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Isadore Enger

Abstract

The means of daily maximum temperatures using twenty years of record are obtained. The average of these means over n consecutive calendar days is used as a predictor of the daily maximum temperature one and more years in advance. Data from ten stations in the United States for the period 1905 to 1957 are analyzed in this fashion and a series of predictions made for several values of n. If singularities are sufficiently large and persistent, then the averages over only a few days (small n) should be better predictors than averages over a larger number of days. It is found that the prediction errors decrease with increasing n and it is concluded that, whenever averages are used to estimate daily temperature values far in advance, any singularities, even if they exist at all, are much too small to be useful.

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Glenn W. Brier
and
Isadore Enger

Abstract

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Glenn W. Brier
and
Isadore Enger
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Joseph G. Bryan
and
Isadore Enger

Abstract

Whereas categorical forecasts designate a specific category of weather as the predicted future condition, probability forecasts express the uncertainty attending a forecast by giving estimates of the probability of occurrence of each possible weather category at a given time in the future. To compare the accuracy of the two types of forecast, a probability forecast can be converted into a categorical forecast by a procedure of optimization with reference to any prescribed criterion, for example, a loss function. In this paper optimization procedures are derived for converting probability forecasts to categorical forecasts when the precribed criterion is any one of three commonly used skill scores: Heidke, Vernon and Appleman. Probability forecasts of ceiling and visibility are used as examples.

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John A. Russo Jr.
,
Isadore Enger
, and
Edna L. Sorenson

Abstract

The screening-multiple-regression technique is applied to predicting surface u- and v-wind components at Idlewild International Airport for periods of 2, 3, 5 and 7 hr. The predictors are variables from 11 synoptic stations, easily obtained or derivable from conventional service A teletype data. Additional predictors are used to account for diurnal and seasonal variations. In all, 141 predictors are screened and one prediction equation is obtained for each predictand. Each equation is applicable to any hour of the day and any day of the year.

The regression equations derived from a dependent sample selected randomly from 7 years of data proved significantly better at the 1-per cent level than both persistence and climatology for the 3-, 5- and 7-hr forecasts and at the 5 per cent level for the 2-hr forecasts when tested on 1387 independent cases. The screening-regression root-mean-square errors on this independent set ranged from 3.36 kt to 4.48 kt for the u-wind forecasts and from 3.69 kt to 5.57 kt for the v-wind forecasts.

Operational 3-, 5- and 7-hr surface-wind forecasts extracted from terminal forecasts made at Idlewild are compared both quantitatively and categorically with corresponding regression forecasts made on a new set of independent data. The screening-regression forecast errors are approximately ⅓ smaller than the subjective errors, and the improvements for all the predictands are statistically significant beyond the 1 per cent level. The categorical comparison concerning only categories of <10 kt and ≥10 kt (dictated by the format of the subjective data) resulted in Heidke skill scores of 0.399 for screening regression and 0.249 for the subjective forecasts when applied to 7-hr prediction of the surface-wind speed at Idlewild.

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William H. Klein
,
Billy M. Lewis
, and
Isadore Enger

Abstract

A statistical screening procedure is used to derive linear multiple-regression equations which express 5-day mean surface temperature as a function of 5-day mean 700-mb heights centered 2 days earlier. Application of these equations to heights obtained from barotropic prognoses would have produced temperature predictions of positive skill during the test winter of 1957–58.

The forecasts can be considerably improved by including as a predictor the local value of 5-day mean surface temperature for a period 4 days earlier than the forecast period. When this term was combined with the barotropically-estimated heights, objective temperature predictions comparable in accuracy to conventional forecasts were made by multiple-regression equations. Further work is in progress to obtain additional improvement by screening the entire field of surface temperature.

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