Synoptic background conditions and moisture transport for producing the extreme heavy rainfall event in Valencia in 2024

From 26 October to 2 November 2024, Spain experienced a record-breaking rainfall event, with the most intense episode appearing in Valencia Province. During the event, Turis station recorded a historic 24-hour precipitation of 710.8 mm, exceeding the national annual average. This resulting flood led to widespread disruption and significant societal impacts. Synoptic analyses reveal that the event was dominated by a deep cut-off low extending through the entire troposphere and persisting for approximately 186 h. Background conditions were characterized by upper-level divergence, mid-tropospheric warm advection, and a strong southeasterly low-level jet, which promoted vertical motion and sustained moisture transport. The steep, funnel-shaped terrain along the eastern Iberian coast further triggered and enhanced the local convection. A 10-day backward Lagrangian moisture tracing using the HYSPLIT model identified the Mediterranean Sea as the primary moisture source (78.1 %), followed by northwestern Africa (8.5 %) and central-eastern Europe/the Black Sea (6.2 %). Low-level moisture transport was mainly driven by the cut-off low and a persistent Mediterranean high, while mid- to upper-level trajectories were associated with a preceding low-pressure system over the Mediterranean and the subtropical Atlantic high. These systems acted in sequence to relay moisture toward the Valencia region, and under the influence of the strongly rotating and convergent cut-off low—along with terrain-induced lifting—this moisture was rapidly uplifted, ultimately triggering the extreme rainfall event.

摘要

2024年10月26日至11月2日, 西班牙瓦伦西亚省遭遇罕见极端降雨, Turis站24小时降水量达710.8毫米, 引发严重洪涝灾害. 此次事件由持续186小时的深厚切断低压主导, 在高层辐散, 中层暖平流与低空东南急流共同作用下形成强垂直运动, 东海岸漏斗地形进一步增强对流. HYSPLIT后向追踪显示, 水汽主要来自地中海 (贡献率78.1 %), 其次为非洲西北部 (8.5 %) 和欧洲中东部/黑海 (6.2 %). 水汽由多个天气系统接力输送至瓦伦西亚, 最终在切断低压旋转辐合和地形抬升作用下, 引发此次破纪录降雨事件.