An Examination of the Pressure–Wind Relationship for Intense Tropical Cyclones

Abstract

In this study, the dynamical constraints underlining the pressure?wind relationship (PWR) for intense tropical cyclones (TCs) are examined with the particular focus on the physical connections between the maximum surface wind (VMAX) and the minimum sea level pressure (PMIN). Use of the Rankine vortex demonstrates that the frictional forcing in the planetary boundary layer (PBL) could explain a sizeable portion of the linear contributions of VMAX to pressure drops. This contribution becomes increasingly important for intense TCs with small eye sizes, in which the radial inflows in the PBL could no longer be neglected. Furthermore, the inclusion of the tangential wind tendency can make an additional contribution to the pressure drops when coupled with the surface friction. An examination of the double-eyewall configuration reveals that the formation of an outer eyewall or well-organized spiral rainbands complicates the PWR. An analysis of a cloud-resolving simulation of Hurricane Wilma (2005) shows that the outer eyewall could result in the continuous deepening of PMIN even with a constant VMAX. The results presented here suggest that (i) the TC size should be coupled with VMAX rather than being treated as an independent predictor as in the current PWRs, (ii) the TC intensity change should be at least coupled linearly with the radius of VMAX, and (iii) the radial wind in the PBL is of equal importance to the linear contribution of VMAX and its impact should be included in the PWR.