Verification is key to continued improvement of our accuracy. It involves comparing our forecasts against relevant observations to determine how accurate they are.
Verification underpins the targets set by government and the Public Weather Service Customer Group (PWSCG). These forecast accuracy targets are part of our ongoing long-term commitment to improving the accuracy of our forecasts to the public.
Forecasts for both maximum and minimum temperature are compared to the actual values observed at an agreed list of 119 sites across the UK. The sites used for verification are those where we have quality-controlled data and where we produce forecasts for.
The early morning forecast on our website is used to produce a percentage number of the times when the forecast is accurate to within +/- 2°C. This is based over a rolling 36-month period to smooth out extremes and give a representative average.
Temperature forecast - performance
This information will be updated every month.
Minimum temperature - first night of forecast
- 86.5% of minimum temperature forecasts are accurate to within +/- 2°C on the first night of the forecast period (36-month average).
Maximum temperature - first day of forecast
- 95% of maximum temperature forecasts are accurate to within +/- 2°C on the current day (36-month average).
Three-hourly temperature forecasts are monitored in the same way as maximum and minimum temperatures, but using our three-hourly forecasts for the current day.
- 95.1% of three hourly temperatures are accurate to within +/- 2°C on the current day (36-month average).
We also monitor how well we forecast weather types, e.g. 'rain' or 'sun'.
The forecast weather type is compared to the actual weather observed at the same agreed list of 45 stations across the UK. The early morning website forecast is used to produce a percentage number of the times when we correctly forecast the weather as 'rain' or 'sun'. This is based on our three-hourly forecasts for the current day and is based over a rolling 12-month period, as it is a relatively new measure.
- 0.562 Equitable Threat Score (ETS) of three hourly weather is correctly forecast as 'rain' on the current day.
- It is difficult to forecast rainfall at a pinpoint location, therefore the target for this element is not as high as for others. For example, one location may have rain and a location a mile away may remain dry.
To verify the 'rain' weather type, any hourly observations of precipitation will count towards a 'rain' observation.
The following symbols would be included in the definition of 'rain':
|light rain shower (night)||heavy rain shower (night)|
|light rain shower (day)||heavy rain shower (day)|
- 0.537 Equitable Threat Score (ETS) of three-hourly weather is correctly forecast as 'sun' on the current day.
To verify the 'sun' weather type, hourly observations of cloud cover of between 0 and 2 oktas count towards a 'sun' observation.