Abstract : 3N.16
Local forecast verification in the regional bulletin “Dolomiti meteo”

Gianni Marigo, Andrea Crepaz, Anselmo Cagnati
ARPAV - Centro Valanghe di Arabba

The Avalanche Centre of Arabba in the last 25 years issued weather forecast, in a regional scale, for the venetian Dolomites and Prealps, a mountainous area about 5000 km2 large on the southern slope of the eastern Alps. Since 2005 the regional bullettin contains also an experimental section, in which a specific forecast 24h valid is made, for 8 places which are particularly representative of the venetian mountain, both for climatic and social-economical manner. Data, forecasted for the day after the issue’s day, concern the Low and the High temperatures, the cloud cover, the chance of precipitation and the cumulated value separated in rain and/or snow. A first verification of the accuracy of the local forecast has been made ex-post for the year 2005, comparing the temperatures and precipitation forecasted values with the data measured by the automatic stations’ network. Concerning the Low and the High temperatures’ values, the average deviation related to the stations are placed between 1,5°C and 2,5°C, with overall average values respectively of 1,7°C and 1,9°C. Concerning the precipitation, the deviations for the different stations resulted between 2 and 3 mm for any rainfall event, with overall average values of 2,5 mm. The results of this first verification were altogether encouraging and remarked the necessity to investigate deeper, by a forecasting point of view, the synoptic situations which brought the biggest deviations, as the nocturnal irradiation, the daily range of temperatures with low relative humidity values, the thermoconvective precipitations and the heavy rainfalls. By a further comparative analysis of the forecasted and measured data of the year 2006, it could be possible to find a confirmation of the confidence of the local forecast.