On the utility of correcting Barometric tendencies For normal diurnal variations for Forecasting in India

Abstract

Forecasting offices in India are at present preparing a chart showing 24 hour pressure change and using the same to indicate pressure tendencies for forecasting purposes. As a period of 24 hours is rather too long to give a reliable indication of pressure changes that would follow, it is considered that a chart showing pressure changes during a shorter period corrected for normal diurnal variation would give a more reliable indication of the present tendencies. It has been shown that the corrected pressure changes since the last hour of observation from the corresponding value at the previous hour. This procedure automatically takes into account the diurnal correction, which is appropriate for the individual stations and also for the season or period under observation and thereby eliminates the error, which would otherwise come in using a mean correction for the diurnal variation.

The utility of such a chart is illustrated in the case of typical weather situation during week ending 3 October 1948. The inferences that could be drawn on the basis of the corrected pressure changes for shorter period and those on 24 hour pressure changes have been compared day to day with reference to actual development of weather during the period.