A primitive equation barotropic instability study of the monsoon onset vortex.

A primitive equation barotropic stability analysis of the 700 mb zonal wind profile over the Arabian Sea was performed for each day between 10 and 14 June 1979, during the onset phase of the monsoon. The flow was found to become progessively more unstable with the passage of time. The most unstable inviscid primitive equation mode has an e-folding time of 3.1 days, a wavelength of 3500 km and a westward phase speed of 1.9 m s-1