2026/04/23 by Jimmy Yunge, David S. Nolan · 1 voice
Earth and Planetary Sciences · #Tropical and Extratropical Cyclones Research #Meteorological Phenomena and Simulations #Ocean Waves and Remote Sensing
paper · doi:10.1175/mwr-d-25-0203.1
Abstract Observational and numerical studies of intense tropical cyclones (TCs) have occasionally noted the existence of small-scale vortical eddies along the inner edge of the eyewall in the low–midtroposphere, which appear in plan-view radar reflectivity as closely spaced filamentary, cellular, lobed, or scalloped echoes protruding inward from the primary deep convective ring. Using high-resolution NEXRAD data, this study examines qualitative characteristics of these wave-like coherent structures in case studies of three Atlantic hurricanes. Signatures of these coherent structures in radar base moment data, including their wave-like echo pattern, Doppler velocity perturbations, and elevated spectrum widths, are generally most pronounced at lower radar elevations and diminish with altitude. The wave-like echoes are associated with alternating positive–negative values of azimuthal Doppler velocity shear, with individual small-scale reflectivity structures approximately collocated with enhanced positive (cyclonic) azimuthal shear. These patterns, albeit sensitive to sampling factors, formed the basis from which similar wave-like structures were identified in 11 additional North Atlantic and Pacific TCs. These coherent structures were found predominantly to the left (for Northern Hemispheric storms) of the environmental vertical wind shear vector, forward and left of storm motion, and in offshore flow, implying a role of asymmetric boundary layer dynamics in their development. Our results indicate that these coherent structures are not unique to high-end TCs, and the wide range of storm organization and environments over which these structures appeared suggests that they are an intrinsic element of TC inner-core dynamics and may constitute a distinct class of TC features. Significance Statement The evolution and maximum intensity of tropical cyclones (TCs) are strongly influenced by inner-core turbulent structures and their interactions with the primary vortex, and therefore, an improved understanding of the nature of TC turbulence is likely to advance the accuracy of operational forecasts. This study examines the shared radar characteristics of a class of organized turbulent eddies in the eyewall that the TC dynamics and aircraft reconnaissance communities have historically observed, but whose prevalence and conditions leading to their development remain highly obscure. The radar data presented here support the existence of these organized eddies as a unified phenomenon, laying groundwork for future study on their underlying mechanisms and real-world forecast and safety implications.