Description

The probability of precipitation type is displayed combined with the instantaneous total precipitation rate (another IFS variable) to provide for example an indication of potential freezing rain events and their likely severity, heavy snowfalls, etc. In this aspect, each precipitation type is also divided in 3 different categories depending on the precipitation rate, from one minimum value to 0.2 mm/h (low intensity), from 0.2 to 1 mm/h (medium intensity) and greater to 1 mm/h (high intensity).

To define the minimum precipitation rate for each precipitation type to classify dry from precipitating, we use a daily basis verification tool that compare present weather from SYNOP observations and for each type of precipitation the frequency bias is enforced to 1 (the same number of real events than forecasted events). Six values of precipitation rate threshold are applied in order to calculate the bias for each precipitation type: 0.02, 0.05, 0.07, 0.1 and 0.12 mm/h. According to this technique, the minimum precipitation rate threshold applied for each precipitation type is: rain>0.12 mm/h, sleet>0.1 mm/h and all other types>0.05 mm/h.