Since the earth is rotating while this is happening, two tides occur each day.
What are the different types of Tides
When the sun and moon are aligned, there are exceptionally strong gravitational forces, causing very high and very low tides which are called spring tides, though they have nothing to do with the season. When the sun and moon are not aligned, the gravitational forces cancel each other out, and the tides are not as dramatically high and low. These are called neap tides.
Spring Tides
When the moon is full or new, the gravitational pull of the moon and sun are combined. At these times, the high tides are very high and the low tides are very low. This is known as a spring high tide. Spring tides are especially strong tides (they do not have anything to do with the season Spring). They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon.

Neap Tides
During the moon's quarter phases the sun and moon work at right angles, causing the bulges to cancel each other. The result is a smaller difference between high and low tides and is known as a neap tide. Neap tides are especially weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another (with respect to the Earth). Neap tides occur during quarter moons.

[aboard2]

QUESTION
I have never really under the onshore offshore winds but i dunno a deffinition would be quite swarve

thanks:)

[kc_bodyboard]

Onshore is when the wind is blowing towards the land(onto the shore ie onshore) usually in the afternoon when the wind goes inland for the night, the makes the waves break closer to the shore and generally shit. eg in east coast easterlies are onshore, perth westerlies are onshore

Offshore is when the wind is blowing away for the shore and smoothing the wvae face and making better riding conditions most common in the morning when the wind comes back from inland back out to sea.
eg. in east coast westerlies are the shit, on west coast Easerlies are the shit.

[aboard2]

Thanks for that kc

[captain_awesome]

Here is a direct quote.

Quick one: for those who say Windguru (or whatever) is better than other forecasting sites. You should be aware that Windguru, Seabreeze, Magic Seaweed, Buoyweather and a few others are all EXACTLY THE SAME. They just use a direct feed from Wave Watch 3 data, and there is no human element whatsoever. The only difference lies in where they put their GPS point in the ocean.

there the same info but they layout is also a big factor, for me i like magic seaweed as it has it all on a picture, and if i feel like genius i use seabreeze, but hate all the other ones

[caspian]

virtual bouys NOAA or whatever it's called does it for me. Really it's all pretty simple to understand.

the main thing is don't use the human forecast in coastalwatch and you'll be ok.

A question for WA-ers: has there ever been any swells with a direction further north of wsw? What would it take to cause these conditions? I keep on expecting a tropical cyclone to one day swing southwest and give us some swell with a NW direction, but it's never happened.

[despes25]

i remember a while ago that there was that cyclone in bunbury and i surfed castle rock on that due to the swell basically being westerly direction or something and people said it was the best castle rock in quite a few years

[meaksy]

A question for WA-ers: has there ever been any swells with a direction further north of wsw? What would it take to cause these conditions? I keep on expecting a tropical cyclone to one day swing southwest and give us some swell with a NW direction, but it's never happened.

is a good question , it would be super rare considering the overall global air circulation. Most swells that SA and WA get come from the westerlies around the roaring 40s, air higher than the 30's tend to flow from east to west away from WA, you would needto get a large low pressure system or cyclone in the middle of the indian ocean but from my understanding, mid latitude cyclones are very rare. Could be wrong on some of that stuff but i think its close enough.
check this website, might find something usefull here
http://www.physicalgeography.net/fundamentals/7p.html