Diagnosis and Numerical Modeling of an Explosive Cyclone over the Northwestern Pacific

An explosive cyclone that took place over the Northwestern Pacific from 12 UTC 18 to 18 UTC 21 November 2007 was investigated. The synoptic situations and structure of this cyclone were documented by using the 1°×1° final analysis data of the National Center for Environmental Prediction. This cyclone developed explosively around 18 UTC 19 and reached its maximum deepening rate (MDR, 1.3 Bergeron) around 06 UTC 20 November 2007. At its MDR moment, the surface cyclone center was located in the downstream of the upper-level trough and northern entrance zone of the upper-level jet. The diagnosis using Zwack-Okossi equation suggested that cyclonic-vorticity advection and warm air advection acted to deepen this cyclone, while adiabatic cooling suppressed its development. In an investigation of this cyclone development, numerical sensitivity results obtained by using the Weather and Research Forecasting model showed that the latent heat release in the lower level had less contribution, whereas the surface sensible and latent fluxes played important roles. With a warmer ocean surface, the cyclone tended to intensify. Two topography tests were designed to examine the mountain influences on the development of this cyclone: removing a mountain and doubling the height of a mountain. Results show that the Changbai Mountains suppressed the development of the cyclone by preventing the southern moisture air from invading the inland. Without the moisture air, no latent heat release occurs when this cyclone passes over the Changbai Mountains.