An Observational Study of Tropical Cyclone Spinup in Supertyphoon Jangmi (2008) from 24 to 27 September
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Authors
Montgomery, Michael T.
Sanger, Neil T.
Smith, Roger K.
Bell, Michael M.
Subjects
Advisors
Date of Issue
2014-01
Date
January 2014
Publisher
American Meteorological Society
Language
Abstract
An observational study of tropical cyclone intensification is performed using dropsondes, in situ flight-level
data, satellite imagery, and Electra Doppler Radar (ELDORA) during the spinup of Tropical Storm Jangmi
(2008) in the western North Pacific. This event was observed with research aircraft during the Tropical Cyclone
Structure 2008 (TCS08) field experiment over the course of 3 days as Jangmi intensified rapidly from a tropical
storm to a supertyphoon. The dropsonde analysis indicates that the peak azimuthally averaged storm-relative
tangential wind speed occurs persistently within the boundary layer throughout the spinup period and suggests
that significant supergradient winds are present near and just within the radius of maximum tangential winds. An
examination of the ELDORA data in Tropical Storm Jangmi reveals multiple rotating updrafts near the developing
eye beneath cold cloud top temperatures ≤ -65°C. In particular, there is a 12-km-wide, upright updraft
with a peak velocity of 9m s¯¹ with collocated strong low-level (z < 2 km) convergence of 2 x 10¯³ s¯¹ and
intense relative vorticity of 4 x 10¯³ s¯¹. The analysis of the corresponding infrared satellite imagery suggests
that vortical updrafts are common before and during rapid intensification. The findings of this study support
a recent paradigm of tropical cyclone intensification in which rotating convective clouds are important elements
in the spinup process. In a system-scale view of this process, the maximum tangential wind is found within the
boundary layer, where the tangential wind becomes supergradient before the air ascends into the eyewall updraft.
Type
Article
Description
The article of record as published may be found at http://dx.doi.org/10.1175/MWR-D-12-00306.1
Series/Report No
Department
Meteorology
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
Naval Postgraduate School
Office of Naval Research (Grant N001408WR20129),
National Science Foundation
Office of Naval Research (Grant N001408WR20129),
National Science Foundation
Funder
Office of Naval Research (Grant N001408WR20129)
Format
26 p.
Citation
Monthly Weather Review Volume 142 January 2014
Distribution Statement
Rights
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.