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Two classes of people criticize Weather Bureau forecasts, the public and the Weather Bureau. Probably the Weather Bureau itself is the severer critic of the two. Its rules for purposes of verification are inflexibly definite. The practise is definite as to the character of the forecast, the time of occurrence, and the place of occurrence.

Rain—Fair.—By rain in this connection is meant any kind of precipitation in season. The general term precipitation is used to embrace rain, snow, sleet or hail; but in forecasts, “rain” may be used to cover any or all. To verify a “rain” forecast, precipitation must occur to the amount of 0.01 inch or more. The forecast may designate “rain,” “showers,” “thunder-storm,” “snow,” “sleet,” etc., but the meaning for verification does not vary. Even the term ”clearing,” when used in connection with a rain forecast, means that rain will fall during a part of the time covered by the forecast.

For purposes of verification, fair means only the absence of precipitation. The forecaster may differentiate the kinds of fair weather to be anticipated as partly cloudy, cloudy, unsettled, overcast, or threatening—these are all variations of the forecaster’s ”fair.” If precipitation occurs to the amount of o.oi inch or more, by the rules of the Weather Bureau the forecast fails.

Warmer—Colder.—The rules concerning temperature forecasts are also equally definite, but with certain limits in verification. If the forecast is ”warmer,” any rise of temperature is a verification; so also is ”cooler” if lower temperature is forecast. But if a change is not forecast, or if the words ”not much change,” ”slight change,” ”continued warm,” (or cool), or ”stationary temperature” are used, a definite number of degrees (6 in summer and 10 in winter) is required to vitiate the