An Analytical Study of Meso-Scale Vortex-Like Disturbances Observed around Wakasa Bay Area

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Abstract
It has been reported occasionally that meso-scale vortex-like echo patterns are detected by radar observation. Three meso-scale vortex-like disturbances aligned along the coast of Wakasa Bay observed on 9 February 1968 are investigated. Structures of the disturbances, their temporal variation and the general field in which the disturbances are imbedded are analyzed using all the available data of PPI radar observation at Fukui and surface weather observation in Hokuriku and Kinki districts. The disturbances have the horizontal scale of -100km in a lower half of the troposphere. These disturbances are characterized by the cyclonic rotation with the vertical component of vorticity of 10-3-10-4s-1 and the horizontal convergence of -10-4s-1 and by the lower pressure of -1mb at the center of the disturbance than the environment at the surface. The precipitation amount of several millimeter per hour is accompanied by passage of the disturbances. The air colder as much as 1°C is found around the center of the depression in the early stage and then replaced later by warmer air at the surface. A series of the three disturbances are imbedded in a remarkable cyclonic horizontal shear zone located in the surface pressure trough in the general field.

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