An observational study of tropical cyclone spin-up in Supertyphoon Jangmi and Hurricane Georges
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Authors
Sanger, Neil T.
Subjects
Tropical cyclone spin-up
vortical hot towers
Supertyphoon Jangmi
Hurricane Georges
tropical cyclone intensification
rapid intensification
rotating deep convection
tropical cyclone boundary layer
vortical hot towers
Supertyphoon Jangmi
Hurricane Georges
tropical cyclone intensification
rapid intensification
rotating deep convection
tropical cyclone boundary layer
Advisors
Montgomery, Michael
Date of Issue
2011-12
Date
December 2011
Publisher
Monterey, California. Naval Postgraduate School
Language
Abstract
An observational study of tropical cyclone spin-up is performed using dropsondes and satellite imagery from Supertyphoon Jangmi and Hurricane Georges. Additionally, ELDORA data are analyzed in Tropical Storm Jangmi. The dropsonde analysis shows that the peak tangential wind occurs persistently within the boundary layer and suggests that significant supergradient winds are present there. However, as a result of data limitations arising from asymmetries and irregular placement of dropsondes in both time and space, a strongly conclusive statement about the presence of supergradient winds in Tropical Storm Jangmi is not possible. A dense deployment of dropsondes across the RMW is recommended to resolve the pressure gradient with sufficient accuracy to validate that supergradient winds exist at the tropical storm stage. An examination of ELDORA data in Tropical Storm Jangmi indicates that multiple rotating updrafts are present near the eye underneath cold cloud tops of -65C. Analysis of the infrared satellite imagery from both storms suggests that rotating updrafts are omnipresent before and during rapid intensification. The findings of this study support a new theoretical model positing that spin-up of the maximum winds occurs within the boundary layer and rotating deep convective cells are predominant during tropical cyclone intensification.
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Format
xviii, 159 p. : ill. ; 28 cm.
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.