Waterspouts over the North and Baltic Seas: Observations and climatology, prediction and reporting

Abstract

On 25 August 2005, three waterspouts were observed close to the research platform FINO1, 45 km off the German North Sea coast and situated in a prospected large offshore wind park area. We analyse this case in relation to the synoptic setting of a waterspout day over the Baltic Sea and compare it to the waterspout climatology of the German Bight and the western and south-western parts of the Baltic Sea. The waterspout hazard to offshore wind parks is assessed as about 1 waterspout per year and per 10 000 km 2 . So, should current scenarios for future wind park development materialise, their large total area may experience a waterspout every other year. The prediction of such events is investigated in view of concepts recently proposed for Mediterranean and western North Sea waterspout forecasting. Reporting issues influencing the climatology encompass both a weekend low in reported events, as well as a bias toward ship routes and main SYNOP times in ship reports. The latter may be mitigated by more reports from yachtsmen.