Roads in Port Alfred and Amsterdamhoek on the Swartkops River near Port Elizabeth were flooded earlier today, as an unusual weather phenonemon struck coastal areas. Garth Sampson, Client Liaison Officer for the South African Weather Service (Eastern Cape Region) said coastal surges were relatively rare and happened when certain weather conditions occurred at more or less the same time.
“One must have a spring high tide, high seas and strong westerly winds,” Sampson explained.
Sampson, who is based in Port Elizabeth, said it was the first time, other than during floods, that he had seen the roads in Amsterdamhoek flooded. Had the winds turned onshore, the N2 would also have been flooded, as was the case on 1 September 2008, he said.
Sampson said the passage of the cold front yesterday, in combination with a steeply ridging high pressure system behind it, resulted in gale force winds which in turn caused high sea conditions of between 6 and 9 metres out to sea.
Simultaneously there had been a spring high tide which further enhanced the wave heights and resulted in a storm surge along the coast between Plettenberg Bay and East London.
“The passage of a cold front on Monday 28 October 2019, with a high pressure steeply ridging behind it resulted in gale force winds, thus high sea conditions (6-9m),” Sampson said. “Simultaneously, a new moon was expected and thus enhancing the wave heights and resulting in a storm surge in places along the coast between Plettenberg Bay and East London.”
The forecasters on duty issued a threshold warning for both the gale force winds and high seas warning for the public on Sunday, while a wind and wave impact based warning was sent out to the relevant municipal officials on the same day.
“These conditions are expected to start subsiding from tonight, with the wave heights still expected to be between 4.5 to 5.5m tomorrow,” Sampson said.
Abnormal waves remained possible in the Agulhas Current between Port Alfred and East London from this afternoon until tomorrow morning, possibly causing coastal inundation, damage to vessels and affecting coastal recreational activities.