Ensemble forecast for Plymouth

The probability forecast uses data from the Global Ensemble Forecast System (GEFS). The GEFS is basically the GFS model run an additional 20 times using slightly different starting conditions to account for uncertainty.

Tight clustering of the runs suggests a higher degree of confidence. A wide spread indicates a range of possible weather outcomes.

850hPa temperatures (°C), rainfall (mm) and snow row

850hPa temperatures, precipitation and the snow row

The upper plot shows forecast 850hPa temperatures which are approximately 1500m above sea level. They provide a way of checking how cold or warm the air mass is and aren't subject to diurnal (day to night) variation.

The lower plot shows forecast precipitation. The snow row displays the number of GEFS runs forecasting snow. This ranges from 0 to 23.