Steve Pike

Weekend Argus (Saturday Edition) - - LIFE -

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.

HOW DO YOU LIKE THAT? Coco Ho of Hawaii dur­ing her Round 1 heat at the Vans US Open last week.

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