Onshore vs Offshore

Ben Freeston

by on

Updated 1608d ago

Why does the local wind make such a difference to the surf? Why can we accurately track a swell from thousands of miles away and still have to stress about the wind playing ball on the day? We've modified our forecast to give you an even better 'at a glance' of the effects and you can test the new version now.

Simply select 'wind highlighting' above any forecast to turn on a simple traffic light guide to the best wind conditions, or click this link. You can turn it off at any time in the same way. Of course, as with our star rating and estimated surf heights, this is designed to make it quicker and easier to read your forecast. Local knowledge and digging deeper into the data is still key: that cliff that gives a little shelter from south west winds or the valley that funnels a cross-shore into an offshore at a nearby beach are the sort of things that experienced surfers will always benefit from working out for themselves, and we still give detailed wind strength and direction data to help you do that.

Green is good, red is bad. It's simple and it's no substitute for a personal interpretation, but our new 'traffic light' gives you a great chance to spot that little window of lighter winds at the end of the day.

Green is good, red is bad. It's simple and it's no substitute for a personal interpretation, but our new 'traffic light' gives you a great chance to spot that little window of lighter winds at the end of the day.

Offshore

Winds blowing from the coast out to sea are the gold standard for most surfers most of the time. The main function of these winds is to delay breaking. All things being equal waves will break in water about 1.3x their depth. But with an offshore wind this breaking is delayed. On a sloping beach that means the wave will break in shallower water and is more likely to pitch forward than spill. This means steeper faces and faster breaking waves, often creating better surf. It is possible to have too much of a good thing though: waves of marginal size with a very strong offshore may not break at all (before the shore) on a gently sloping beach and longer period swells will have an increased tendency to closeout in offshore conditions. These issues can mean that some locations behave better with no wind than an offshore wind on some swells.

Put an offshore wind against even a small swell and you have waves good enough to share. Notice that even on this average beach break in an average swell the upper third of the wave in the pocket is vertical, held up by that offshore wind.

Put an offshore wind against even a small swell and you have waves good enough to share. Notice that even on this average beach break in an average swell the upper third of the wave in the pocket is vertical, held up by that offshore wind.

© 2020 - Matt Coleman

Onshore

Winds blowing from the sea towards land are generally less than perfect. They increase the tendency of waves to topple earlier and in deeper water which can mean they're less steep and harder to surf. It can also mean the waves breaking and then reforming with no surfable wall connecting sections. These effects are much more pronounced on gently sloping beaches – a reef or steep beachbreak is largely immune to these problems. The second issue with onshore winds is that they create short period swell in the surf zone. The size of this will depend on the strength and duration of the wind as well as the distance over which it blows, but even on a local level a weak wind swell will create instability in the wave causing it to break in sections and generally offer more confused, less organised surfing conditions and this will happen on any kind of beach. There is an upside here: firstly that this can mitigate the tendencies of some beaches to close out and create peaks where none would otherwise exist. This same benefit, coupled with the general perception that onshore conditions aren't perfect, also means that onshore sessions will often feel a lot less crowded even on the most popular beach. Less people AND more peaks meaning a much better chance of getting your share.

Same bay different day. Even though the swell is larger you'll notice that the odd cleaner section is much more gently sloping. Even if you were to navigate this mess the waves you surfed would not only offer shorter rides, but have a lot less power.

Same bay different day. Even though the swell is larger you'll notice that the odd cleaner section is much more gently sloping. Even if you were to navigate this mess the waves you surfed would not only offer shorter rides, but have a lot less power.

Any questions or feedback on this feature please do give me a shout in the comments below.