Analysing the East Coast flat spell
Winter: was that it..?
Australia's eastern states have just exited the worst winter surf season in recent history. Besides last week's quick pulse of tradeswell, East Coast surfers have spent the last five weeks surviving on intermittent windswell between bouts of abject flatness. If you're a Sydney surfer and you've seen a wave over three feet you can count yourself lucky.
So, the question has to be asked: What is causing the recent lack of waves? And while we're here we'll ask this question too: Is there a connection with the frustratingly excellent surf the Southern states have experienced during the same period?
Before we begin, it must be noted that we are scientists, and as such, are rooted in the Western scientific tradition of rigorous testing and applied logic. Now, with that out of the way let's talk Chinese philosophy...
The idea of yin and yang is a model we can use to make sense of the recent winter. The concept goes like this: opposite forces are interconnected and complimentary of each other. For instance, there can't be light without dark, good without bad, and in Australia's current swell state, good waves in the southern states without bastard flatness in the east.
The reason for the contrast in wave activity across the continent is the positioning of the Southern Ocean storm track. To wit, it has stalled and focused it's energy squarely up towards Western Australia, Southern Australia, and Victoria for over a month.
So there you have the yin - the light, the good. What about the yang and all it's depressing connotations?
It's important to realise that Southern Ocean storms don't follow a straight path around the globe. The path they follow is more like an up and down roller coaster, and it's guided by the Long Wave Trough and upper level blocking patterns. Recently the 'up' of the roller coaster has been located just under South Western WA and it's created multiple swell trains aimed at the southern states.
Unfortunately, for East Coast surfers at least, the 'down' of the roller coaster has been located just east of the Great Australian Bight and it's sent storm activity – storms that would otherwise create waves for the East Coast - south and away from Australia. The current configuration of the storm track has effectively cut off the East Coast's southern swell machine.
Now, this setup isn't always detrimental to the East Coast, as during warmer months low pressure systems can develop to our east topping up the swell ledger with straight easterly lines. However, during winter the chances of this scenario are much lower and what usually results is a benign Tasman Sea with bouncy intermittent windswell and not much else. The yang – the dark, the bad.
The good news is that despite the apparent stasis things will change and the yin will invariably become the yang. When the East Coast's southern swell engine fires up it'll signal an upcoming spell of small waves and poor winds for the southern states. All because the storm track will be guided away from their swell window.
These patterns rarely last more than a couple of weeks before switching back. And this is what makes the recent lack of swell (or run of swell depending on which part of the country you live) stand out – it's persisted far longer than usual. To make matters worse, after five weeks without waves the East Coast is now heading into spring, traditionally the most quiet time for surf. Might be the right time to start reading more Chinese philosophy. //CRAIG BROKENSHA and STU NETTLE (who isn't really a scientist but just helped out with the wordy bits)