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A global deterministic wave prediction system (GDWPS) is used to improve regional forecasts of waves off the Canadian coastline and help support the practice of safe marine activities in Canadian waters. The wave model has a grid spacing of ¼° with spectral resolution of 36 frequency bins and 36 directional bins. The wave model is driven with hourly 10-m winds generated by the operational global atmospheric prediction system. Ice conditions are updated every three hours using the ice concentration forecasts generated by the Global Ice–Ocean Prediction System. Wave forecasts are evaluated over two periods from 15 August to 31 October 2014 and from 15 December 2014 to 28 February 2015, as well as over select cases during the fall of 2012. The global system is shown to improve wave forecast skill over regions where forecasts were previously produced using limited-area models only. The usefulness of a global expansion is demonstrated for large swell events affecting the northeast Pacific. The first validation of a Canadian operational wave forecast system in the Arctic is presented. Improvements in the representation of forecast wave fields associated with tropical cyclones are also demonstrated. Finally, the GDWPS is shown to result in gains of at least 12 h of lead time.

Integration techniques such as the explicit leapfrog scheme or the semi-implicit method carry out their calculations over three time levels. Because of this characteristic, these algorithms can produce computational modes that appear as superimposed onto the physical solution of the meteorological equations. These computational modes can cause problems and in order to avoid these problems or remove them, a common practice is to use a rime filter. The rime filter that is frequently used for this purpose efficiently damps the computational mode while it has little effect on the physical solution. This filter does not always behave exactly as expected and in some cases, strange results are observed. A series of simple numerical experiments are carried out in order to show that the filter can display an anomalous behaviour under certain conditions. An attempt is made to explain this behaviour by numerical analysis. This analysis gives some information as to how to avoid this anomalous behaviour in at...