Study of a heavy rain vortex formed over the eastern flank of the Tibetan Plateau

A case of the heavy rain vortex which occurred during the period 14-15 July 1979 is studied using a limited-area mesoscale numerical model. This is a representative example of a group of warm southwest vortices that often form over the eastern flank of the Tibetan Plateau after the onset of the summer Indian monsoon. The developing vortex is noticeably detached from the polar frontal zone. a 180 degrees phase shift exists between the upper and lower layer vorticity fields. In the boundary layer, a pronounced northward transport of mass and moisture is connected with an intense upward motion near and to the E of the 700-mb vortex center, while the southward cold advection is insignificant. Without latent heating, dynamic instability and/or forcing of the large-scale flow interacting with the Tibetan Plateau is not sufficient to generate the observed disturbance. Our principle result is that the warm heavy rain vortex in this case study is triggered by a migratory plateau boundary layer disturbance and basically driven by cumulus convective heating. -from Authors