What Are the Finger-like Clouds Along the Inner Edge of Hurricane Eyewall?

Regular finger-like cloud features, sometimes referred to as misovortices or helical striations, with alternating updrafts and downdrafts along the inner edge of the hurricane’s eyewall have been frequently captured in LES-type simulations and occasionally observed in radar images. However, many aspects of these features, including their formation mechanism, three-dimensional structure, lifespan and temporal distribution, remain largely unknown. In this study, we conduct high-resolution (~100m grid spacing) idealized hurricane simulations using the GFDL SHiELD model to investigate these phenomena. Remarkably, we found that these finger-like features can be adequately captured even with a 500m horizontal grid spacing. These features first manifest when the surface maximum wind of the hurricane reaches about 60 m/s. Once initiated, they persist and propagate azimuthally along with the TC circulation. These features dominate the vertical velocity field in the lower 3 km of the troposphere along the inner edge of the eyewall. A kinetic energy budget analysis suggests they are likely generated by the shear instability caused by the strong azimuthal wind shear. The latent heat release in their updraft cores also can enhance their overturning circulations.