Onwards and Upwards: Notes from an Incredible Swell
Wednesday's oversized East Coast swell produced one of the more memorable wave traces across the MHL network of waverider buoys.
As per the image to the right, you can see that the maximum wave heights at the Sydney buoy shot up from approximately 3 metres at 5pm, to over 12 metres by 6pm. This is an astonishing 9 metre increase in one hour, or 1.5 metres every ten minutes. A horrifying place to be if you were in a boat, that's for sure.
Incredibly, the trend replicated itself right along the eastern seaboard. The waverider buoy at Crowdy Head recorded the exact same 'J-curve' at about 1am, whilst the buoy at Byron Bay recorded a similar leap in size at 10am. Every location saw maximum wave heights increase in the order of 8-9m within the space of about an hour or so.
And this is where things get interesting. If we ballpark the travel distance between the Sydney, Crowdy Head and Byron Bay buoys (relative to the regional swell direction, of course), and estimate the swell's speed by its period, we find that the swell travelled north at approximately 32km/hr.
Also, if we ballpark the speed of the southerly change associated with this swell event (which was itself the byproduct of an East Coast Low), we also find that the change apparently tracked northwards at approximately 35km/hr.
This is enough evidence to suggest that a 'captured fetch' may have been responsible for the very large and rapid increase in wave heights. A captured fetch is a phenomena where a storm moves in the same direction and at the same speed as the swell it's generating. This significantly amplifies wave heights compared to what we'd typically expect from a storm displaying equal strength, but with a less favourable forward track.
Because the swell increase in Sydney waters occurred during the cover of darkness, we're unable to verify the size translation at the beach. However, we've received many reports from Northern NSW and SE Qld - where the swell arrived throughout the day - from surfers who were in the water as wave heights increased from 1ft to 6-8ft within an hour or two. Despite all the amazing buoy readings, this was not a quality swell in surfers terms and only a handfull of places were rideable. The reason for that is another article in itself. //BEN MATSON - CRAIG BROKENSHA
Comments
How do southerly winds of 100+km/h travel north at 35 km/h ?
All I can think of is they are spiraling upward @ 100k's, but the system as a whole is moving at 35k's. Correct?
That's a very complicated question, shoredump - and we're probably not the most qualified people to answer it (I'll see if one of our mates at Weatherzone can chip in). However, you're on the right track - surface wind speeds/gusts are often related to characteristics within the atmosphere's vertical profile.
This technical stuff is a bit out of my comfort zone, but I think Shoredump is basically right.
The wind is rushing at 100km/h towards the centre of the low, but the central pt of the low (i.e. the lowest pressure - presumably the actual pressure nadir is at elevation for lows and maximum at SL for highs?) is moving itself in a horizontal plane.
So it is 'the change' or position of the low that is moving at 35 km/h.
Question for the forecasters: I know these are ballpark figures, but if the position of the low actually overtakes the swell train then it could kill it, I gather. Did this happen on the Sth Coast?
Awesome stuff Craig thanks for the summary.
alakaboo, actually the problem on the South Coast was that it was a little too close to the source fetch. The parent low initially stalled near Eden (with S/SE gales aimed mainly into the Gippsland), however once the low eventually pushed to the northeast (ie as the trough retreated back into the Tasman), it took some time for the sea state to become fully developed.
As you suggested, the storm ended up moving out of the South Coast's swell window too early for the full effect to be felt, like we saw in Sydney. It would appear that Sydney was perfectly positioned to cop the largest combination of swell energy from this event - both short and mid range. We can only go via the available buoy data, however Hmax data from the Crowdy and Byron buoys was 3m and 4m less than that of Sydney - mainly due to the lower surface wind speeds near those locations (and therefore a subsequent smaller loading of local windswell).
However, all of this discussion is mainly about open ocean swell size, as measured by the MHL buoys. If you're talking about how this energy translated to surf size at the beach, then that's probably worth another article! There are many reasons why we saw such a wide range of wave heights right across the entire NSW coast.
Ah, yes. Forgot about the simple explanation for the Sth coast. I'll stick to my day job.
Hey Everyone,
Interestingly enough - what else happened on the 6th June 2012. It was the transit of Venus across the face of the sun. As surfers we know that they sea has a connection with the moon as it moves in sync with the tides. The transits of Venus occurs in a pattern that repeats every 243 years so if anyone has history of the swell dating back to 1769 we could see it have happened previously. The 6th June 2012 transit is our last opportunity to observe a transit of Venus, as the next event occurs on 11th December 2117, so some one start recording the data and we will look in another 243 years!
Cheers
Hey Flowrider.
What is 'the data'???
I think it's fair to assume that astronomical events don't just have an effect upon the Tasman Sea. So YOU could start by comparing global pressure charts or something over maybe the last 10 years, to see if June the 6th was actually extra special in the first place. There's no point in spouting theories that obviously can't be proven wrong, so do something about it if you really are interested.
http://www.bom.gov.au/australia/charts/archive/index.shtml
Hi Shoredump,
You've kind of answered your own question when talking about the vertical structure of the weather system.
At the edge of the advancing front, the interaction between the two air masses leads to increased instability and gusts within the storm which reach the surface and blow in the direction of the storm but only temporarily in time.
Also as Alakaboo mentioned the circulation around the low is quicker than the movement of the low itself, much like a cyclone where we get extremely strong winds around the cyclone centre but the cyclone itself moves much slower.
And I'll look into the archives for that one flowrider!
6-6-1769 some guy surfed 10' Lennox and had it all to himself.
I didn't find anything special in Cookie's journal, but feel free to prove me wrong as I only skim read.
http://ebooks.adelaide.edu.au/c/cook/james/c77j/chapter3.html
Hi Mitchvg
Firstly, I have know right in making you believe my theories. I have done the work and proved to satisfaction that the world is simple, based on exact mathematic proportions. Whether if you believe in science or not we can all agree that whatever career you are situated in we all come up with the same number in mathematics. In regards to data I need records of data just like the one that was posted in the article to add to the confirmation of my studies.
For the past couple of years I have devoted research and attention to the idea of history repeating. Like many others, I have been down paths that have lead me nowhere, and it was only when I began discovering the natural laws of science and mathematics that allowed me to investigate the theory behind the cyclic nature of any discipline.
The exploration of fundamental science and mathematical laws, lead me to discover the idea behind the Law of Vibration. The Law of Vibration is the fundamental law upon which wireless telegraphy, wireless telephone and phonographs are based. Without the existence of this law, the above inventions would have been impossible.
I believe that in any discipline, itself exists as a harmonic or in-harmonic relationship to the driving power or force behind it. Everything in this universe are live electrons, atoms, and molecules, which hold persistently to their own individuality in response to the fundamental Law of Vibration. Science teaches ‘that an original impulse of any kind finally resolves itself into periodic or rhythmical motion, just as the pendulum returns again in its swing, just as the moon returns in its orbit, just as the seasonal cycle of a year, so do the properties of the elements periodically recur as the weight of the atoms rises.
Science has laid down the principles that ‘the properties of an element are a periodic function of its atomic weight.’ A famous scientist has stated that:
“We are bought to the conviction that diversity in phenomenal nature in its different kingdoms, is most intimately associated with numerical relationships. The numbers are not intermixed, chaotically and accidentally, but are subject to regular periodicity. The changes are also seen to be in many cases adulatory.â€
- Michael Faraday
Thus, one can say that every class of phenomena, whether natural or other disciplinary must be subject to the universal law of causation and harmony. Every effect must have an adequate cause.
Therefore, the repetitive nature of any discipline, we must deal with causes. Everything in existence is based on exact proportion and perfect relationship. There is no random chance in nature, because mathematical principles of the highest order lie at the foundation of all things (Faraday, 1909). Faraday said: “there is nothing in the Universe but mathematical points of force.â€
But before going any further, the concept of ‘History Repeating’ is debatable, but great evident of history repeating is War. History proves that wars break out every 20 to 25 years It also proves that there is a great wave of speculation and a boom of some kind in nearly every country every 20 to 25 years (GFC stock market crash – 2007 previously happened in 1987 – 20 years ago!). So, why do these war periods and boom times come at such regular cycles? The main cause is that “human nature never changes†.Every 20 years a new generation comes along. They are full of hope, optimistic and are progressive and up-to-date. They are also inexperienced. They do not know the bitterness of war, and they have never been in a fight. However, they are anxious to get into one. It is easy for the politicians to get the young men to go to war but not the old fellows who have experienced it.
This repetitive cycle is evident in every field. Whether, a boom in business or a boom in architecture, the young has to be served and young nature has to have its fling. Concluding, that history ultimately repeats because, “human nature never changes†and every young generation have to go through the same experience as the former generation did.
The warming and cooling of the earth has been occurring for millions of years. If you search history, you will see there was a 200-year drought in 800 AD, when the South American Mayan civilisation collapsed.
Sunspot cycles
Inigo Jones’ theory is based on the idea that the solar system is simply a vast electromagnetic machine that is automatically controlled by the magnetic fields of the planets. Sunspot cycles are on average the same length as the cycle of Jupiter –11.86 years
Might sound gloomy, but why is the earth here or why are we here in the first place?
Can you sum all that up in one sentence flowrider?
Shirley Bassey Can
&feature=fvwrelGood post flow rider, I reckon your theories have reason and are valid. We are born , we live , we surf and eventually we die. Simply cyclical, but why?
Flowrider.
That's all good. But this particular example will be more convincing with a basic attempt at substantiating it with any sort of indirect approach.
Flowrider, you're not a disciple of Ken Ring's work are you?