And the weather on Table Mountain today ...
The Table Mountain Aerial Cableway operates weather permitting. A number of variables, especially wind speed and visibility, are taken into account throughout the day to determine whether the Cableway is open or closed to visitors.
Identifying the conditions on the summit that affect the Cableway's operational status is a precise skill, especially since weather and wind fluctuations could mean that the ride to the top of Table Mountain is open one hour, but closed the next.
Operations manager Mike Williams says the Cableway depends on a number of weather information channels, but this is not enough. Wind speed is determined by the Cableway’s own weather stations, which are linked to the operating plant. Williams says the weather stations provide a 24-hour weather trend, as well as wind speed measurements.
“Table Mountain weather is unique. If you call the Cape Town weather office, they will provide four different weather reports for the Cape Town area – Helderberg, Cape Point, Cape Flats and CBD – that is how different the weather can be in Cape Town. But taking a general approach can be quite accurate, as well as the fact that we have become very good at understanding the weather – we get it right most times,” Williams says.
Adverse weather conditions, including temperature, wind speed and visibility, are taken into account when deciding whether or not to suspend operations.
The strength of gale-force winds, from 45 to 90 kilometres per hour, is also a determining factor. If the wind picks up during the day and it becomes too dangerous, a loud siren is activated, a sign for visitors to make their way to the Upper Cable Station so that they can be ferried down.
The siren only sounds when a decision has been made to suspend operations. There is no set wind speed that causes the Cableway to be closed – the direction of the wind is equally important, as is the prediction. The hooter may sound before the wind arrives because there is a long queue and the manager on duty can see the wind approaching.
Williams says: “If there is expected wind we use indicators such as the amount of cloud cover over the Hottentots Holland mountains, the white horses (waves driven by the wind, resulting in broken white crests) on the Atlantic seaboard side, and the dark wind line over Table Bay. If the wind is approaching we will notice the cloud getting thicker over the Hottentots Holland mountains, the white horses will get closer towards Camps Bay, and the dark wind line will move closer to Robben Island.”
When the orographic clouds that form the iconic tablecloth cover the mountain, it does not mean the Cableway has suspended operations. Orographic clouds are formed when a mass of air is forced from low ground to increasing high ground. As the mass rises, it cools down and forms a cloud.
Wikipedia says specifically to Table Mountain, orographic lift happens when “the cold Atlantic air mass flows up over the north-western face of the mountain to 3 500 feet above sea level and is met by the warm Indian Ocean air mass from the south-eastern back side of the mountain, forming the famous tablecloth”.
Weather conditions on Table Mountain are updated on the website’s homepage, Facebook page and Twitter feed, throughout the day. One of the reasons for the weather updates is that if the weather in the city is cloudy and wet, the same conditions may not prevail on the mountain; Cape Town locals live by the adage that you can easily experience four seasons in one day.
And even though geographically-speaking the mountain is part of Cape Town, the temperature at the top is six degrees lower than in the rest of the city.
Many people love the idea of “walking in a cloud” or being on top of the world, and low-hanging clouds often do not affect operational states. The clouds mass mid-way up the mountain, and from the city it appears that the mountain has “disappeared” behind the cloud. But on top of the mountain the sky is blue, and the views of a city shrouded in cloud a magical experience.