Interaction of Tropical Cyclones with a Dipole Vortex

Abstract

The purpose of this chapter is to discuss certain disturbances around the pole of a Venus-type planet that result as a response to barotropic instability processes in a zonal flow. We discuss a linear instability of normal modes in a zonal flow through the barotropic vorticity equations (BVEs). By using a simple idealization of a zonal flow, the instability is employed on measurements of the upper atmosphere of Venus. In 1998, the tropical cyclone Mitch gave way to the observational study of a dipole vortex. This dipole vortex might have helped to intensify the cyclone and moved it towards the SW. In order to examine this process of interaction, the nonlinear BVE was integrated in time applied to the 800-200 hPa average layer in the previous moment when it moved towards the SW. The 2-day integrations carried out with the model showed that the geometric structure of the solution can be calculated to a good approximation. The solution HLC moves very fast westwards as observed. On October 27, the HLA headed north-eastward and then became quasi-stationary. It was also observed that HLA and HLC as a coupled system rotates in the clockwise direction.

Connections in the development of tropical cyclone Mitch (1998): A tribute to the human loss in this calamity

“…The initiation of the tropical wave at low levels could be associated with disturbances at high levels of the most unstable normal mode. The present work provides an observational study of a dipolar vortex in the upper troposphere associated with tropical cyclone Mitch; these dipolar vortices have not been documented in the literature (Pérez-García et al, 2017). Tropical cyclone Mitch was not an isolated solitary vortex but it was pushed by a directional flow generated within a dipolar vortex of the upper troposphere.…”

“…The intense warming of the warm pool of the eastern Pacific, the warm pool of the Caribbean, the Sierra Madre Occidental and the deserts of Chihuahua and Sonora cause the air to rise, which in turn generates a low surface pressure (centered near the coast NW-SW of Mexico and Central America), named as the maritime-continental thermal low (Pérez-García et al, 2017). Therefore, large horizontal convergences are generated at lower levels between the eastern Pacific about 100º W and the eastern Caribbean about 70º W. Figure 3c shows the convergent/divergent average wind and its corresponding potential function in the 925-1000 hPa layer and the average relative humidity (gray shades) in the 700-925 hPa layer for October 18, at 00 UTC.…”

“…The center of the high divergence zone associated with the dipolar vortex (200-300 hPa) was located on the southwest of the Caribbean Sea on October 25 (not shown). Mitch continued to strengthen and its central pressure reached a minimum of 905 hPa some 40 miles southeast of Swan Island on the afternoon of October 26 (Guiney and Lawrence, 1999;Pérez-García et al, 2017).…”

“…Our challenge is to understand in how many ways the environment interacted with Mitch. The dipolar vortex could have helped to intensify the cyclone and move it towards the SW (Pérez-García et al, 2017). This environment is the dipolar vortex of the upper troposphere on a large scale and can be analytically represented by a Gill solution (Gill, 1980) or an exact solution of the non-linear BVE.…”

“…(1) was integrated numerically over time in the non-linear form using the spectral transform technique, as in Pérez-García and Skiba (1999) and Pérez-García et al (2017). The basic flows used in this study are shown in Figure 6a.…”