Publication Abstracts

Ramsay et al. 2009

Ramsay, H.A., L.M. Leslie, and J.D. Kepert, 2009: A high-resolution simulation of asymmetries in severe Southern Hemisphere Tropical Cyclone Larry (2006). Mon. Weather Rev., 137, 4171-4187, doi:10.1175/2009MWR2744.1.

Advances in observations, theory and modeling have revealed that inner-core asymmetries are a common feature of tropical cyclones (TCs). In this study, we investigate the inner-core asymmetries of a severe Southern Hemisphere tropical cyclone, TC Larry (2006), using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5) and the Kepert-Wang boundary layer model. The MM5-simulated TC exhibited significant asymmetries in the inner-core region, including rainfall distribution, surface convergence and low-level vertical motion. The near-core environment was characterized by very low environmental vertical shear and consequently the TC vortex had almost no vertical tilt. It was found that, prior to landfall, the rainfall asymmetry was very pronounced with precipitation maxima consistently to the right of the westward direction of motion. Persistent maxima in low-level convergence and vertical motion formed ahead of the translating TC, resulting in deep convection and associated hydrometeor maxima at about 500 hPa. The asymmetry in frictional convergence mainly was due to the storm motion at the eyewall, but was dominated by the proximity to land at larger radii. The displacement of about 30-120 degrees of azimuth between the surface and mid-level hydrometeor maxima is explained by the rapid cyclonic advection of hydrometeors by the tangential winds in the TC core. Our results for TC Larry support earlier studies which show that frictional convergence in the boundary layer can play a significant role in determining the asymmetrical structures, particularly when the environmental vertical shear is weak or absent.

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BibTeX Citation

@article{ra07600n,
  author={Ramsay, H. A. and Leslie, L. M. and Kepert, J. D.},
  title={A high-resolution simulation of asymmetries in severe Southern Hemisphere Tropical Cyclone Larry (2006)},
  year={2009},
  journal={Mon. Weather Rev.},
  volume={137},
  pages={4171--4187},
  doi={10.1175/2009MWR2744.1},
}

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RIS Citation

TY  - JOUR
ID  - ra07600n
AU  - Ramsay, H. A.
AU  - Leslie, L. M.
AU  - Kepert, J. D.
PY  - 2009
TI  - A high-resolution simulation of asymmetries in severe Southern Hemisphere Tropical Cyclone Larry (2006)
JA  - Mon. Weather Rev.
VL  - 137
SP  - 4171
EP  - 4187
DO  - 10.1175/2009MWR2744.1
ER  -

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