Sensitivity of Numerical Simulations of Hurricane Harvey to Cloud Microphysical Schemes, Data Assimilation, and Cloud Initiation

A momentous hurricane, Harvey, that evolved over the Gulf of Mexico and greatly impacted Texas and Louisiana with strong winds and historical rainfall amounts from 26 to 30 August 2017, is studied with emphasis on its microphysical characteristics and their influences on the hurricane evolution. A sequence of high-resolution mesoscale simulations was performed with an advanced research version of the Weather Research and Forecasting (WRF ARW) model. First, several microphysical schemes were tested and analyzed to examine the sensitivity of numerical simulations of the forecast track, intensity, and rainfall amounts. It is found that the accurate simulations of Harvey’s track, structure, and rainfall before and after the landfall are very sensitive to the choice of the microphysical schemes. Further diagnoses are conducted to explain the implication of these sensitivities for the controlling factors that cause the massive rainfall and kinematic characteristics of Heavey. Additional simulations with the assimilation of conventional data, as well as cloud analysis derived from radar reflectivity, are being performed using WRF model with the Gridpoint Statistical Interpolation (GSI) system. The impact of integration of these observations on the forecast of Harvey’s track and subsequent precipitation are assessed.