Many powerful tropical cyclones have made headlines throughout 2018, particularly in the United States. Although tropical cyclones, or hurricanes, are rare to southern Africa,Senior Lecturer in Physical Geography at the University of the Witwatersrand, believes this may soon change.
Fitchett recently noted a change in the South Indian Ocean – which surrounds South Africa – that may make conditions conducive these natural disasters.
“As my new research shows, the trend in the South Indian Ocean is shifting. Category 5 tropical cyclones didn’t exist in this ocean before 1994. They were recorded for the North Atlantic, North Pacific and South Pacific Oceans throughout most of the 20th century. But since 1994, category 5 storms in the South Indian Ocean have become more frequent,”
When cyclones hit in the southern African region, they tend to be of quite a low intensity on the Saffir Simpson scale, usually ranking ‘1’ on the scale.
Category 1 storms are smaller in diameter, 50-100 kilometres, and have a minimum wind speed of 119 kilometres per hour, while category 5 storms have wind speeds of 252 kilometres per hour or more and can span up to 500 kilometres in diameter.
Category 5 hurricanes did not occur in the South Indian Ocean before 1994, but have steadily increased in frequency as the years have gone by.
“Based on the progressive trend over the past three decades, their frequency is likely to keep increasing,” Fitchett says. “This is happening because sea surface temperatures are rising. Tropical cyclones require a minimum sea surface temperature of 26°C in to form. These temperatures are being recorded more often and over a larger area of the ocean now than in the past. That’s because the air temperatures that heat up the sea surface are rising due to greenhouse gas emissions.”
“Southern African governments must respond proactively to this new threat,” she adds.
The last time a category 5 storm hit southern Africa was in April 2016, when tropical cyclone Fantala moved through the southwest Indian Ocean, passing north of Madagascar and making landfall on the Island of Farquhar in the Seychelles.
“Unfortunately, southern Africa struggles to cope with the effects of even category 1 tropical cyclones. This suggests that governments are ill-equipped to deal with the more powerful category 5 variety,” Fitchett says. “But there are things that can be done to proactively deal with this new climatic reality. For instance, coastal buildings, roads and bridges need to be built to withstand the high wind speeds, heavy rainfall and possible storm surges to prevent costly damage to infrastructure.”
Fitchett recommends that better forecasting systems be implemented, so that towns and cities can evacuate more effectively to prevent the loss of human life.
“Spatial planning needs to consider this heightened threat, and where possible, discourage development along with high-risk coastlines,” she adds.
Souce: The Conversation