Geoscience Reference
In-Depth Information
FORMATION OF TROPICAL CYCLONE CONCENTRIC
EYEWALLS BY WAVE-MEAN FLOW INTERACTIONS
JIAYI PENG
International Pacific Research Center, University of Hawaii,
1680 East West Road, Honolulu, Hawaii, USA
TIM LI
Department of Meteorology and International Pacific Research Center,
School of Ocean and Earth Science and Technology,
University of Hawaii, Honolulu, Hawaii, USA
MELINDA S. PENG
Naval Research Laboratory, Monterey, California, USA
The role of two-way interactions between a symmetric core vortex and an
asymmetric disturbance in generating tropical cyclone (TC) concentric eyewalls
is examined in a nonlinear barotropic model. The results show that when an
asymmetric perturbation is placed outside of the radius of maximum wind, an
asymmetric disturbance develops in the inner region, resulting in a weakening
of the symmetric flow
in situ
, while the symmetric tangential wind gains
energy from the asymmetric perturbations in the outer region. This process
leads double peaks in the symmetric tangential wind profile. Further diagnosis
reveals that the distinctive evolution features in the inner and outer regions
are determined by the asymmetric up- (down-) shear tilting structure and so-
induced symmetry-to-asymmetry (asymmetry-to-symmetry) energy transfer.
There exists an optimal radius location for the initial perturbation to generate
most eciently a double-peak structure in the symmetric tangential wind
profile.
1. Introduction
Concentric eyewalls have been observed in the life cycle of strong tropical
cyclones (TC). Willoughby
et al.
12
identified a double eyewall structure
for hurricane Gilbert with the inner eyewall in the radius of 8-20 km
and the outer eyewall between 55 and 100 km. A more detailed analysis
of Gilbert
1
showed that the primary eyewall appeared first. During a
weakening stage of the storm, the outer eyewall formed. Later on, the outer
eyewall strengthened and contracted while the inner eyewall weakened.
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