Seasonality of westward-propagating disturbances over Southeast and south Asia originated from typhoons

We investigate the seasonal changes in the westward-propagating disturbances (WDs) in Southeast and South Asia originated from typhoons over the western North Pacific. WDs tend to move over the northern part of the Indochina Peninsula and South Asia in summer, while over the southern part of the Indochina Peninsula and the Bay of Bengal in fall. Although the number of landfall on the Indochina Peninsula is the largest in fall, the active season for WD with a more west-oriented track is identified in late summer. The seasonality is related to large-scale atmospheric conditions. The easterly region throughout the latitude band 15 degrees-25 degrees N at 700 hPa during the active phases of intraseasonal variation in monsoon trough and the large-scale trough in lower troposphere over the Bay of Bengal are favorable conditions for taking the more west-oriented track of WD in late summer. Such conditions are found neither earlier summer nor fall.