Weekend Argus (Saturday Edition)
Steve Pike
WEATHER talk is one way to get sleepy Capetonians animated.
This weekend, sunshine dries out the sodden earth, and the waterfalls off the mountain are diminishing, in the wake of recent storm carnage.
There was endless heavy rain, weirdly freezing weather and huge east swell, all blamed upon a single mysterious entity: the cutoff low.
Surfers prick their ears up when a cutoff low is forming because it brings unusually easterly directions to the large swell that invariably hits the coast, which in turn brings excellent surf to spots that rarely break.
The definition of a cutoff low is a bit obtuse – often because they are described by weather boffins, who are often scientists with quite a crusty command of the English language. Of course, the storm itself is often met with the opposite – over- descriptive hyperbole and media hype.
Basically, the South African version of a cutoff low is a low- pressure system left behind when the upper level flow of air in the atmosphere shifts towards the pole. The system becomes disconnected from the jetstream, or “cut off ” from it.
The reason why we get too much of everything – from rain to wind to waves to plummeting temperatures – is that the system stays in one place for longer than usual, allowing it to build an exponential momentum. Most winter storms trundle along at speed, so the effects are brief.
Because the low- pressure system, often very close to the coast, lacks any steering air currents from above to pull it along the normal west to east trajectory, it gets stuck in one place, free to dish out its dire dose of mayhem. But the point is that the cutoff low is not a system in isolation.
The worst weather comes when a strong High- pressure system interfaces with the Low, as was the case this week when strong a high- pressure formed east of the low, over the eastern part of the country.
The cold anti- clockwise descending air of the High, in its attempt to move to the warmer, clockwise rising air of the Low, created an intense pressure gradient of SE to easterly gales between the two rotating systems – imagine a channel between two areas turning into each other.
Because the cutoff low was stuck in place in peak winter, the combined effects of the two weather systems brought bitter cold, snow, howling SE winds, and huge swell all along the East Coast.
There was unbelievable rain too. A town called Paddock, inland from the southern KZN town of Southbroom, recorded 400mm in one night.
There have been infamous examples of the cutoff low. For Durban, the worst in recent memory occurred in March 2007, when millions of rands in damage took place due to giant SE swell, coupled with a spring high tide and low- pressure storm surge.
But one of the worst storms in our history took place on Sunday, 31 August, 1902 in Port Elizabeth. The “Great Gale” wrecked no less than 18 ships in Algoa Bay, killing 58 people.
“Never before in its history has this port suffered under such overwhelming disaster as we record today. On Sunday morning some 38 craft rode at anchor under the leaden sky. Heavy rains had fallen and the wind gradually rose until, as the shadows of evening hid the shipping from view, a fresh gale was blowing in from the south- east, which, as the midnight hour was reached, had developed in to a hurricane. As the turmoil of wind and wave continued, so the toll of ships mounted, until 18 vessels were aground, with a raging sea adding a high toll of human lives.”
Be safe out there.
Enduro in Stellies
See you at the WP SRAM Gravity Enduro at Jonkershoek tomorrow, round 2 of the Western Province DH series. More info at www. facebook. com/ wpdownhill
QS Event
Our two CT surfers, Jordy Smith and Bianca Buitendag, have been eliminated from the Vans US Open of Surfing underway at Huntington Beach in California. Smith was knocked out in Round 3, while Buitendag fell away in Round 2.
Weather Tip
Today, fresh east offshores and a bit of surf 3’ maybe 4’ for fun waves, but False Bay looks miserable in fresh onshore. The wind goes offshore in False Bay tomorrow, but it looks small 2’ while the other side is small to flat and onshore. However, watch Monday, when an awesome new long range west swell arrives.