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- Title
Looping tracks associated with tropical cyclones approaching an isolated mountain. Part I: Essential parameters.
- Authors
Huang, Yi-Chih; Lin, Yuh-Lang
- Abstract
Essential parameters for making a looping track when a westward-moving tropical cyclone (TC) approaches a mesoscale mountain are investigated by examining several key nondimensional control parameters with a series of systematic, idealized numerical experiments, such as U/Nh, Vmax/Nh, U/fLx, Vmax/fR, h/Lx, and R/Ly. Here U is the uniform zonal wind velocity, N the Brunt-Vaisala frequency, h the mountain height, f the Coriolis parameter, Vmax the maximum tangential velocity at a radius of R from the cyclone center and Lx is the halfwidth of the mountain in the east-west direction. It is found that looping tracks (a) tend to occur under small U/Nh and U/fLx, moderate h/Lx, and large Vmax/Nh, which correspond to slow movement (leading to subgeostrophic flow associated with strong orographic blocking), moderate steepness, and strong tangential wind associated with TC vortex; (b) are often accompanied by an area of perturbation high pressure to the northeast of the mountain, which lasts for only a short period; and (c) do not require the existence of a northerly jet. The nondimensional control parameters are consolidated into a TC looping index (LI), U2R2Vmax2hLy<inline-graphic></inline-graphic>, which is tested by several historical looping and non-looping typhoons approaching Taiwan’s Central Mountain Range (CMR) from east or southeast. It is found that LI < 0.0125 may serve as a criterion for looping track to occur.
- Subjects
TAIWAN; TROPICAL cyclones; BRUNT-Vaisala frequency; CYCLONES; TYPHOONS; WIND speed
- Publication
Meteorology & Atmospheric Physics, 2018, Vol 130, Issue 3, p333
- ISSN
0177-7971
- Publication type
Article
- DOI
10.1007/s00703-017-0533-x