Land–Sea Contrast in the Diurnal Variation of Precipitation from Landfalling Tropical Cyclones

Recent composite analysis of landfalling tropical cyclones (TCs) suggests a rain-rate peak in the early morning, which contradicts the typically observed peak in convective precipitation over land seen in the late afternoon to early evening. We conducted a set of idealized simulations of TCs and analyzed observational data from landfalling Hurricane Harvey (2017) and TC Bebinca (2018), which both stalled near the shorelines. We show a distinct land–sea contrast in the diurnal variation of TC precipitation and peak rainfall over land lagging that over sea by 8–12 h in a TC that stalls at the shoreline. The lag might be reduced for TCs that move rapidly inland because of the time taken to respond to the change in the underlying surface from sea to land. The highest land surface temperature and maximum low-level buoyancy during the afternoon led to peak precipitation over land at this time. However, the peak precipitation over the sea in the early morning was generated by the increase in relative humidity caused by nighttime radiative cooling and enhanced instability.