What makes a swell inconsistant?

[Revolution]

Sitting out in the surf today wondering where the waves went for 30 minutes i got to thinking... Why are some swells inconsistent and some are not.

I pretty much have a good grip of everything when it comes to swells / forecasting but never really knew why some swells are inconsistent with big lulls etc.

[2nd Reef]

Distance from the source Revo. When a swell is created it forms into sets, and the sets travel at slightly different speeds than each other.

The forerunners to a swell are the fastest moving, and the sets afterward a bit slower. The longer the swell is in the water the greater the time between sets and the more inconsistent the swell.

[oldman]

or on the other hand, the longer fetch longer period swells are actually far more consistent, in that they arrive at the beach at more regular intervals.

Now while revo might be thinking this is inconsistent, the close range wind swell which sends in a constant stream of waves, usually all over the place, with different periods, different heights and angles is probably far more inconsistent than the long period large fetch waves, which may arrive fairly regularly every 15 minutes with nothing in between.

[Nick Carroll]

^^they're both kinda right rev

In fact it has to do with swell decay.

Swells are best judged by period, ie the time between peaks. Among other things, the period is an indication of a swell train's speed, and its longevity -- ie how far it's able to travel from its source with a minimum loss of energy. in a storm fetch the periods are all mixed up in a vast pile of crazy shit. There's the 6-second windswell sea state stuff, the 10-11 second heaps-of-it-falling-over-each-other bit, the 14-second-nice-and-clean-and-long bit, and (if the wind's strong enough, tends to require 40 knots or more over a sustained time) the 17+ second muscular deep water travellers.

Once these swells begin to move away from the storm, they all begin to decay -- run out of steam. First to un-steam is the shortest period stuff; it's usually gone within a few hundred nm. The in-between stuff (where most of the wave power from any fetch is held, by the way) might make it 1600-1800 nm before pretty much being dispersed. 14-second gear (Indonesia's favourite) has several thousand miles in it, but loses impact rapidly after that. 17-20 second period swells can travel for many thousands of miles and retain their signature -- such swells have been tracked from the Southern Ocean near Heard Island between WA and Sth Africa all the way to Alaska, almost 18,000 miles!

What we're seeing along the east coast this morning is the faster longer-period swell, without any of the in-between stuff to fill the gaps. A lot of that died out before it got past Tassie, and what didn't will be 12-18 hours later than the first hit. By then of course that first hit will be in fcuken Tonga or somewhere.

The difference in period is amazing when you're in a place like SoCal and a south swell shows up from near NZ. The swell will last four or five days -- day one will be eight wave sets and 15 minute lulls, day two will be the best with shorter sets but way more of 'em, day three will be a moderating version of day two, day four will see a distinct lapse in power but still a lot of shorter waves, and day five will be a bunch of gutless crap.

[el rancho]

and we get excited over 12 second periods, yet in california 14-17 second periods are commonplace.

[oldman]

NC's sort of right there revo, but ..................

Nah, couldn't be bothered going there.

[Nick Carroll]

and we get excited over 12 second periods, yet in california 14-17 second periods are commonplace.

Yeah, but...a lot of the time, because some of our real swells come from powerful storms only a few hundred nm away, we get everything at once -- the whole deal. 8, 10-11, 14, 17, all dumping into the coast in a hail of swell. The long interval swell underlies the far more prominent mid interval stuff, where much of the storm's transferred energy is focused.

I tell you what, having experienced a fair bit of both, I would far rather a SE Oz weather bomb swell than a CA 17 second SW swell effort.

[el rancho]

yeah now that you mention it that does make sense for the east coast. we get alot of windswell in between the better sets of groundswell.

to be honest, sometimes surfing 6 second period swells can be great, everyone gets a buttload of waves.

actually, surfed Iluka few weeks ago and period was about 7 seconds coming NE from that storm cell that flooded the northern rivers. but it was super clean and the waves just kept on comin in, no waiting for sets at all.

[black duck]

yeah now that you mention it that does make sense for the east coast. we get alot of windswell in between the better sets of groundswell.

to be honest, sometimes surfing 6 second period swells can be great, everyone gets a buttload of waves.

actually, surfed Iluka few weeks ago and period was about 7 seconds coming NE from that storm cell that flooded the northern rivers. but it was super clean and the waves just kept on comin in, no waiting for sets at all.

Downside of the short period stuff is when you're surfing a beachy and you have to punch back out through continuous sets, no breaks. Endless duckdiving

[Grooter]

Pretty common to get 10+ periods in my neck of the woods, although that's to be expected considering the Mornington Peninsula faces in the direction of the Southern Ocean.

We had a crazy period down here about a month or so ago, I think it got close to 20 seconds.

[jimmy]

We had a crazy period down here about a month or so ago

My missus has them all the time..

[puurri]

Q; "What makes a swell inconsistant"
A: Poor spelling

FFS!!!!

[black duck]

Q; "What makes a swell inconsistant"
A: Poor spelling

FFS!!!!

Only 55 more posts Puurri, don't run out of ammo