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Tropical depressions formed over the South China Sea usually produce severe flooding and wind damage when they develop into a storm and make landfall. To provide an early warning, forecasters should know when, and if, a tropical depression will develop into a tropical storm. To better understand and predict such development, we examine the dynamic and thermodynamic variables of 74 tropical depressions over the South China Sea, 52 of which developed into storms, hereafter "developing," with the remaining being classified as "nondeveloping." Using the National Centers for Environmental Prediction Final (NCEP FNL) data, verified with ECMWF forecast data, we examine the dynamic and thermodynamic statistics that characterize these tropical cyclones. Based on these characteristics, we propose seven criteria to determine whether a tropical depression will develop. Five had been used before, but two new criteria are also found to be useful. These two are associated with the diabatic heating rate and help to determine whether a tropical cyclone diurnal cycle exists and whether the convection system remains intact in the center: 1) presence of a regular diurnal variation of the diabatic heating rate at the center and 2) occurrence of specific peaks in the radiative-heating profile. We test all seven criteria on all tropical depression cases in 2018/19 before the system developed or decayed, showing that these criteria can help to operationally identify whether or not a tropical depression develops into a tropical storm with an average lead time of 36.6 h. Significance Statement: Tropical cyclones formed over the South China Sea usually produce severe flooding and wind damage. What determines if a given tropical depression will develop into a storm? We examine the dynamic and thermodynamic characteristics of tropical cyclones over the South China Sea, finding that established criteria plus characteristics of the diabatic heating rate can separate the developing from the nondeveloping cases. Applying these criteria to 11 tropical depression cases, we show that they can help forecasters predict whether or not a tropical depression will develop into a tropical storm. [ABSTRACT FROM AUTHOR]

This study investigates the rainfall asymmetry of tropical cyclones (TCs) in the process of making landfall in Guangdong (GD), south China, on the basis of satellite‐based and reanalysis precipitation data. We mainly focus on TC rainfall asymmetry, its main influencing factor and its change in the process of landfall, and the difference between different El Niño–Southern Oscillation (ENSO) phases. The results reveal that vertical wind shear (VWS) is the dominant influencing factor of TC rainfall asymmetry in GD. The rainfall maximum is located in downshear left of VWS. The TC rainfall asymmetry has little change in the process of making landfall, though the rain rate decreases. Both the phase and amplitude of TC rainfall asymmetry have no significant change from 24 hr prior to landfall to 12 hr after landfall. The rainfall maximum steadily lies in downshear left. The amplitude of rainfall asymmetry is about 50%, suggesting that the asymmetric rainfall is about half of the axisymmetric rainfall. There is no obvious difference in TC rainfall asymmetry between El Niño, La Niña, and neutral years. [ABSTRACT FROM AUTHOR]