Ground-based Doppler radar observations of wave-like coherent structures along the inner edge of the tropical cyclone eyewall.

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Bibliographic Details
Title:	Ground-based Doppler radar observations of wave-like coherent structures along the inner edge of the tropical cyclone eyewall.
Authors:	Yunge, Jimmy¹ (AUTHOR) jyunge@elms.hokudai.ac.jp, Nolan, David S.¹ (AUTHOR)
Source:	Monthly Weather Review. Jun2026, Vol. 154 Issue 6, p1-25. 25p.
Subjects:	Doppler radar, Coherent structures, Boundary layer equations, Vertical wind shear, Tropical cyclones
Geographic Terms:	North Atlantic Ocean
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 lower and middle troposphere, which appear in plan view radar reflectivity as closely spaced filamentary, cellular, lobed, or scalloped echoes protruding inward from the primary eyewall 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 eleven 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 structure 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. [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

Description
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 lower and middle troposphere, which appear in plan view radar reflectivity as closely spaced filamentary, cellular, lobed, or scalloped echoes protruding inward from the primary eyewall 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 eleven 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 structure 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. [ABSTRACT FROM AUTHOR]
ISSN:	00270644
DOI:	10.1175/MWR-D-25-0203.1