A Numerical Scheme for Predicting the Location of Tidally-Generated Fronts in Shallow Water.

A hydrodynamic numerical model is used to compute tidal currents and calculate the parameter log sub 10 (u to the 3rd power/h), where u is the maximum local tidal speed and h is the depth. A recent theory has shown that fronts, marking the boundary between stratified and isothermal water, can be expected to form where this parameter takes a critical value of about 2.2. Thus, if the amplitude and phase of the tidal elevations are known around a region of interest then the likely location of fronts can be predicted if the bottom topography is known. As an example of the method the scheme is applied to the Southwestern Approaches to the English Channel, and good agreement is obtained for the predicted location of a thermal front that has been observed at the western entrance during the summer months. In particular, the model shows that even eastward winds of Beaufort force 8, which occur for at least 10% of the time in this region, are unlikely to influence the location of the front. The computer program and instructions for its use are given in an appendix. (Author)