The heavy rain of up to 100 millimetres in parts of Pietermaritzburg on February 12 followed by flooding of some roads and buildings, turned my mind to weather warnings.
The South African Weather Service (Saws) is responsible for distributing warnings of severe weather, such as tropical cyclones, flooding rains, severe thunderstorms, snow and forest fires.
The improvements of satellite and radar coverage, as well as better computer models, have made it possible to pinpoint dangerous weather with greater accuracy.
The impact of tropical storm damage in the U.S. and in Bangladesh provide examples. A century ago large hurricanes killed hundreds of people along the east coast of America.
Today, although the destruction of property remains enormous, deaths have been cut to a few dozen in all but the largest hurricanes.
The World Meteorological Organisation, working under the
auspices of the United Nations, is determined to improve forecasts of severe weather worldwide by helping poorer countries obtain necessary equipment and skills.
The result has been a dramatic decrease in the number of people lost, compared with some 30 years ago, when tropical cyclones sweep into a country such as Bangladesh.
Another important component of weather warnings is the need for a plan of action. In the U.S. those living in the vicinity of “tornado alley”, have a safe place prepared and a planned route to reach safety in the event of a warning. When tornados are sighted they know immediately what to do to avoid injury or death.
Likewise, when a hurricane is forecast to hit the coast, the disaster management organisations have an evacuation plan on hand and most people are able to leave the area before the hurricane-force winds and ferocious rains make any escape impossible.
Our own forest fire warning system is an example of an excellent planned approach.
During the dry fire season, forecasts of expected temperature, humidity and wind strength are provided to the several fire prevention organisations, some 24 to 48 hours in advance.
This information is used to calculate a fire danger category — presented as a colour code: green is safe; blue is some danger; orange is high danger and red is extreme danger.
Once the colour for the next 24 hours is transmitted to the many forest estates, the pre-arranged work schedule for that category is implemented. If a red category is forecast, almost all normal forestry work is curtailed and staff are placed on stand-by for reacting to fire outbreaks. With people knowing in advance what to do, most fires are extinguished before they become uncontrollable.
Of course not all severe weather warnings can be so well packaged — thunderstorms, for instance. Although general warnings are given, it is impossible to pinpoint where a severe storm will develop. Also, I’ve never been sure what plan of action one can have in place for a warning of hail. Parking your car under cover is good, but what if you are out on the road?
Nevertheless, it is as well to be aware of such warnings, especially for those involved in open air activities. For those whose business may rely on avoiding severe weather, personal warnings — via sms — can be arranged with Saws.
For example, most toll road operators are warned of imminent severe weather so road patrols can be increased. Snow on Van Reenen’s pass causes traffic back-ups. Early diversions of cars to other routes avoids some of the worst traffic jams when travellers can suffer hugely from being trapped in the cold.
It goes without saying that the success of these services relies on the network functioning properly: the forecasters, satellites, radar, communications and personnel operating the planned response. If any of these fail, the protective service is weakened. The heavy rain in Pietermaritzburg is a case in point.
Although scattered thunderstorms had been forecast, there was no specific warning of the heavy falls. Part of the “watching” network was missing.
The radar based in Durban had malfunctioned and the duty forecaster was unable to identify the build-up of heavy rains and was therefore unable to warn any of those living in the areas that were flooded.
• Mike Laing is a weather consultant. Rainfall data is supplied by the SA Weather Service (www.weathersa.co.za). • Readers can send their questions on weather to weather@witness.co.za
