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Edwin Kessler III

Abstract

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James W. Wilson
and
Edwin Kessler III

Abstract

A study of radar summary maps collected from July to December 1961 shows that the echo areas reported are closely associated with precipitation and that the reported echo intensifies and heights of tops are valuable for assessing the occurrence of thunderstorms and other precipitation types. Use of past-hour motion arrows shown on the maps for prediction by translation gives better 3-, 6-, and 9-hr forecasts of echo areas over St. Louis, Mo., than does persistence. The symbols given to indicate the fractional echo coverage within echo areas are usefully related in summer to the probability that precipitation occurs at any point within the echo area. Such relationships can be combined with the probabilities associated with echo-area forecasts to obtain a probability for the future occurrence of echo at any particular point. Some means for extending such probability designations to route forecasts are briefly indicated.

A principal weakness of the present radar data observing and reporting methods is the coding scheme. The encoded echo observations are very general and the location of echoes within the areas indicated on the radar summary maps is not shown except for particularly noteworthy cases. However, the present data demonstrate both that radar is a valuable aid for terminal and enroute forecasting and that forecasts of useful accuracy and greater precision should be possible when more precise radar data become available.

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Edwin Kessler III
and
John A. Russo Jr.

Abstract

The great information-processing capacity of modern digital computers is used to assemble radar data in a form suitable for its application to weather analysis and forecasting studies and for investigation of the data's physical and statistical properties. Data are collected by PPI photography at steps of the antenna-elevation angle and radar-system sensitivity and aye reduced manually to digital form. The data are registered on magnetic tape for entry to the digital computer, wherein they are edited, range-normalized, reassembled to produce plan distributions that refer to a constant altitude above the earth, and processed for the distributions of the heights of echo bases and tops. Any of a practically limitless number of processing combinations can be selected to portray the intensity, male, and vertical development characteristic of the echoes for a particular period and location. The outputs of the computer program are printed distributions, for visual inspection and manual processing, and magnetic tapes containing the data in a form suitable for analysis by other computer routines. This program provides practical means for developing knowledge of radar data; realization of the full benefits of radar under operational conditions will require instruments which quantize the data rapidly.

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