Abstract:Influenced by the weakening low pressure of Typhoon Doksuri, the Beijing-Tianjin-Hebei Region suffered the unprecedented extremely severe torrential rain from 29 July to 1 August 2023, with catastrophic floods in the Haihe River Basin causing serious casualties and economic losses. A preliminary analysis of this rarely seen severe precipitation event is conducted in this article based on conventional observations, S-band Doppler weather radar data, wind profile radar data, and ERA5 reanalysis data. The results show that this extremely severe torrential rain process was characterized by enormous accumulated rainfall, and long duration, affected significantly by terrain. Typhoons Doksuri and Khanun provided extremely favorable water vapor conditions, but the high pressure barrier formed in northern part of North China blocked the northward typhoons. The North China Region experienced three stages: intermittent rainfall, typhoon inverted-trough precipitation and convective precipitation during the weakening stage of the inverted-trough, and the superposition of precipitation areas in three stages was the main cause for the formation of the extremely severe torrential rain. During the stage of weakening inverted-trough, the shear line at 850 hPa moved slowly due to the obstruction of the Taihang Mountains, causing the long duration of precipitation. The atmosphere was in a near neutral state with stable rainfall intensity in the early stages. From the afternoon of 30 July, convective precipitation began to strengthen. The convergence line formed by the northerly wind which was generated by the outflow of the cold pool in the central rainfall area of Hebei Province and the surface southeast wind triggered the release of unstable energy and also strengthened the development of triggered convective cells into mesoscale convective system (MCS) in the high-energy area of southeastern Hebei. This MCS moved into Baoding, resulting in the “train effect”. The convergence line between the surface north wind generated by the cold pool of Taihang Mountains and the southeast wind triggered the release of unstable energy, which was the reason for the maintenance of severe precipitation in southwestern Hebei over the night of 30 July. On the morning of 31 July, a southeast low-level jet over 20 m·s-1 was established again, leading to the extremely severe torrential rain exceeding 110 mm·h-1 in the southern part of Beijing.