Practical and Intrinsic Predictability of Wave‐Convection Coupled Bands Over Southern China

Abstract The practical and intrinsic predictability of wave‐convection coupled bands that occurred near the south coast of China on January 30, 2018 lasting nearly 10 hr are investigated through convection‐permitting ensembles and relevant sensitivity experiments. Although almost all 20‐member ensembles can capture the wavelike pattern of convective bands, their wavelength and period vary among the ensembles. The GOOD and POOR runs are further conducted and initialized using the composite of initial conditions from good and poor members selected based on the performance of the simulated wave characteristics. Both the GOOD and POOR runs exhibit wave ducting structures for gravity waves, but the GOOD run tends to have higher precipitable water over the land, which results in a more evident wave pattern of convective bands on land in the GOOD run. Their differences in precipitable water are mainly attributed to the differences in the initial conditions of humidity and temperature at low‐middle levels. The practical predictability depends on the correct initial state in terms of thermodynamics, and to a lesser degree on physical parameterizations. To further explore their intrinsic predictability, a series of sensitivity experiments were performed with the linear weighted initial conditions from the GOOD and POOR runs. The pattern of wave‐convection coupled bands is generally predictable (forecast lead time <∼12 hr) but their phase (the exact location of each band) has an intrinsic predictability barrier even with minute initial perturbations due to the rapid small‐scale error growth associated with gravity waves and moist convection.