Structural Changes Preceding Rapid Intensification in Tropical Cyclones as Shown in a Large Ensemble of Idealized Simulations

• DOI: 10.1175/jas-d-17-0177.1
• Publication Date: 2017-12-06T15:25:14Z
• Authors: Yoshiaki Miyamoto; David S. Nolan
• Keywords: Eye; Mesocyclone; Dimensionless quantity

Abstract Structural changes that precede rapid intensification (RI) of tropical cyclones (TCs) are examined in a full-physics model by conducting large ensemble (270) idealized TC simulations. The processes leading to RI representative case with moderate shear consistent previous studies for weakly sheared cases. most distinct the vortex tilt and size begin decrease more rapidly 6 h before onset RI. A vorticity budget analysis upper layer around low-level center reveals vertical is increased advection, stretching, tilting terms RI, whereas horizontal advection small. Thus, upright structure not achieved through alignment process but rather built upward deep convection. simulations generated changing intensity initial vortex, magnitude wind shear, translation speed. members show control many studies: gradually increases, radius maximum tangential (RMW) decreases, flow becomes symmetric, convergence approaches winds. dimensionless parameter representing tendency formation vertically considered. product this local Rossby number significantly larger TCs exhibit next 24 h.