ANALYSIS AND REGIONALIZATION OF THE DIURNAL DISTRIBUTION OF TORNADOES IN THE UNITED STATES

RICHARD H. SKAGGS Department of Geography, University of Minnesota, Minneapolis, Minn.

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Abstract

The central and eastern United States is divided into 157 overlapping square cells. Within each cell, the tornadoes that occurred from 1916 to 1964 are summed in 1-hr increments. The resulting histograms are subjected to harmonic analysis. The spatial distributions of the reduction of variance and phase angles of the harmonic components suggest substantial variation in the diurnal distribution of tornadoes. However, only two groups can be definitely isolated.

The Fourier representations of the histograms are classified numerically. From this analysis, three main diurnal distribution types and eight subtypes emerge. A preliminary attempt to account for these diurnal distributions is made; however, the degree of success is not notable and much work remains to be done.

Abstract

The central and eastern United States is divided into 157 overlapping square cells. Within each cell, the tornadoes that occurred from 1916 to 1964 are summed in 1-hr increments. The resulting histograms are subjected to harmonic analysis. The spatial distributions of the reduction of variance and phase angles of the harmonic components suggest substantial variation in the diurnal distribution of tornadoes. However, only two groups can be definitely isolated.

The Fourier representations of the histograms are classified numerically. From this analysis, three main diurnal distribution types and eight subtypes emerge. A preliminary attempt to account for these diurnal distributions is made; however, the degree of success is not notable and much work remains to be done.

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