Analysis of Hurricane Catarina (2004)

Abstract

The development of Hurricane Catarina over the western South Atlantic Ocean in March 2004 marks the first time that the existence of a hurricane has been confirmed by analysis and satellite imagery in the South Atlantic basin. The storm undergoes a complex life cycle, beginning as an extratropical precursor that moves east-southeastward off the Brazilian coast and toward the midlatitudes. Its eastward progress is halted and the system is steered back westward toward the Brazilian coast as it encounters a strengthening dipole-blocking structure east of the South American continent. Entering the large region of weak vertical shear that characterizes this blocking pattern, Catarina begins a tropical transition process over anomalously cool 25°C ocean waters above which an elevated potential intensity is supported by the cold upper-level air associated with the trough component of the block. As the convective outflow from the developing tropical system reinforces the ridge component of the dipole block, the storm is accelerated westward toward the Santa Catarina province of Brazil and makes landfall there as a nominal category-1 hurricane, causing extensive damage with its heavy rains and strong winds. The complex evolution of the system is analyzed using a suite of diagnostic tools, and a conceptual model of the tropical transition and steering processes in the presence of a dipole block is developed. Once the essential properties of the upper-level flow are established, an analog study is undertaken to investigate lower-atmospheric responses to similar blocking regimes. Persistent dipole-blocking structures are found to be rare east of South America; however, the evolution of systems occurring during these periods is shown to be complex and to exhibit various subtropical development modes.

Spatial distribution of water erosion risk in a watershed with eucalyptus and Atlantic Forest

“…It should be mentioned that this monthly value was greater than the annual values for the other six years (Figure 2). This can be justified because a hurricane, the first in modern times, in the South Atlantic Ocean struck the Brazilian coast in this month (LE COMTE, 2005;MCTAGGART-COWAN et al, 2006). Although this hurricane has hit mainly the Santa Catarina state coast, it caused heavy rainfall events with high intensity in a large area of the Brazilian coast, including Espírito Santo state.…”

Upper-tropospheric environment–tropical cyclone interactions over the western North Pacific: A statistical study

“…5f and g shown here, in which the anticyclone to the northeast of the TC center develops intensively so that it is gradually cut off from the westerlies and forms a cutoff blocking. Such a blocking flow pattern, as noted by McTaggart-Cowan et al (2006), would facilitate a midlatitude vortex precursor transiting into a TC (known as tropical transition), whereas the similar flow pattern in Fig. 5g is likely to facilitate the transition of a TC into an EC (known as extratropical transition), depending on the accompanying VWS and underlying SST.…”

“…5h, but TCs are already inside the westerly jet core with large VWS, which is different from the picture of Holland and Merrill (1984). Another example was given by McTaggart-Cowan et al (2006), who presented a conceptual model of tropical transition in a dipole-blocking environment (see the right-hand column of their Fig. 2).…”

Estudo de caso de uma situação atmosférica entre 12 e 19 de setembro de 2008, com algumas características semelhantes ao evento Catarina

“…O bloqueio tipo "omega" consiste do domínio de uma alta pressão em 500 hPa e o tipo dipolo de uma baixa desprendida do escoamento de oeste com núcleo frio nas latitudes mais baixas, que se encontra meridionalmente em fase com um anticiclone de núcleo quente nas latitudes mais altas. O bloqueio dipolo, além de produzir a quebra do jato zonal e criar fortes correntes em direção ao equador, também pode gerar escoamento anômalo de leste em níveis médios e altos, devido à inversão do gradiente meridional de temperatura e altura (ciclone com centro frio em latitudes baixas e anticiclone com centro quente em latitudes altas), que pode influenciar os sistemas em superfície (McTaggart-Cowan et al, 2006). Para a identificação de bloqueios são utilizados índices que permitem avaliar a intensidade e duração destes sistemas.…”

“…Uma situação de bloqueio atmosférico do tipo dipolo sobre o oceano é o ambiente ideal para a transição tropical (TT), isto é, a transição de ciclone extratropical para tropical como descreve McTaggart-Cowan et al (2006). Em geral, a baixa desprendida (também chamada de Vórtices Ciclônicos em Altos Níveis -VCAN ou no inglês de cutoff low) em níveis médios e altos que compõe o bloqueio do tipo dipolo está associada às anomalias de vorticidade potencial (VP) ciclônica (Bluestein, 1993).…”