The Spin-up Process of a Cyclone Vortex in a Tropical Cyclone Initialization Scheme and Its Impact on the Initial TC Structure

The scheme developed by Nguyen and Chen (2011) is used to produce 18 TCs (2004-2013) over the Northwestern Pacific that are well adjusted to the environment. The environment, including SST, in which the storm is embedded has a significant effect on the intensity and rainband patterns of these TCs. During the early season, TCs have a tendency to exhibit a "9" type asymmetric structure with an upper-level outflow channel extending southwestward from the southeastern quadrate of the storm. At low levels, the convergence area between the TC circulation and the southwesterly monsoon flow is a favorable location for the development of spiral rainbands. Late season TCs have a tendency to produce a "6" type storm structure with an outflow channel extending northeastward from the northwestern part of the eyewall, especially when an upper-level cold low or trough is present to the northwest of the storm. At low levels, the convergence of the northeasterly monsoon flow and the TC circulation is favorable for the occurrences of spiral rainbands. For intense TCs that underwent an eyewall replacement cycle, the scheme also shows considerable skill in reproducing the concentric eyewall structure.