MONSOONAL MID-TROPOSPHERIC CYCLOGENESIS.

Abstract

The essential elements of a representative flow over the northeastern Arabia Sea and central western India are incorporated into a modified Eady model in which the basic flow is assumed to have a zonal component with a uniform easterly shear, and a southerly component vanishing at the surface and in the upper troposphere but having a maximum value at a low tropospheric level. The instability analysis indicates that with plausible values for the parameeters, the horizontal length scale, the growth rate and the phase speed of the most unstable mode are quite comparable to the corresponding observed values. The derived properties are strikingly similar to the observed counterparts, thereby lending support to the basic hypothesis on the origin of the mid-tropospheric cyclone. The relative roles of the zonal and meridional components of the basic flow are also examined.