| 摘要: |
| 【目的】分析广西暖区飑线的形成机理，为提升雷暴大风的预报预警服务质量提供参考。【方法】2023年4月19日来宾市出现一次范围广、极端性强的全市性雷暴大风天气过程，最大风速达34.1 m·s⁻¹，打破来宾历史记录。利用常规观测、雷达、卫星及ERA5再分析资料和数值模式等资料，对此次天气过程进行天气学诊断分析。【结果】（1）此次为暖区雷暴大风过程，初始阶段由多单体风暴造成，后通过自组织发展形成飑线继续南移影响造成全市性雷暴大风天气。（2）过程发生在上干冷下暖湿的不稳定层结中，低层暖平流增强热力不稳定，大的 CAPE 和 DCAPE、强的风垂直切变和中高层干区等提供有利的环境条件，地面辐合线、干线触发对流，冷池发展与对流单体自组织的正反馈作用促使飑线形成和维持。（3）来宾大范围大风主要出现在飑线的发展—强盛期，飑线阶段移动速度快、存在速度模糊、显著中层径向辐合、中气旋和风暴顶的辐散以及对流顶高、回波质心、VIL的快速下降均对极端大风的出现有指示意义。（4）主客观短期预报均对此次过程漏报，主要是对风暴能够通过自组织发展形成飑线继续南下影响考虑不足所导致。【结论】在短时临近预报中加强实况和中尺度对流回波的演变分析，及时发布预报预警信息，能够弥补短期预报的不足。 |
| 关键词: 暖区飑线；极端大风；云顶坍塌；对流自组织过程 |
| DOI： |
| 投稿时间：2024-05-16修订日期：2024-08-01 |
| 基金项目:广西气象局创新平台专项(BNCO-N202304)；广西青年科学基金项目(2023CXNSFBA026342)；广西气象科研计划重点项目(桂气科2023203)。 |
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| Analysis on Causes and Forecast Bias of the Extreme Gale in Laibin City on April 19, 2023 |
| Xu Yunjie,Zhai Liping,Li Shengyan,Liang Zhenqing,Ou Ye,Cheng Junqi |
| (Laibin Meteorological Office of Guangxi Zhuang Autonomous Region;Guangxi Zhuang Autonomous Region Meteorological Observatory;Laibin Meteorological Office of Guangxi Zhuang Autonomous Region，Guangxi Zhuang Autonomous Region Meteorological Technology Equipment Center,) |
| Abstract: |
| This paper analyzes the formation mechanism of a warm-sector squall line in Guangxi to provide a reference for improving the quality of severe thunderstorm and gale forecasting and warning services. On April 19, 2023, Laibin City experienced a city-wide severe thunderstorm gale event with a maximum wind speed of 34.1 m·s⁻¹, breaking the local historical record. Using conventional observations, radar, satellite, ERA5 reanalysis, and numerical model data, a synoptic diagnostic analysis of the event was conducted. Results show that: (1) This event was a warm-sector thunderstorm gale process. In its initial stage, multiple isolated storms occurred; through self-organization, they developed into a squall line that continued moving south, causing a city-wide gale. (2) The event occurred under an unstable thermal structure of cold-dry air aloft overlying warm-moist air below; enhanced low-level warm advection increased thermodynamic instability. Large CAPE and DCAPE, strong vertical wind shear, and a mid-to-upper-level dry layer provided favorable environmental conditions. Convergence lines and drylines at the surface triggered organized convection; cold-pool development and positive feedback with isolated storms promoted squall line formation and maintenance. (3) Widespread gales in Laibin mainly occurred during the squall line’s mature stage. During the squall line phase, rapid system motion, velocity folding in low-elevation radial velocity, pronounced mid-level radial convergence, mesocyclones, storm-top divergence, rapid decreases in echo-top height, echo centroid, and VIL all had indicative significance for extreme gale occurrence. (4) Both subjective and objective short-term forecasts missed this event, mainly due to insufficient consideration of storms self-organizing into a southward-propagating squall line. Strengthening real-time analysis and meso-scale convection echo tracking in short-term forecasts, and issuing timely warnings, can compensate for deficiencies in short-term forecasting. |
| Key words: warm-sector squall line; extreme strong wind; cloud-top collapse; convective self-organization process |
