Slow Versus Rapid Intensification of Tropical Cyclones in Idealized Simulations Using Soundings from Reanalysis

The large-scale environment, mainly wind and moisture, is known to influence the intensification rate of tropical cyclones (TCs). Lower 200-850 hPa wind shear and higher 500-700 hPa relative humidity are characteristic of the environment preceding rapid intensification (RI) events as compared to slower intensification (SI) rates. To investigate the key processes in RI versus in non-RI, the majority of previous idealized modeling studies have utilized highly simplified wind profiles. To produce more realistic profiles, this study uses average storm-relative profiles of environmental wind and moisture at onset for all RI and SI events between 1980-2021, based on ERA5 reanalysis data. Using the time-varying point downscaling technique within the Weather Research and Forecasting (WRF) Model, the environment around the idealized TC is nudged to the corresponding RI and SI wind and moisture profiles. The evolutions of the WRF wind shear and relative humidity in 3 separate annuli, 0-250km, 100-600km, and 200-800km, are compared with the corresponding climatological evolutions to determine how similar the wind and moisture evolution is between observations and the simulations. The vertical profiles of the wind and relative humidity are also analyzed between the RI and SI periods, to further elucidate differences that occur outside the standard levels used for calculations, in addition to nuances missed by taking large spatial averages. The simultaneous role of environmental wind and moisture, or lack thereof, will be investigated in the context of the ventilation hypothesis. TC tilt and asymmetries will also be explored to provide supplementary support for distinguishing between RI and SI processes.