A study into the forecasting of winter precipitation from the 500-mb level.
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Authors
Powell, John H.
Subjects
Advisors
Date of Issue
1957
Date
Publisher
Monterey, CA; Naval Postgraduate School
Language
Abstract
The relatively greater accuracy of prognostic 5>00-mb charts as compared to prognostic surface charts has led to various studies attempting to forecast surface parameters from the 500-mb level. Most of these studies have been localized studies, whereas the purpose of this study was to determine the feasibility of developing a general method for forecasting winter precipitation from parameters observed or measured at the 5>00-mb level. The first approach to the problem was a statistical study of the percentages of the stations reporting precipitation in four zones of the short wave in each of four similar zones of the long wave. The four zones in each wave pattern were separated by the trough, ridge, and the inflection points of the wave. The percentages for the 16 zones defined above were plotted versus the contour gradient across the zones, the temperature gradient across the zones, and the steepness of the long-wave pattern. The scatter of these diagrams indicated that there was little or no correlation between these parameters and the percentages of precipitation in the zones. In the second phase of this study, four graphical techniques were used: the direction of the wind, 2i|.-hour height change patterns, the deviation of the height from the normal, and the advection of geostrophic relative vorticity. The results of these methods could be used to varying degrees of accuracy to forecast precipitation. Further study may improve the accuracy of these methods. The advection of geostrophic relative vorticity technique is the most promising one. The writer wishes to express his appreciation for the assistance. and encouragement given him by Professor George J. Haltiner, Professor A. Boyd Mewborn, and Assistant Professor Robert J. Renard, of the U. S. Naval Postgraduate School, in this investigation.
Type
Thesis
Description
Series/Report No
Department
Aerology