A method of approach to objective fog forecasting, based on the use of probability charts is suggested. Given two parameters, say wind speed and dew-point depression, at sunset as ordinate and abscissa of a chart, occurrences and non-occurrences of fog following sunset are plotted as functions of these parameters. Isolines of relative frequency are drawn, giving a probability chart. Two more such charts, using four additional parameters, are constructed, and a total probability of fog occurrence following sunset is computed as a linear function of the three individual probabilities. This result is used as a criterion for the forecast. Time of formation equations are developed, to be applied in the event a fog proves to be likely.

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* Adapted from a Master's thesis completed at New York University, 1948.