Prevalence of tornado-scale vortices in the tropical cyclone eyewall

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 115; no. 33; pp. 8307 - 8310
• Main Authors: Wu, Liguang, Liu, Qingyuan, Li, Yubin
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 14.08.2018
• Subjects: Boundary layers; Clouds; Computer simulation; Convection; Cyclones; Domains; Hurricanes; Large eddy simulation; Mathematical models; Mesoscale convective complexes; Meteorology; Physical Sciences; Tornadoes; Tropical cyclones; Turbulence; Turbulent boundary layer; Vortices; Weather forecasting; tropical cyclone eyewall; large eddy simulation; tornado-scale vortex
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1807217115

Analyses of datasets from manned research flights that penetrated hurricane eyes and tropical cyclone (TC) damage surveys strongly suggest the existence of tornado-scale vortices in the turbulent boundary layer of the TC eyewall. However, their small horizontal scale, their fast movement, and the associated severe turbulence make the tornado-scale vortex very difficult to observe directly. To understand tornado-scale vortices in the TC eyewall and their influence on the TC vortex, mesoscale rainbands, and convective clouds, a numerical experiment including seven nested domains with the smallest horizontal grid interval of 37 m is conducted to perform a large eddy simulation (LES) with the Advanced Weather Research and Forecast (WRF) model. We show that most of the observed features associated with tornado-scale vortices can be realistically simulated in the WRF-LES framework. The numerical simulation confirms the existence of simulated tornado-scale vortices in the turbulent boundary layer of the TC eyewall. Our numerical experiment suggests that tornado-scale vortices are prevalent at the inner edge of the intense eyewall convection.