In traditional simulations of heavy rainfall events,the regional model is often initialized by using a global reanaly-sis dataset and a cold start method.An alternative to using global analysis data is to gradually introduce the analysis field via an incremental analysis update(IAU)method under the replay configuration.We found substantial differ-ences in the forecast of a heavy rainfall event in southern China between a precipitation forecast using the traditional method and a forecast using the IAU method in the Tropical Regional Atmospheric Modeling System(TRAMS),based on the ECMWF global analysis.The IAU method is efficient in removing spurious high-frequency gravity wave noise,especially when the relaxation time is more than 90 min.The regional model needs to be pre-integrated for about 12 h to warm up the convective system in the background field.The improvement by the IAU method is supported by verification of simulations over 1 month(1-30 April 2019).In general,the IAU technique improves the initialization and spin-up process in the simulation of the heavy rainfall event.