Probability of a wet day following a dry day in the month
The probability is calculated as
Pi(W⁄D)=daysdry,idaysW⁄D,i
where Pi(W⁄D) is the probability of a wet day following a dry day in month i, daysW⁄D,i is the number of times a wet day followed a dry day in month i for the entire period of record, and daysdry,i is the number of dry days in month i during the entire period of record. A dry day is a day with 0 mm of precipitation. A wet day is a day with > 0 mm precipitation.