Shattering The Glass
Adelaide surfers enjoyed an incredible sunset last Thursday; the twilight reflecting off a glassy, still ocean.
It was the perfect end to a sweltering 40°C day.
Just on dark though, a relieving and late sea breeze kicked in, dropping temperatures slightly before a cooler change arrived through the early hours of Friday morning.
Our Triggs surfcam caught the late arriving sea breeze on the South Australian Mid Coast, with the tell tale wind disturbances slowly creeping in from the horizon to the west.
This slow creep of texture usually signals the end to the surf for the day, with the offshore land breezes succumbing to an onshore flow, quickly adding bumps and crumbling the waves that were clean only minutes earlier.
What's fascinating in the captured footage are the glassy patches which seemed to be jumped over, as the sea breeze advances towards the coast.
Different to parallel running wind streaks which form under strong, steady winds from a constant direction, these glassy patches are linked to areas of still air, while around them the surface is ruffled due to the westerly sea breeze.
In normal cases, the sea breeze front arrives in a clear, defined line, but there can be other factors at play.
Firstly, an understanding that sea breezes develop thanks to the differential heating of the land compared to the ocean during the day. The land heats quicker than the ocean, resulting in rising air and lower pressure developing on the land mass.
Cooler, more humid, dense air fills in from the ocean to replace the rising air, and this is known as the sea breeze.
Being denser, this air slides in underneath the rising, warm air, though mixing occurs under the nose of this front, producing local scale downdrafts and updrafts. This is likely what's shown in the above video.
Cool sea breeze (blue) flowing in, under warmer ascending air off the land (red). (Sea Breeze: Structure, Forecasting and Impacts)
Weak currents can also create surface tension which overrides the surface winds below a certain threshold.
By the time you spot the sea breeze encroaching out to sea, you have little time left to catch those final clean runners before it hits.
Comments
Wonder what went through those blokes heads when they saw the sea breeze coming?
Probs ‘oh for f¥€*k sake‘.
I'd have a guess that they were dreaming of places further afield, not blocked by Kangaroo Island.
dusk surf on the mid? probably thinking tk fk got away with another one
Ha ha! Sadly, the only experience I've had with SA was visiting a family friend as a kid at their house in Henly Beach.
Those colours are nice and as the sun set on a scorching hot day, I reckon it would have been a pretty nice place to be.
They would have been forlornly hoping for a set over 1ft.
What is represented on the the surface of the water can be misleading.
There is not only one flow of air across but also up an down.
Imagine the very front of a rolling white water after a wave has crash and settled into itself.
Whilst the average direction and energy is moving in a consistent way the reality is that there is a turbulence.
As a sailor and a flyer I can picture those calmer areas as lift and downdraught.
Exactly MiddleMan.
Ripper sunset sadly enhanced by the smoke from the Port Lincoln fire that day. Those streaks on the ocean are very common in Streaky Bay, hence the name.
Indeed, travelling parallel with the wind, but this is a different phenomena and more perpendicular to the wind.
Firstly it's a great capture thx. I'd be happy to see my local Vic beach looking like that and to catch the change like that is totally cool.
If you pause it at 6seconds you see a 'four and twenty moment'. Our sunset surfers thinking about dinner get surprised by the only wave on the horizon
I drove past triggs on the way home from work that day about 1.30 pm. At that stage the tide was low and the waves were barely ankle high, it was stinking hot and I nearly threw up upon seeing two logger chicks climbing into 4mm f bomb steamers. I overheat in boardies and long sleeve rashie. Sunday arvo really picked up and was the strongest swell I've seen here for some time. Scored long head high lefts with only a couple of other punters at censored.
Yeah Sunday's swell was a goody eh!
"nearly threw up upon seeing two logger chicks climbing...."
" I overheat in boardies ...was the strongest swell I've seen here for some time.... "
"Likely linked to the lingering Niña ..."
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on ya Craig , it was an amazing evening. went out on the boat about 5 and what isn't shown on the video is the amazing virga rain phenomena that was around leading up to sunset, although a few drops touched down out in the water ( I assume also on land ). we could see the wind line approaching from higher ground as we left Sully's. this is a precedented but amazing phenomena with a NW change during summer when it hits at 30 plus knots.
this february has been pretty atypical on the mid which usually features a 3 week spell of pool table flat and trade SE winds. we had shoulder high sets sunday arvo. maybe you could comment Craig
cheers frank
Thanks Frank! I saw the virga sunset on socials! Looked incredible. I'm sure my friend Min wouldn't mind me sharing her images below..
surreal!
beautifully captured, was like fire on the horizon, with incongruent but welcome drops of rain. any thoughts on the atypical February patterns?
Likely linked to the lingering Niña trend throughout the Pacific Frank.
My minds eye still reminds me of a session at U Turns
rights
Long time ago that was for U turns very respectable and seeing a bloke takeoff on a backlit head high wave and by the end of the wave the wind had fucked it .
Reminds me of a surf late last year. Long hot drive from work to the coast, pull into the carpark to see pleasant glassy 3 foot peelers. You could see the dark line out there, a change rather than sea breeze, but someway off the coast. Rushed to get suited and out there, duck dived the first bit of whitewater only to be hit in the face by the wind on surfacing. Was destroyed by the time I made it to the peak. Bugger.
Great footage.
Ha, that's cruel!
Yeah Blackers, used to live there and saw that more than once. Sometimes the northerly coming would be so strong and defined that as well as seeing it come down the Gulf you could hear the chop hissing well in advance as it got closer. As soon as it hit the usually small waves were completely destroyed. :-(
beautiful!
Strange place the mid. Had many uncrowded glassy surfs over the years in the early arvo on stinking hot days after the northerly has crept down the gulf and blown it out earlier in the day and everyone has bailed. Not many places in the world either where the hotter the day the lighter the sea breeze. What’s up with that Craig?
Usually under those really hot days, winds are strong out of the north, so they override the sea breeze effect, with a quasi balance establishing resulting in glassy, stillness.
That was my first day living in Adelaide. Took the kids for a swim and fish and chips and got some ice cold droplets of rain. Awesome arvo though, way to set the bar for a change from the Cairns Esplanade or Palm Cove for fish and chips and ice cream
How good!
A bit left field to this topic, but maybe somewhat related..
I've noticed that on the NSW North Coast / Gold Coast when the synoptic is set up such that we have the wind coming from generally south of east often the wind will clock more south as the day goes on. Often to the point where it can go quite light south by close of play. Then the next morning back to the ESE again. I wonder if there could there be a similar explanation for this? (Or if I'm seeing patterns that actually aren't there!)
Not sure DP, but further south of where you are, if the wind is south west or south in the morning it will gradually swing to the south east during the day (ie opposite of your obs!) and almost everywhere will be on shore by the arvo.
Fish Frank?
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A bit far left field to this topic, but maybe somewhat related..
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