Mechanisms and subseasonal prediction of severe freezing precipitation events in East China in early 2024

In February 2024, East China experienced two severe freezing precipitation (FP) events, causing record-breaking ice storms and snowfall hazards not observed since 2008. This study develops a method to identify FP occurrences at grid points and examines their mechanisms and predictability using reanalysis data and model outputs. Diagnostic results reveal that the 2024 FP events were driven by positive precipitation anomalies under the influence of a deep inversion layer. These anomalies were associated with enhanced Siberian High activity, which induced cold air intrusion forming a near-surface freezing layer, and warm advection creating a melting layer, linked to southerly anomalies in relation to suppressed tropical convection of the Madden-Julian Oscillation (MJO) over the Maritime Continent. Analysis of historical FP cases, including the 2008 event, indicates that Siberian High enhancement is a necessary condition for FP, consistently accompanying such events. However, FP magnitude is weakly correlated with Siberian High intensity and instead depends on the strength of suppressed convection anomalies over the Maritime Continent. Subseasonal-to-seasonal prediction models exhibited limited skill in predicting the 2024 FP occurrences beyond lead times of 2–3 pentads due to deficiencies in capturing Siberian High activity and cold air intrusion. The forecast skill of FP amounts further depended on model’s capability in capturing MJO-related convection. These findings emphasize the need to improve representations of mid-latitude and tropical systems in operational models to enhance subseasonal predictability of hazardous winter weather events.