Introduction to swell prediction
Posted: Wed Jun 06, 2007 7:45 pmI've recently been trying to learn to forecast surf and thought I'd share what I've found out and collate it all in one post. Note: this is from a UK bias.
Before I start on learning to forecast - many websites do this already:
http://www.magicseaweed.com
http://www.surfcore.co.uk
http://www.a1surf.com/
Disclaimer: Remember these websites use compuational algorithms to predict the swell. Like any automated service it can't take into account all the variables and can't compare to 'local knowledge'.
On to forecasting: There are essentially 2 parts:
- Identify storms that create swell.
- Work out when/if swell from storm will reach you.
Identifying storms: This can be done in two ways, satellite images or pressure charts.
On satellite images storms are big swirls of cloud. This website lists a number of northern european viewing satellites: http://en.allmetsat.com/images/europe.php
On pressure charts storms are tightly packed isobars, that will form around a central point. Real time pressure charts are available here:
http://www.metoffice.gov.uk/weather/eur ... ssure.html
The storms are best if they are far off shore. The wind creates messy waves but given time these organise themselves into clean sets. The storms should be at least 500 miles away, ideally 1000+.
Will it get here: Winds really only generate swell in the direction they are blowing so this needs to be toward the break you are interested in. If it's not quite in the right direction then you still get part of the swell.
As for when - swell travels at different speeds (link) but around 500 miles a day is a reasonable rule of thumb.
That's it. A basic introduction to swell prediction.
To predict surf you need to also know the details of the break (best got through experience) and the winds.
The above only covers real time prediction. However the same techniques apply when looking at predicted weather charts. Some I use:
http://www.metoffice.gov.uk/weather/eur ... ssure.html
http://www.ecmwf.int/products/forecasts ... uv850_z500
http://www.euroweather.net/english/maps
Wave Buoys: These are floating weather stations in the sea. A map of buoys is here: http://www.ndbc.noaa.gov/maps/United_Kingdom.shtml
A close shore buoy tell you the conditions now/in very near future. A more offshore buoy essentially tells you what will be happening depending how far away it is (it's also harder to interpret the data).
Most of the buoy data is relatively straight forward. Wave height and period are values you should be familiar with, however won't translate perfectly to the break conditions.
The best buoy data is spectral. This shows the frequency components and direction of the waves at the buoy. They are only available for some buoys. Look for a useful buoy for your break then search for the data on here: http://polar.ncep.noaa.gov/waves/latest_run/
Spectral graphs can be a bit bizarre at first. The further from the centre the higher the period (higher period is good). The position shows the direction the swell is going to.
As mentioned by Northswell, this means you can see good waves that might be hidden by other conditions.
More buoy data: CEFAS
Further Reading:This post is based on the much more in-depth tutorial at http://www.stormsurf.com/page2/tutorials/menu.html
Surf Science by Tony Butt , Paul Russell and Rick Grigg has been recommended by many people. Link to Amazon
What I currently do is look at the charts, make a prediction then check it with magicseaweed. When there is swell I pay attention to the conditions at the break. If you cannot get to the break often (it's far away) then try making predictions then comparing it to a local webcam/forecast (Remember a webcam image may have caught the break in-between sets).
If I missed anything or made any mistakes feel free to correct me.
Edited to include Northswells comments.
Edited to include buoy stuff.
Before I start on learning to forecast - many websites do this already:
http://www.magicseaweed.com
http://www.surfcore.co.uk
http://www.a1surf.com/
Disclaimer: Remember these websites use compuational algorithms to predict the swell. Like any automated service it can't take into account all the variables and can't compare to 'local knowledge'.
On to forecasting: There are essentially 2 parts:
- Identify storms that create swell.
- Work out when/if swell from storm will reach you.
Identifying storms: This can be done in two ways, satellite images or pressure charts.
On satellite images storms are big swirls of cloud. This website lists a number of northern european viewing satellites: http://en.allmetsat.com/images/europe.php
On pressure charts storms are tightly packed isobars, that will form around a central point. Real time pressure charts are available here:
http://www.metoffice.gov.uk/weather/eur ... ssure.html
The storms are best if they are far off shore. The wind creates messy waves but given time these organise themselves into clean sets. The storms should be at least 500 miles away, ideally 1000+.
Will it get here: Winds really only generate swell in the direction they are blowing so this needs to be toward the break you are interested in. If it's not quite in the right direction then you still get part of the swell.
As for when - swell travels at different speeds (link) but around 500 miles a day is a reasonable rule of thumb.
That's it. A basic introduction to swell prediction.
To predict surf you need to also know the details of the break (best got through experience) and the winds.
The above only covers real time prediction. However the same techniques apply when looking at predicted weather charts. Some I use:
http://www.metoffice.gov.uk/weather/eur ... ssure.html
http://www.ecmwf.int/products/forecasts ... uv850_z500
http://www.euroweather.net/english/maps
Wave Buoys: These are floating weather stations in the sea. A map of buoys is here: http://www.ndbc.noaa.gov/maps/United_Kingdom.shtml
A close shore buoy tell you the conditions now/in very near future. A more offshore buoy essentially tells you what will be happening depending how far away it is (it's also harder to interpret the data).
Most of the buoy data is relatively straight forward. Wave height and period are values you should be familiar with, however won't translate perfectly to the break conditions.
The best buoy data is spectral. This shows the frequency components and direction of the waves at the buoy. They are only available for some buoys. Look for a useful buoy for your break then search for the data on here: http://polar.ncep.noaa.gov/waves/latest_run/
Spectral graphs can be a bit bizarre at first. The further from the centre the higher the period (higher period is good). The position shows the direction the swell is going to.
As mentioned by Northswell, this means you can see good waves that might be hidden by other conditions.
More buoy data: CEFAS
Further Reading:This post is based on the much more in-depth tutorial at http://www.stormsurf.com/page2/tutorials/menu.html
Surf Science by Tony Butt , Paul Russell and Rick Grigg has been recommended by many people. Link to Amazon
What I currently do is look at the charts, make a prediction then check it with magicseaweed. When there is swell I pay attention to the conditions at the break. If you cannot get to the break often (it's far away) then try making predictions then comparing it to a local webcam/forecast (Remember a webcam image may have caught the break in-between sets).
If I missed anything or made any mistakes feel free to correct me.
Edited to include Northswells comments.
Edited to include buoy stuff.
) but the basics look great to me, I bought the surf science book to try and learn to predict surf and stuff but it was all a bit much for me - not exactly bedtime reading.
