Altimeters helped monitoring the model quality near French coasts, two of the wave height buoys being off these days. Envisat measured significant wave heights between 13 and 15 m on Sunday December 9. Significant wave height is a variable used in marine meteorology, that matches the mean height of the third of the highest waves. However, a wave over a hundred reaches one and a half this value, and some can even reach twice this. Heights once at the coast are difficult to predict, since they depend on submarine reliefs.

The wave heights measured during this storm could be the highest ever by buoys, and are certainly up to some huricanes. West of Ireland, three British meteorological buoys measured wave height over 16.5 m, with a maximum at 18.3 m on December 8 at 21 h. These heights are equivalent to those measured at the heart of hurricanes: 16.9 m for Katrina in August 2005, 17.1 m for Hurricane Luis in September 1995, or 17.9 m for Ivan in September 2004.