Sensitivity of Tropical Cyclone Outflow to the Environmental Flow

Our understanding of the predictability and processes associated with the tropical cyclone (TC) outflow, and its influence on TC intensity and structure remains elusive. Moreover, the role of the environmental flow on outflow and the key sensitivities require understanding. It remains an open question about how the environmental flow acts to modify the TC inner-core structure via first influencing the larger-scale outflow.

As part of the Office of Naval Research Tropical Cyclone Intensity (TCI) project, observational, theoretical and modeling studies are aimed at addressing these issues. Prior to investigating real TCs, idealized modeling is first used in this study to investigate the environmental interactions and main sensitivities. One hypothesis is that the TC can either strengthen or weaken depending on the distance between the TC and a jet or trough, and its subsequent effect on the secondary circulation. Additional sensitivities may be realized through variations in the altitude, size, and strength of the jet. The jet is set far enough from the TC in order not to have a substantial detrimental effect on TC intensity (like wind shear), but close enough to interact with the outflow. Initially following ideas proposed in the literature, the Weather Research and Forecasting (WRF) model is used to reveal the mechanisms behind how the outflow influences the TC via interacting with the environment. The results from several idealized experiments that aim to identify the dominant sensitivities will be reported.