Date of Award

Fall 2022

Document Type

Open Access Thesis

Department

Marine Science

First Advisor

Subrahmanyam Bulusu

Abstract

The Gulf of Mexico (GoM) is historically a favorable region for the formation, maintenance and intensification of tropical cyclones that frequently evolve into powerful hurricanes. These natural disasters threaten the basin’s innate habitat and wildlife diversity, and the expansive coastal economies and communities. The dominant ocean circulation feature in the GoM is the Loop Current System (LCS) which includes the Loop Current (LC) and its associated mesoscale eddy field. The LC originates at the Yucatán Channel, loops anticyclonically into the basin, and ends at the Florida Straits; further it produces both anticyclonic and cyclonic eddies. The existence of the LCS in the GoM influences the intensity evolution of overpassing tropical cyclones based on its variable ocean circulation dynamics. A case study of two temporally and spatially overlapping Hurricanes Marco and Laura (August 2020) is conducted to explain how their closeness was viable in the GoM, and further analyze atmospheric and oceanic conditions that influenced their respective evolutions while traversing the basin. Through the employment of a suite of satellite observations, NEMO (Nucleus for European Modelling of the Ocean) ocean model and National Hurricane Center (NHC) Atlantic tropical cyclone archives, the storms are evaluated regarding their ocean-atmosphere and biophysical interactions before, during, and after traversing the basin. The LCS, atmospheric wind shear and the GoM’s inherent thermodynamic properties explain the evolutions of each storm respectively and together. Further, biophysical modulations of the underlying ocean are explained via the physical response of an ocean to overpassing hurricanes.

The LCS’s circulation characteristics can influence tropical storm intensity. The warm, anticyclonic, LCS features are the LC itself and the associated anticyclonic eddies (AEs) it sheds irregularly; these warm features are of particular interest because they have greater values of ocean heat content (OHC) and a deeper mixed layer (ML) depth which favor storm maintenance and intensification. Tropical cyclones traversing the GoM during 1993 to 2020 are sampled to describe relationships between rates of intensification and instantaneous ocean circulation. It is concluded that it is well founded to attribute periods of rapid intensification to interactions with regions where a warm-core feature of the LCS is highly influential. Altimetric satellite observations are utilized along with the NHC Atlantic tropical cyclone best track archives to complete the investigation. The GoM is validated as a high-risk region for the intensification of tropical cyclones because of its inherent ocean circulation characteristics observed in both temporally short and long investigations. Further, in the GoM it is imperative to incorporate data that initializes the instantaneous position of the LCS when forecasting tropical cyclones due to its profound influence on storm intensification.

Rights

© 2022, Emily Nichole Eley

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