West OZ Waves- The Indian Ocean gift

The second ingredient which makes Geraldton one of the best places to windsurf and kite are the waves.

Each time again it is a thrill to wake up in the night by the increasing sound of thunder. A new swell is arriving. Is it going to be a big one? Is there going to be enough wind? How long does it stay and what is the peak period? Damn, I can not sleep anymore, better fix that ding in my board before it is too late….

There are many types of waves in the world. You have Seas, swell, storm swell, freak waves, tidal waves, Tsunamis and cyclone swell to name a few.

Before we explain which wave/swell conditions are good (see local sailing hot spots page), we first need to make one thing clear. Different spots work better with different swell/seas. Therefore it is handy to know what it going on so that you can be on the right spot at the right time. We will now explain the difference between seas and swell

Seas

Sea waves are caused by local winds. They are created relatively close to shore and are very disorganized. In countries like the Netherlands, Belgium or Germany and on all the lakes you mostly get seas. Seas can get big. Depending on the wind strength and the direction you can get seas of up to 6 meters. Once the seas travel a bit they can form sets. Usually you have a set of 3 to 4 waves, where the third wave is the biggest. Sailing wise it is quite full on to sail in large seas.

Example of onshore seas: Mick Steffan back in 1997 in the North Sea doing a one handed table top, The Netherlands, Zandvoort, February, 6 degrees air, 6 degrees water temperature. Enjoy it? Of course you do.Airborne

Swell

West Oz Swell waves are created by distant storms in the roaring 40ies in the Southern Ocean. Swell is created by huge storms where the low pressure systems are the strongest.. Sometimes in winter or early spring you can follow one of those low-pressure systems for weeks around the globe, creating swells up to 40 foot. Two years ago a low pressure system went around the globe twice creating one of the biggest swells of the last few years. When the swell arrived in Geraldton, the wave boys where indicating 7 meter swells. Generally it takes about 6 weeks for a low-pressure system to go around the world. The swell gets bigger if the fetch period is longer. In other words, if a low pressure system produces a long time a strong wind, say 80 knots plus, the sea created by the wind gets higher in size. Now, after the sea travels out of the storm field it becomes a swell. The energy of the waves groups together in swell sets. When the waves travel a long time the time between one wave and the other increases. This is called the wave period. A typical summer swell last only for a day or two while a winter swell can last a whole week. The wave period increases to about 14 seconds in an average summer swell while seas have a wave period of less than 7 seconds.

Going back to West Oz, once these swells hit the bottom of the West Oz continent it increases in size, but also decreases in thickness. Generally a 2 meter swell produces local high waves (3/4 mast high faces) while a 3 meter swell produces about 1,1/4 quarter mast high faces.

Now lets talk about the shallowness where a swell breaks in. A swell generally breaks when the dept at the swell is 1.5 times the height of the swell. So a 3 meter swell breaks in about 4.5 meter of water.

Finally if you want to use the right surf terms to describe the size of the breaking waves we can use three measures. You can use feet (general measure) or (ankle high, mastfoot high, half mast, loco high, mast high etc (windsurfing) or chest high (~3-4 ft), head-high (~5-6 ft.), overhead (~7-9 ft.) or double overhead (~10-12 ft.) (when surfing)

Waves and Surf Forecasting

Of course there are many other factors which determine the wave size. However in order to help you predict the waves in Geraldton you should consider the following facts.
  • Swell breaks when the dept is 1.5 times its height.
  • For every 1 day of travel time the height of the swell will decrease by 30%
  • It takes about 6 days for a low pressure system to pass from the top of South Africa to Australia while it takes about 6 hours to get a new swell that arrives from Down South (Margaret River wave boy))
  • Waves with a West wave direction will hit the Abrohlos Islands, A group of Islands 65 km west of Geraldton.
  • The distance between Geraldton and the drop of the continental shell is about 70 km
  • Between Geraldton and the Abrohlos the average dept is 50 meters.


Together with the links to the Wind and Swell forecast sites you can now attempt to forecast the swell height. It could be anywhere between ankle high and double mast) Good Luck!!

Which sailing spots with which conditions?

Geraldton area has over 10 sailing spots. To come to Australia and use Geraldton as a base is most likely your best option to get good sailing. Depending on your skills and what you like you can go jumping at Coronations or ride some big waves at Hells Gate, Point Moore. Just check out the sailing hot spots section for the pick of your day. Happy sailing!!

 
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