The vertical profile of ocean current needs to be characterised for preliminary engineering applications such as exploration drilling. The acquisition of suitable current profile data can be a key challenge, especially in relatively unexplored deepwater frontier regions. Recent years have seen a dramatic increase in the use of ocean current models for this purpose, frequently involving freely available data from the HYCOM consortium. These data have proven reliable in some locations, but the accuracy remains questionable, or unproven, in many others. This paper describes a study in which it was clear from the outset that HYCOM would not represent dominant features of the local current regime. This concerned the region offshore Namibia, near 30°S, at which latitude the inertial period of natural ocean oscillation equals the diurnal period of 24 hours. This region is also subjected to relatively strong diurnal sea breezes, which can drive nearly resonant inertial responses in the ocean, which can, in turn, dominate the current regime. The spatial resolution of the wind field used to drive the global HYCOM model is insufficient to resolve this critical wind forcing, so the resulting model currents cannot represent the dominant features. Fortunately some relevant measurements were well documented in the public domain, from which a pragmatic inertial current simulation methodology was developed. Lack of inertial energy was actually beneficial for using HYCOM daily spot values to represent other, longer term, components of the flow. If inertial currents had been represented in the model, then more frequent values would be required to capture them. HYCOM data proved useful for representing long term inter-annual variability in the features it does represent, including meanders in the seasonal Benguala current.

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