El Nino not sighted, yet

Craig Brokensha
Swellnet Analysis

Last week the Bureau of Meteorology released an El Nino alert, but those of us on the East Coast might doubt that forecast.

After an average winter of surf, the last fortnight has been positively autumnal despite being smack bang in the middle of spring. We've had a run of good swells from the eastern quadrant with generally light winds instead of those dreaded north-easters.

And since the weekend a deepening coastal trough has squeezed a strong, stationary high resulting in torrential rain, gale-force onshore winds, and large storm surf. This synoptic setup is more typical of late summer.

All this rain and onshore wind is usually associated with La Nina - hence the skepticism over the El Nino prediction. However, this weather appears to be an outlier before we see the effects of El Nino kick in over summer.

El Nino events are typically associated with drier and warmer than normal weather across most of Australia, and this is where the current weather doesn't quite fit in.

This is because we're only at alert level, with signs of El Nino just starting to show in the tropical Pacific Ocean. All forecasts don't have it kicking in until December.

The deluge has been welcomed by farmers who were staring down another six months or so of dry weather, however it's been less well received by surfers, especially those in northern NSW and Queensland. Following six months of below-average waves there were many impressive sand deposits, yet this close-range swell event will eat away at them.

Word is that banks have been great from Byron to Newcastle (less so across southern NSW), but they'll now be reshaped, most likely into storm bars. Under storm conditions - such as we're seeing now - sand is gouged from the inshore banks, then deposited offshore as 'storm bars' which protect the local coastline from the greater impact of the swell. Great for halting erosion, terrible for surfing.

Current forecasts have the unseasonal weather and swell continuing into the end of the month, but how the banks fair after the current event is to be seen.

Comments

Chris Buykx's picture
Chris Buykx's picture
Chris Buykx commented Tuesday, 16 Oct 2018 at 4:14pm

Thanks Craig - I am not that concerned about storm bar formation messing up all the banks. IMHO short period swells from the E and NE do not move the sand around as much as a longer period groundswell from S (or any direction). A week of 4'-6' ENE windswell at 10 seconds would not have the same effect on deep storm bar formation as 1 day of 6' groundswell at 15 seconds. Swell period is everything to do with wavelength and therefore how much wave energy is acting on the sand at depth.

I reckon most of Northern Beaches, especially northern ends will actually find better sand distribution at the end of this week as the winter sand will be pushed back to a summer sand distribution. The Southern ends may end up with some sort of storm bar but nothing too serious

freeride76's picture
freeride76's picture
freeride76 commented Tuesday, 16 Oct 2018 at 4:39pm

It's the complete opposite effect here: short period storm surf is far more effective at storm bar formation and bank busting than long period groundswells.

I know the energy of a long period groundswell extends into far deeper water and I think that may in fact save the banks from the hammering they get from closer range, shorter period events, where the chaotic nature of the sea state and shorter period surf is more focussed on the inshore bathymetry as compared to long period swells where more of the energy can be absorbed in deeper sections of the shelf/slope.

Also, these storm surf events tend to be from the SE to ENE direction , which is a far more direct hit on the coastline and "punches holes" in the banks. Once the integrity of the bank is breached the water flow in a storm surf state gets in behind it very quickly and scours it out.

Whereas long period events tend to be more from the S where the effect of the lee shore and refraction shelters the banks somewhat.
Also long period events from the S here tend to move the sand in slugs, and most of that slug tends to settle inshore somewhere and not as a storm bar.

donweather's picture
donweather's picture
donweather commented Sunday, 21 Oct 2018 at 5:59pm

Couldn't agree more Steve. How have the banks faired down your way?

Craig's picture
Craig's picture
Craig commented Tuesday, 16 Oct 2018 at 4:46pm

Yeah I'm with Steve on this one, I reckon those longer-period more organised swells come in organised onto the banks and don't really change much at all.

But when you have all this storm forced wave run-up and irregular wave action impacting with such consistency it really rips things apart and stirs it up.

Smaller periods of north-east windswells seems to put sand into the southern ends, but these larger swells, not so much.

dandob's picture
dandob's picture
dandob commented Sunday, 21 Oct 2018 at 10:03am

Well I won't pretend to know the science behind it all but I can tell you that the banks where I live are all totally farked.

Chris Buykx's picture
Chris Buykx's picture
Chris Buykx commented Tuesday, 16 Oct 2018 at 5:39pm

Its all a matter of perspective i.e.: where you are!
If you are looking at NNSW or SE Qld point break, then sand accretion in the lee of the point happens during winter with predominant S to SE swells. The sand transport to the N around the headland fills in the holes and long period groundswells smooth out long even bars that peel.
However an ENE storm or wind swell hits the point head and becomes erosive - and breaks up those nice banks running down the point. The bank buster is a feature of the North Coast and SEQ. It does not apply further south.
You can read more on the differences between the north cost and Sydney and the South Coast here:
https://www.swellnet.com/news/coastal-creationism/2016/02/09/coastal-cre...

I wrote my first comment from my perspective on the Northern Beaches of Sydney - where South Groundswells are erosive. The winter pattern is for the SE facing beaches to absorb that energy and so the beach shrinks, storm bars form and there is a general lack of sand that results in good banks. But the summertime pattern is accretionary - i.e.: shorter period swells from the ENE move the sand back in to our wave zones and instead of deep channels and straight bars, we get broad, even sloping banks with shifting rips resulting in fun beachies!

Lanky Dean's picture
Lanky Dean's picture
Lanky Dean commented Wednesday, 17 Oct 2018 at 2:42pm

Chris , have you ever spent anytime on the north shore of Oahu?
Its amazing to watch what happens to the sand there over an eight month period.
Pretty wild !

The Fire's picture
The Fire's picture
The Fire commented Tuesday, 16 Oct 2018 at 8:35pm

Yes!!

I learnt a new word..

Accretion.

Peace maaaan..

Mort's picture
Mort's picture
Mort commented Wednesday, 17 Oct 2018 at 12:35am

That means shit right?

crg's picture
crg's picture
crg commented Tuesday, 16 Oct 2018 at 9:23pm

Short duration storm swells can sometimes have a positive effect on banks, breaking them up a little and creating nicely tapered edges but bigger or more sustained storms are death knells. It took about 18 months I reckon after that massive black NE swell for the storm banks in NNsw to break up fully and re-deposit along the shoreline.

I'm not cheap,
But I'm free.

freeride76's picture
freeride76's picture
freeride76 commented Tuesday, 16 Oct 2018 at 10:09pm

yeah, we paid heavily for that one.

STENKEL's picture
STENKEL's picture
STENKEL commented Tuesday, 16 Oct 2018 at 11:28pm

what is sand ?

Mort's picture
Mort's picture
Mort commented Wednesday, 17 Oct 2018 at 12:34am

It is little jewels of wonder.

The Fire's picture
The Fire's picture
The Fire commented Wednesday, 17 Oct 2018 at 5:03pm

Sand is crushed up whale bones.

Peace maaaan..

velocityjohnno's picture
velocityjohnno's picture
velocityjohnno commented Wednesday, 17 Oct 2018 at 6:13pm

It's what these little guys poo out when they eat coral:

https://www.youtube.com/watch?v=7nm-t3ZpFGU

Mort's picture
Mort's picture
Mort commented Wednesday, 17 Oct 2018 at 12:33am

I am like the Pirate on the Crows Nest, I am peering. I can't see shit.

Mort's picture
Mort's picture
Mort commented Wednesday, 17 Oct 2018 at 12:37am

I will tell you when I see something.

Mort's picture
Mort's picture
Mort commented Wednesday, 17 Oct 2018 at 12:41am

Here's a Poem
She will come upon you
You will not no her name
But still
She will come upon you.

tidak_bagus's picture
tidak_bagus's picture
tidak_bagus commented Wednesday, 17 Oct 2018 at 11:58am

Well we had a La Nina summer last year that felt much more like an El Nino, very little to no rain and scorching temperatures. The topsey turvey continues.

Lanky Dean's picture
Lanky Dean's picture
Lanky Dean commented Wednesday, 17 Oct 2018 at 2:39pm

Well I think you are all correct!
Each swell that hits the east coast is usually deemed southerly, south east , east and north east.

Maybe it would be in your best interest to start a log book and document each swell event /angle /period / height/ duration.

I think most surfers do that (undocumented).What's not usually accounted for is the amount of rain fall on land that then returns to the ocean via lakes ,streams, storm water , rivers, creeks , ect.

A large majority of waves I grew up surfing don't break the same now days. Numerous reasons why, sand replacement and lack of proper erosion being one reason. New buildings changing wind and water patterns being another.
Banks come and banks go. Some times the banks don't return for many moons .

Ralph's picture
Ralph's picture
Ralph commented Wednesday, 17 Oct 2018 at 4:51pm

Storm bars have formed at my local beaches. With the short period waves coming in at fairly high frequency I'm finding it a bit harder paddling out this week :)