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<br />Fig. 1-10: SOUTHWEST MONSOON (June-August) <br /> <br />o The "rainy season." <br /> <br />o Southwest flow from the Indian Ocean brings mc)ist, convectively <br />unstable air over all of southeast Asia. The low-level westerlies are <br />deep and convergent while the upper easterlies are divergent, pro- <br />ducing extensive areas of convective activity and convective <br />precipitation. <br /> <br />o Although cloudiness and rainfall increase during the mature periods of <br />the southwest monsoon, there is a general decrease in the number of <br />thunderstorm days due to increased shear with height between the low- <br />level westerlies and the strong upper-level easterlies. <br /> <br />o Relative minima in the rainfall patterns are observed in the lee of <br />major mountains. <br /> <br />o Rainfall and convective activity can occasionally be enhanced by tro- <br />pical disturbances. <br /> <br />~ <br /> <br />Fig. I-IE: WINTER INTERMONSOONAL PERIOD (September-October) <br /> <br />o Southwest flow begins to weaken while the general instability of the <br />atmosphere is maintained. <br /> <br />o Reduction in vertical shear permits deeper convection as the ITCZ moves <br />south across Thailand. <br /> <br />o The low-level winds are weaker and more variable in direction causing <br />"rain shadow" effects in the lee of mountains to be minimized. <br /> <br />o Typhoons and tropical storms or depressions migrate into Thailand <br />bringing heavy rains to coastal areas. <br /> <br />r <br /> <br /><! <br /> <br />~ <br /> <br />6 <br />