One of SA’s most popular weather apps is getting temperatures wrong by up to 14 degrees
- Millions of South Africans rely on foreign weather apps and websites; more than three million use the Norwegian government's yr.no alone.
- That app is simple, intuitive, and user-friendly - but according to tracking done in February, it can be largely inaccurate when it comes to South Africa.
- In fact, none of the fancy weather apps were as accurate as the good old South African Weather Service.
- For more stories visit Business Insider South Africa.
Millions of South Africans rely on international weather apps and websites to help predict upcoming conditions. In recent years, more than three million have turned to the Norwegian government-owned yr.no alone.
That app is simple, intuitive, and user-friendly. It also shares forecasts with surprisingly comprehensive details, like wind speed and direction, and rain down to the millimetre, for all big cities and dozens of small towns, like Calitzdorp and Brandvlei.
It is also often wrong – especially over the longer term.
Business Insider South Africa tracked the Yr forecast highs for Cape Town for a week in February, and compared it with predictions from competing products, and actual recorded highs. yr.no was largely inaccurate, and on some days predicted temperatures were so far off, they may have had users packing light sweaters for days that were actually pushing more than 30 degrees.
Other popular apps did not fare much better – and none were as accurate as the South African Weather Service.
Here’s what we found when we compared popular weather apps to the actual weather.
For three consecutive days in February, Cape Town experienced weather in the high 20s and low 30s – but yr.no repeatedly predicted maximum temperatures between just 18 and 21 degrees, even with less than 24 hours to go.
Over a period of four days in February, yr.no predicted an average maximum high of just 19 degrees, versus the recorded average high of 28.58. (The Norwegians would have done better to just go with the average temperatures for that time of year, which is about 26.5 degrees.)
Unsurprisingly, its competitor’s didn’t get the predictions exactly right, either, though they fared better.
The Weather Channel, which delivers forecasts to many cellphones in South Africa, predicted an average of 23.3 degrees against the recorded average of 28.58 degrees.
Accuweather, which claims “superior accuracy” over other forecasting services, came in at 25.5 degrees, a not-bad 3.08 degrees below the actual temperatures.
But easily the most accurate was the South African Weather Service, which was out by just .58 degrees over the same period.
The discrepancy is perhaps not surprising considering that most international services don’t make use of on-the-ground forecasting. WeatherSA may have a barebones website and no mobile application, but it draws off locally-collected data.
Most services use international calculation models, or often in the cases of the US-based services, repackaged United States National Weather Service data, to predict weather around the world. And they then rely on presenting this in attractive, user-friendly apps, and distribution deals with major providers like Apple and Google.
According to a spokesperson at yr.no, the website and app use the European Centre for Medium-Range Weather Forecasts (ECMWF) calculation model that “has a rather coarse resolution, and that is probably why users experience discrepancies in some weather situations.”
“[ECMWF] is being ranked as the top global calculation model for weather forecasts by various international verification services, and its resolution matches similar global models,” they said. “But – like all weather computing models – it has its weaknesses and limitations. These weaknesses and limitations are both dependent on weather situations and where in the world they occur.”
By contrast, the SA Weather Service uses data from 231 automatic weather stations, 14 meteorological radar systems, weather buoys and temperature sensors scattered across two oceans, and many other specialist installations that track everything from lightning to UV exposure.
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