The relationship of extreme precipitation events to weather conditions in Nordland,Norway

We examined the distribution of extreme daily precipitation events (100?mm or more per day) in relation to weather conditions in the county of Nordland, Norway. Precipitation data included 88 weather stations and cover the period January 1964–March 2002. Over this period, extreme precipitation took two forms: frontal precipitation (associated with a warm or cold front) and warm sector precipitation (associated with the air masses between two fronts). Our analyses show that 57% of the extreme daily precipitation situations were classified as warm sector precipitation. This stands in contrast to claims that significant warm sector precipitation will very rarely, if ever, propagate as far north as Nordland. Because extreme precipitation may be linked to the risk of avalanches, earthflows and mudflows, it may be important to re-evaluate the forecasting criteria for heavy rain in north Norway.