Summary:

In the paper the verification of precipitation condition forecasts are presented. The forecasts have been developed in the monitoring system of water deficiency and excess conducted by the Institute of Technology and Life Sciences. Analyses were performed for seven meteorological stations within Kujawy Region, south-eastern part of Pomerania and western Wielkopolska in the months of the growing season (April-September) in 2013-2014. Actual precipitation deficit and surplus and their 10-day and 20-day forecasts were determined every 10/11 days for the period of 30/31 days using the standardized precipitation index SPI. Two verification criteria were adopted: the difference between actual and predicted SPI cannot be greater than 0.5 and the agreement of the precipitation category classes. The verifiability is determined as the relative frequency of the forecasts meeting these criteria. It was found that the average verifiability of 10-day forecasts in the study area was high and equal to 80% for the assumed criteria. In the case of 20-day forecasts average verifiability was respectively 52%.