Evolution of a Tropical Disturbance in the Caribbean Sea Region

Abstract

The transformation process of a wave disturbance in the Caribbean Sea region into Hurricane Alma (1962) is studied in detail based on conventional surface and upper-air data, TIROS V pictures and some research flight observations. The disturbance was cold-cored in the lower troposphere at the beginning. The vertical motion was thus negatively correlated with virtual temperature in the lower troposphere. Through an interaction between the disturbance and a pronounced upper-level shear line situated to the west, a secondary warm low was initiated at lower levels near the surface. The initial phase of upper-tropospheric warming over the low was related to the downward motion east of the upper shear line. When the secondary low developed, the cold-core wave disturbance disappeared. The precipitation area which was initially located to the east of the disturbance approached the center of the secondary low-level cyclone. The development of the low-level cyclone with a gradual warming in the upper troposphere over the rain area led to the formation of a warm-core storm with a pronounced outflow in upper levels, The change of cloud features with the development is also described.