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 forecast. Modifying words, “slightly,” “much,” “probably,” etc., do not relieve the forecaster of the failure of his verification.

Time of Occurrence.— The forecasts most generally sent out for publication are based on the 8:00 observations and reports. The terms designating time are ”to-night” and the name of the following day. “To-night” covers the twelve-hour period from 8:00 of the current day to 8:00  of the following day. Therefore, whatever is forecast for “to-night” must occur within these time limits. “Rain to-night” would fail of verification if none occurred until after 8:00 the day following, even though a heavy downpour set in immediately thereafter. “The following” day begins at 8:00 and ends at 8.00  after the current day—that is, for purposes of verifying the 8.00  forecast on Monday, “Tuesday” covers only that portion of the day between 8.00  and 8.00

Place of Occurrence.—Most forecasts are made to cover individual states. The larger states are subdivided into “north,” “south,” “east” and “west” sections. The daily forecast may be for the whole of a state or for any of its sections. If rain is forecast, say, for New Jersey, and none is reported from any of the stations in the. state, the verification fails, even though showers may have occurred at nearby stations in Pennsylvania and New York.

The Value of Safety.—Measured by their effect on commerce, production, and transportation, some weather changes are of no particular effect; they are neither beneficent nor hurtful. Other changes are classed as “critical”; if they occur unexpectedly—that is, without forewarning, they may result in loss by damage, or by destruction; they also may cause human suffering.

The “unexpected” may be unseasonable rains, snowstorms, floods, frosts, cold waves, hot spells, tornadoes, or other severe weather. These are the weather conditions to which the forecaster must be keenly alert; they are the possibilities that demand his chief care. Forecasters realize that it is wiser to warn against a killing frost that does not materialize than to fail in warning against one that does appear. The unverified forecast of frost may cause some trouble and some loss, but the killing frost that comes without warning is likely to result in loss infinitely greater.