Weather and Equatorial Waves Over Southeast Asia During the Summer Monsoon

Abstract

Analysis of wind, pressure and cloudiness patterns shows that the weather of Southeast Asia during the southwest monsoon relates best to westward-moving equatorial waves. These waves are basically the same as those found over the western Pacific by other investigators although they are often not perceived without special analysis as they move through the vigorous monsoonal circulation. They are characterized by average wavelength of 3100 km, average period of 5½ days or speed of 6.5 m sec−1, a deep cool center from the surface to about the 300-mb level, and a deep band of convergence and cloudiness which feeds into the center from the southwest and south. Relatively good weather with lower amounts of cloudiness and areal precipitation coverage is normally found in the area of synoptic-scale subsidence between waves.