Abstract The radius of maximum wind (RMW) has been found to contract rapidly well preceding rapid intensification in tropical cyclones (TCs) in recent literature but the understanding of the involved dynamics is incomplete. In this study, this phenomenon is revisited based on ensemble axisymmetric numerical simulations. Consistent with previous studies, because the absolute angular momentum (AAM) is not conserved following the RMW, the phenomenon can not be understood based on the AAM-based dynamics. Both budgets of tangential wind and the rate of change in the RMW are shown to provide dynamical insights into the simulated relationship between the rapid intensification and rapid RMW contraction. During the rapid RMW contraction stage, due to the weak TC intensity and large RMW, the moderate negative radial gradient of radial vorticity flux and small curvature of the radial distribution of tangential wind near the RMW favor rapid RMW contraction but weak diabatic heating far inside the RMW leads to weak low-level inflow and small radial absolute vorticity flux near the RMW and thus a relatively small intensification rate. As RMW contraction continues and TC intensity increases, diabatic heating inside the RMW and radial inflow near the RMW increase, leading to a substantial increase in radial absolute vorticity flux near the RMW and thus the rapid TC intensification. However, the RMW contraction rate decreases rapidly due to the rapid increase in the curvature of the radial distribution of tangential wind near the RMW as the TC intensifies rapidly and RMW decreases.
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Why Does the Initial Wind Profile Inside the Radius of Maximum Wind Matter to Tropical Cyclone Development?
This study examines the possible dependence of tropical cyclone (TC) development on the initial winds inside the radius of maximum wind (RMW) through ensemble axisymmetric numerical simulations. Results demonstrate that the vortex with higher initial winds inside the RMW favor larger surface enthalpy flux and thus faster moistening and earlier convective organization in the inner core, significantly shortening the initial spinup period. Higher inertial stability associated with higher winds inside the RMW implies higher eyewall‐heating efficiency, giving rise to higher intensification rate in the subsequent intensification stage but little difference in the steady‐state intensity. The results are confirmed with several sensitivity experiments using different model parameters and three‐dimensional simulations using the same model and configuration. The findings from this study strongly suggest that the realistic representation of the initial inner‐core winds is key to skillful TC intensity forecasts by numerical models and routine high‐resolution observations of the inner‐core wind structure are urged for improving TC intensity forecasts.
more » « less- Award ID(s):
- 1834300
- NSF-PAR ID:
- 10371885
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 127
- Issue:
- 16
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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