Characteristics and Trends in Short‐Duration Heavy Rain in Wet‐Season in Hong Kong

ABSTRACT This study examines the characteristics and trends of heavy rain events (hourly rainfall ≥ 30 mm) in Hong Kong from 2000 to 2024, with a focus on short‐duration events (1–3 h) in wet season (April–October), using a homogenised dataset from 114 automatic rain gauges. While longer‐duration (> 3 h) events tend to be more widespread, short‐duration events are highly localised with 60% confined to one or two small ‘zones’, leading to a lower issuance rate of local Rainstorm Warnings. While longer‐duration events generally exhibit higher maximum hourly rainfall, short‐duration events can occasionally produce intense rainfall (> 100 mm h −1 ). Unlike longer‐duration events, which are predominantly associated with surface troughs (troughs of low pressure), short‐duration events are primarily driven by local convective processes under weak synoptic forcing. Such processes lack clear large‐scale synoptic drivers. Longer‐duration events are more frequent during midnight and early morning hours, whereas short‐duration events peak around early afternoon. A statistically significant increasing trend in short‐duration heavy rain events (3.4 events per decade) is observed, primarily due to other mechanisms rather than surface troughs or tropical cyclones. Regionally, the New Territories East shows a substantial contribution to this territory‐wide trend. Notably, ‘localised’ short‐duration events account for nearly 90% of the overall trend, reflecting a shift towards more frequent, brief, and localised heavy rain events in Hong Kong.