[Eoas-seminar] Reminder: Meteorology Masters Defense: Federico Di Catarina Seminar, Thursday July 5, 2018, 3:30 AM, LOV 353

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Tue Jul 3 12:10:11 EDT 2018


Meteorology Seminar



Federico Di Catarina

M.S. Meteorology Candidate



Title:  ON THE PREDICTABILITY and Structure OF SECONDARY EYEWALLS in HWRF SIMULATIONS OF TROPICAL CYCLONE Harvey (2017)

Major Professor:  Dr. Jeffrey Chagnon

Date: Thursday, July 5th             Time: 3:30 PM



Location: Werner A. Baum Seminar Room (353 Love Building)
(Please join us for refreshments served outside room 353 Love @ 3:00 PM)


ABSTRACT

Hurricane Harvey (2017) spawned from a westward propagating tropical wave in the Atlantic and then tracked across the southern Caribbean Sea, the Yucatán Peninsula, and lastly over the Gulf of Mexico, where it quickly intensified into a category 4 (on the Saffir-Simpson Scale) tropical cyclone. As a mature hurricane, Harvey underwent an eyewall replacement cycle which led to structural and intensity changes hours before making landfall over the Texas central coast.
This study investigates the structure and predictability of secondary eyewalls in 20 forecast simulations of Tropical Cyclone Harvey produced by the 2017 operational Hurricane Weather Research and Forecast (HWRF) System. To understand the predictability of secondary eyewalls, the secondary eyewall-producing simulations must be distinguished from the non-secondary eyewall-producing simulations. Thus, a diagnostic method of subjectively detecting secondary eyewalls in forecast data is developed. The diagnostic method identifies specific secondary eyewall traits that have been studied and documented in literature. The results show that most of the simulations (80%) produce a secondary eyewall. While the secondary eyewall-producing simulations are initialized over the ocean, the unsuccessful simulations, on the other hand, are initialized over or just west of the Yucatán Peninsula.
To study the relationship between land-storm interaction and secondary eyewall simulation, a comparison is made between the successful simulations initialized over the Caribbean Sea (which tracked over the Yucatán Peninsula) and the unsuccessful runs. For both sets of simulations, the effect of land-storm interaction led to temporary storm weakening while over the Yucatán Peninsula. However, this interaction has respectively a greater negative effect on vortex spin-up and organization on those simulations initialized over land. A possible explanation for this discrepancy could be related to a systematic and abrupt increase in the simulated surface latent heat fluxes over the Yucatán Peninsula that occurred at 1800Z in each day of simulation. The storms associated with the successful simulations are conveniently located over land during the abrupt increases in surface latent heat fluxes and therefore reintensify much faster, while the non-secondary eyewall-producing storms are not. It is possible that this and/or other land-surface characteristics simulated by HWRF may each have a deterministic effect on whether simulations initialized over or near land produce secondary eyewalls or not.

Shel McGuire
Florida State University
Academic Program Specialist
Department of Earth, Ocean, & Atmospheric Science
600 West College Avenue, 410 Love Building (Meteorology)
Tallahassee, FL 32306
850-644-8582

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