The predictions of the individual atmospheric models are objectively combined into a multi-model ensemble probability forecast, where weights assigned to the individual models are based on historical hindcast performance using prescribed, observed SST for the season and location. View the maps showing these purely objective forecast results, where the calendar year (2007 in above case) is flexible. The IRI's final issued climate forecasts are determined mainly by this objective multi-model product but sometimes may be adjusted slightly on the basis of factors such as known model biases, uncertainties in aspects of the SST forecast, late-breaking SST or climate information, etc. The most common kind of such subjective, human adjustment is a weakening of the forecasts' deviation from the climatological probability distribution, that distribution being equal probabilities (1/3) for each of the tercile-based categories.