On January 9th, 2005, the Baltic proper experienced exceptionally high waves as a deep low passed northeastward. Early wave predictions exceeded 10m, on shorter range this was reduced to about 8m. Waves recorded by the Finnish Institute for Marine Research (FIMR) at the North Baltic Proper buoy, located at 59 15N 21 00E (position indicated on Fig. 1) subsequently showed a maximum significant wave height of 7.2 meters on Jan 9th at 04-08 utc.

In Fig. 2, the observed wave height is compared with DMI-WAM wave forecasts, with short (6 hour), medium (24 hour) and long (48 hour) forecast range. The early forecasts overpredict the event, but the forecast improves as we close in.

Fig. 3 compares the maximum predicted wave height at the buoy location with the highest record during the event, for a number of forecast ranges. At ranges >42 hours, the maximum wave height was overestimated by roughly 3 meters. Getting within 30 hours of the event, the forecast was reduced to 8-8.5 meters. This corresponds to a prediction error of 12-18%.

A comprehensive study of this case has been carried out, initiated and led by Dr. Tarmo Soomere (soomere@cs.ioc.ee), Tallinn University of Technology, Estonia.

The full article has been published in Natural Hazards and Earth System Sciences:
Soomere, Behrens, Tuomi, Nielsen: Wave conditions in the Baltic Proper and in the Gulf of Finland during windstorm Gudrun

Fig. 1: Location of the Finnish North Baltic Proper buoy

Fig. 2: Observed wave height at North Baltic Proper and forecasts at short (red),
1 day (green), and 2 day (blue) range.

Fig 3: Predicted maximum wave height at North Baltic Proper, as a funtion of forecast range.

Jacob Woge - Feb. 10th 2005 (rev. Aug 7th 2008)