What does the weather report’s rain forecast mean?

Date:8 August 2017 Author: Nikky Knijf Tags:,

You look at your weather app every day, but do you know what that 80 per cent rain forecast means? Will it bucket down or, like yesterday, will you only get a light drizzle?

Local rain forecast

The South African Weather Service says a forecast simply “gives an indication of what weather conditions could be expected”. To achieve this they use data from two forecasting systems to help determine what local weather will do.

The first system is the Ensemble Prediction System. It system compiles a set or ensemble of forecasts to give a range of future atmospheric states. The second system uses statistical forecasting to predict atmospheric states. Using these systems meteorologists make forecasts guided by a set of standards for global predictions.

Forecasting by the numbers

So how do they turn all this data into a percentage? Well, in this video the YouTube channel SciShow looks at how a rain forecast is calculated. Check it out.


Video credit: SciShow

Image credit: freddie marriage on Unsplash