The Ocean Forecasts for the St. Lawrence Gulf and Estuary are issued by the personnel of the Modelling and Operational Oceanography section of the Canadian Hydrographic Service (CHS), Maurice Lamontagne Institute, Fisheries and Oceans Canada.

The surface currents and sea ice forecasts for the Gulf of St. Lawrence are extracted from a three-dimensional numerical model computing the oceanic circulation under the influence of tides, the St. Lawrence River fresh water runoff, the atmospheric forcing, and the sea ice drift, growth and melt. The model has been validated under a series of scientific and operational research and development programs within the Department of Fisheries and Oceans Canada. The validation process was done against a number of oceanographic observations including currents, water level, water temperature and salinity, and sea ice drift, concentration, and thickness.

The physical data used as input to the model are:

• Tidal elevation at Cabot and Belle-Isle straits;
• Forecasts of fresh water run-off at Quebec City;
• Meteorological forecasts issued from the GEM model of the Canadian Meteorological Centre, Meteorological Service of Canada, which includes wind, air temperature, cloud cover, and relative humidity;
• Ice observation integrated in daily charts from the Canadian Ice Service, Environment Canada.