Importance of the upper‐level warm core in the rapid intensification of a tropical cyclone

Abstract

[1] In this study, the rapid intensification (RI) of tropical cyclone is examined using a 72-h cloud-permitting prediction of Hurricane Wilma (2005) with a record-breaking intensity of 882 hPa. Results show the formation of an upper-level warm core from the descending air of stratospheric origin in the eye, which coincides with the onset of RI; it reaches the peak amplitude of more than 18°C from its initial conditions at the time of peak intensity. The descending air is associated with the detrainment of convective bursts in the eyewall, and it appears as (perturbation) cyclonic radial inflows above the upper outflow layer and causes the subsidence warming below. We hypothesize that the upper divergent outflow layer favors the generation of a warm core by protecting it from ventilation by environmental flows. Use of the hydrostatic equation shows that the warm core of stratospheric origin contributes more than twice as much as the lower-level warm column to the pressure change at the peak intensity of Wilma. Results suggest that more attention be paid to the magnitude of storm-relative flows and vertical wind shear in the upper troposphere, rather than just vertical shear in the typical 850-200 hPa layer, in order to reasonably predict the RI of tropical cyclones. Citation: Zhang, D.-L., and H. Chen (2012), Importance of the upper-level warm core in the rapid intensification of a tropical cyclone, Geophys.

Impacts of the Lower Stratosphere on the Development of Intense Tropical Cyclones

“…The 900-m resolution in the central domain is used to better capture small-scale features associated with DWC formation and better resolve the DWC structural features. As shown in previous studies (e.g., [11,14,19,27]), DWCs appear in the TC eye with a typical radius of 10-20 km, so high-resolution simulations are necessary to capture the detailed formation of the DWC structure in the vortex core.…”

“…As discussed in [11], an upper-level inflow may emerge if there exits a sufficiently strong inward pressure gradient in the 100-70 hPa layer. Two possible mechanisms for the development of such an inward pressure gradient are radiative cooling at the cloud top in the outer-core region, and the returning inflow associated with overshooting convective rings in the eyewall region as disccused in [19].…”

Climatology of overshootings in tropical cyclones and their roles in tropical cyclone intensity changes using TRMM data

“…3.2c) from the SI to RI initial category, but moderately deep and very deep precipitation do not increase until the later stage of RI (i.e., the RI continuing category; Figs Table 3.4. (2005) by Zhang and Chen (2012) showed that convective bursts occurred mostly in the upshear quadrant when the storm underwent RI. The largest area of > 1% occurrence of very deep precipitation is observed in SI storms (Fig.…”

On the Sensitivity of Tropical Cyclone Intensification under Upper-Level Trough Forcing

“…1). Shearinduced ventilation can weaken a TC through three concomitant processes: (i) a dilution of the upper-level warm core by outward fluxes of high u e and PV values, which causes the central pressure to rise through hydrostatic arguments (Frank and Ritchie 2001;Zhang and Chen 2012); (ii) convective downdrafts that flush low-entropy air into the boundary layer (Riemer et al 2010(Riemer et al , 2013; and (iii) shear-induced updrafts outside the eyewall that transport high-entropy air from the boundary layer, further weakening the midlevel radial gradient of moist entropy across the eyewall (Gu et al 2015). The importance of shear height on TC intensification is examined (Tang and Emanuel 2012;Shu et al 2013;Wang et al 2015) to possibly develop new metrics from the total vertical wind profile (Fig.…”