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Internet KNMI Weather R&D Storm Surges 4 Feb 2011 case






Sea level forecasts

The case of 4 February 2011

The Storm Surge Warning Service (SVSD) drew my attention to the large discrepancies between the different ensemble forecasts for the high tide in Den Helder on the evening of Friday 4 February 2011.

On February 1, the forecasts with the WAQUA/DCSM storm surge model (right, upper) predict a surge with its median on 1.5m and a probability of 10% to exceed the alarm level, but the forecasts with the WOMOD model (right, lower) do not give any significant surge. The figures on the right enlarge when you move the mouse over them.

The forecast maps (see menu right), based on the forecast of 1 Feb 00:00, suggest that the surge originates from the strong westerly winds north of Schotland the night before and travels down the British coast to the Southern North Sea. As WOMOD does not know about what happens north of Schotland, it does not pick up this surge.