An extreme precipitation event in Central Norway

At the end of January and beginning of February 2006, an extreme precipitation event occurred over Central Norway. The precipitation in addition to warm temperatures produced flooding and landslides that caused considerable damage to infrastructure. The event is explored with conventional data, data from remote sensing and numerical simulations. It is shown that there was very little quasi-geostrophic forcing during the event and that the extreme precipitation is locally generated by strong and persistent winds impinging the mountains. The mountains in the southwestern part of Norway, far away from the precipitation, contributed significantly to the extreme, by blocking, deflection and enhancement of the low-level flow. The warm and humid air masses involved are shown to originate in the subtropics. Assessment of forecasts with different lead times reveal a sensitivity to a baroclinic system to the east of Newfoundland upstream of the event in Central Norway.