Deceptively powerful surf conditions

[foulhooked]

On the BOM website it says for today (saturday 9/8/14) there are deceptively powerful surf conditions. However when i look at willy weather, it says 1.1-1.3m seas and a period of roughly 13 seconds. I would have thought this would result in fairly calm seas.

My theory now is that with a higher period in the waves, the more water volume the waves have, resulting in a more powerful wave when it hits the rocks?

Is this true? or is it something else. Just curious...

[batfishing]

There was a good lumpy swell running today, it was a long way apart, so no issue when out. Some of the swell that was running though had some good volume in it.

Basically at the beach or rocks this can result in the odd big long rolling wave coming up. Hence why they said surf could be unpredictable.

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[JimT]

plus big tides as well

[kingiemaster]

The BOM warnings are beginning to be a bit like the boy who cried wolf. I fished off the rocks today from 1030. No probs. two other fishos had been there since 7am at high tide and they said it was fine also. Plenty of blackies as well.

[batfishing]

The BOM warnings are beginning to be a bit like the boy who cried wolf. I fished off the rocks today from 1030. No probs. two other fishos had been there since 7am at high tide and they said it was fine also. Plenty of blackies as well.

Today I could understand.

Yesterday though, they were probably correct.

When we went out in the morning. There was a surf break inside Port Hacking. As we got in line with Jibbon Point, a wave over 3M stood up on our starboard side, it was a good 150M in length, the break over the bommie was also substantial

By the time we came back in at 3.30, it was glass

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Edited August 10, 2014 by Ian Bat

[Sydneyfisher12]

Yesterday (Saturday) the platform off north head was underwater with white wash when a wave came through you would have a death wish to fish there also old mans hat was the same

Both spot were very dangerous

[krause]

Always use caution in times like these. Big swell periods are deceptively dangerous. Also be aware in, times of sudden change in swell period, change in swell dirrection and shifting weather patterns like now. These times spawn true freak waves, which often hit without any warning. Its up to each fishermans judgement, but use caution. I learnt the hard way, I dont wish that on anyone else. Stay smart

Cheers

[Jimbu]

Swell forecasts are notoriously unreliable; the swells often arrive late or early, and particularly with acute angle swells such as typical winter South swells, some spots will receive the full brunt while others will miss it. This depends not only on the direction the spot is facing and the period length of the swell, but also upon the bathometry (sea floor geometry) between the swell source and each break.

For example, a long range swell travelling through deep water that suddenly becomes shallow will be magnified significantly.

For these reasons,I think the BOM would err on the side of caution with their warnings.

All it takes is one rogue set to make a dangerous situation...