An intense cold front is expected to bring a mid-latitude cyclone to parts of Cape Town on Sunday, 7 July 2024, resulting in severe weather conditions.
Mid-latitude cyclone expected in the parts of Cape Town
This weather system is expected to bring a significant drop in atmospheric pressure, strong winds, high waves, and storm surges along the west and southeast coastlines of South Africa.
The cyclone is anticipated to undergo rapid intensification, with the central sea-level pressure dropping by more than 20 hPa over the next 24 hours.
This pressure drop, combined with strong northwesterly to westerly winds, will lead to gale to strong gale force conditions, particularly along the coast.
Wave heights are expected to reach between 6-8 metres, potentially reaching up to 10 metres in some areas, with the most severe conditions forecasted for the southwest coast.
Heavy rainfall is also expected, resulting in localised flooding, damage to coastal infrastructure, and disruptions to daily activities.
Recreational areas near beaches are at significant risk due to the expected storm surge.
Cape Town weather warnings for Sunday, 7 July 2024
The SAWS has issued several weather warnings and advisories for Sunday, 7 July 2024:
- Orange Level 8 Warning for Disruptive Rain:
- Expected over the West Coast, City of Cape Town, Cape Winelands, and Overberg districts.
- Potential impacts include flooding and possible damage to roads and bridges.
- Yellow Level 2 Warning for Disruptive Rain:
- Expected over the northern West Coast, Laingsburg, eastern Garden Route, and southern Namakwa.
- Potential impacts include localized flooding and difficult driving conditions on dirt roads.
- Orange Level 6 Warning for Damaging Coastal Winds and Waves:
- Expected between Alexander Bay and Cape Agulhas, spreading to Plettenberg Bay by afternoon.
- Potential impacts include damage to coastal infrastructure.
- Orange Level 6 Warning for Damaging Interior Winds:
- Expected over the southern West Coast, Cape Winelands, and eastern Overberg districts, and the interior of the Eastern Cape.
- Potential impacts include structural damage.
- Orange Level 8 Warning for Damaging Interior Winds:
- Expected over the City of Cape Town, Drakenstein, Stellenbosch, and western Overberg municipalities.
- Potential impacts include structural damage.
Weather conditions will be cloudy, windy, and cold to very cold, with scattered to widespread showers and thundershowers over the western and southwestern parts, spreading to the eastern parts in the afternoon.
Snowfalls are expected over the western high ground in the morning, spreading to the eastern mountain peaks by evening.
What is a storm surge?
A storm surge is an abnormal rise in seawater levels above the predicted astronomical tides, generated by an intense weather system such as a storm or cyclone. This surge can be positive or negative, depending on the direction and intensity of the winds and atmospheric pressure changes.
A positive storm surge occurs when strong near-surface onshore winds push seawater toward the coast, significantly increasing water levels. This effect can be exacerbated by rapid cyclogenesis, where the central sea-level pressure deepens rapidly, typically over a period of 12 hours or more.
Storm surges are calculated as the difference between the expected astronomical tide and the actual water level, including the effects of weather.
When strong onshore winds and waves coincide with high tide or spring tide, the impact on the coastline can be severe, leading to flooding and coastal erosion. Conversely, if these conditions occur during low tide, the impacts can be minimal.
The SAWS Wave and Storm Surge (SWaSS) model predicts a significant storm surge along the west and southeast coastlines of South Africa, with the most severe conditions expected early Monday morning between 02:00 and 08:00.
Coastal areas are advised to prepare for potential impacts and take necessary precautions to protect lives and property.
