Numerical Sea Level Forecasts
Forecasts for storm surges at the coast of the Netherlands are made in close cooperation
between Rijkswaterstaat, Deltares and KNMI, with the use of state-of-the art numerical
models for the atmosphere and the sea.
The Dutch Continental Shelf Model is being used for day-to-day sea level forecasts by KNMI
and Rijkswaterstaat since 1990.
The model calculates the sea level and the depth averaged current on the Northwest European
Continental Shelf using wind and pressure forecasts from KNMI's limited area model HIRLAM
or ECMWF's global IFS. The current operational version, WAQUA-in-Simona/DCSMv6, uses a grid
with cells of approximately 1600m×1600m. The previous version, DCSMv5, or DCSM98,
has a grid size of 8km×8km. Until September 1999 the CSM-16 model was used with a
resolution of 16km×16km.
Deterministic sea level forecasts are produced by Rijkswaterstaat with DCSMv6 4 times per
day for 48 hours ahead, closely following the available meteorological input. A Kalman
filter is used for real-time data assimilation of sea level observations.
Real-time assimilation of observed sea levels along the British and Dutch coasts gives a
significant contribution to the high accuracy which is especially required for the management
of the storm surge barriers in the Oosterschelde and the Rotterdam Waterway (Maeslantkering).
Unlike in atmospheric modelling, however, it is not a vital part of sea level forecasting.
Probability forecasts for sea level are produced by KNMI with DCSMv5 2 times per day for
48 – 240 h ahead with forecasts from the ECMWF Ensemble.
The ensemble of sea level forecasts is transformed into probability forecasts
for high and low tides with a calibration which has been derived from model results in
Hans de Vries,
October 27, 2016