Environmental Characteristics of Intensifying and Weakening Tropical Cyclones in the North Atlantic and Western North Pacific Basins

The intensification and decay of a tropical cyclone (TC) is controlled by the evolving large-scale environment (including important factors such as ocean heat fluxes into the storm and vertical shear) and internal dynamical processes. While these processes operate on different spatial and temporal scales, it is by no means a pure dichotomy – scale interactions are prominent as well. Historically, this multi-scale nature of TC intensity change has been a great a challenge for forecasters.

In recent years, global analysis data quality has improved significantly due to better data assimilation techniques and inclusion of more remotely sensed observations. In this light, a systematic study is conducted to objectively re-examine the role of environmental factors in governing intensity change. The Joint Typhoon Warning Center and National Hurricane Center best track data from 2003-2008 is used in conjunction with the Navy Operational Global Atmospheric Prediction System (NOGAPS) daily global analysis and TRMM Microwave Imager data to obtain the composite environmental characteristics of storms undergoing intensifying and weakening episodes of varying magnitudes: (i) rapidly intensifying, (ii) intensifying, (iii) neutral, and (iv) weakening. The composites are used to assess the distinguishing features in the large-scale environment between each intensity change group, and to compare and contrast the similarities and differences between the two basins.