THE USE OF SURFACE PRESSURE AND TEMPERATURE OBSERVATIONS IN UPPER-AIR ANALYSIS

Abstract

A deepening Low in Texas on November 24, 1952 is selected as a case for studying the more complete use of surface pressures and temperatures in upper-air analysis. To supplement the 2100 CST sea level pressure data, significant pressures taken from station barograms for several hours preceding 2100 CST are corrected for diurnal variation, reduced to sea level, and plotted at appropriate points along lines parallel to the direction of movement of the Low. These additional pressures make it possible to show the steep pressure gradient which caused the rapid pressure rise registered on some of the station barograms. By means of synthetic virtual temperature soundings, additional heights are obtained for the 900- and 800-mb. charts at points where surface data are available and at the same points where barogram data are used on the sea level map. These additional data make it possible to show the steep geopotential gradient at upper levels corresponding to the steep pressure gradient at sea level. Geostrophic winds of 1000 knots or more are indicated by the steep gradient aloft but, by use of the equations of motion, it is found that the air does not remain under the influence of the steep gradient long enough to attain such speeds.