Date of Award

1-1-2017

Language

English

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College/School/Department

Department of Atmospheric and Environmental Sciences

Content Description

1 online resource (ii, x, 70 pages)

Dissertation/Thesis Chair

John Molinari

Committee Members

Kristen L Corbosiero

Keywords

Eyewall replacement cycles, Hurricanes, Vertical wind shear, Hurricane Bonnie, 1998, Wind shear

Subject Categories

Atmospheric Sciences

Abstract

Hurricane Bonnie (1998) was an unusually resilient hurricane that maintained intensity in 12–16 ms-1 vertical wind shear and during an eyewall replacement cycle from 23 – 25 August. This remarkable behavior was examined using observations from flight-level data, microwave imagery, radar, and dropsondes over the two-day period. The symmetric and asymmetric aspects of Bonnie’s eyewall replacement cycle were documented and compared to eyewall replacement cycles in other hurricanes. Similar to other observed eyewall replacement cycles, Bonnie exhibited the development, strengthening, and dominance of a secondary eyewall while a primary eyewall decayed. However, Bonnie’s structure was highly asymmetric due to strong 12–16 ms-1 vertical wind shear, in contrast to the more symmetric structures observed in other hurricanes undergoing eyewall replacement cycles. It is hypothesized that strong shear preferentially forced convection downshear, which was able to extend upshear and form a secondary eyewall through enhanced surface fluxes upshear. The larger radius of maximum winds after the eyewall replacement cycle completed might have aided Bonnie’s resiliency in shear by increasing the likelihood that diabatic heating would fall inside the radius of maximum winds. These observations of Hurricane Bonnie’s ability to maintain intensity in spite of high shear and an eyewall replacement cycle, both of which usually result in weakening, provide a new direction from which to view the intensity change issue in hurricanes.

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