A meteorological satellite study of a double vortex system over the western Pacific Ocean

A double vortex system consisting of Tropical Cyclone "Annie" (Southern Hemisphere) and Tropical Storm "Gilda" (Northern Hemisphere) developed over the Western Pacific Ocean during November 1967. The development and sub-sequent movement of the vortices are studied by means of meteorological satellite photographs. Estimates of maximum wind speed and central pressure for each vortex are made using a method developed in the National Environmental Satellite. Center, Washington, D. C. The sequence of events observed in the development of the vortex pair is discussed and it is suggested that Cyclone "Annie" may have developed as a result of the earlier formation of the Northern Hemisphere vortex. It is concluded that the occurrence of double vortices is more likely during the transition months. Near the equator the vertical component of vorticity due to the earth's rotation is small and the development of a vortex will depend to a large extent on the low level wind field prevailing in the vicinity of an area of large-scale low level convergence. The study provides additional evidence that meteorological satellite data are of great value in the investigation of weather systems in the data-sparse equatorial regions.