2020年5月山东一共出现13次强对流天气过程，其中8次出现冰雹，共15市（93.8%）81站（65.9%）出现降雹，最大降雹次数4站次。10次出现10级以上雷暴大风，5次出现短时强降水，强对流次数之多、范围之广、强度之大、灾害之重为近10年来少见。其中，“5.17”强对流天气过程最为剧烈，其冰雹范围之广非常罕见，最大冰雹直径4.5cm，最大风速36.6m?s-1（12级），最大小时雨强56.9mm。利用ERA5再分析、加密自动气象观测站、多普勒天气雷达和闪电定位等资料，分析了2020年5月山东强对流天气特点及强对流多发的原因，并以“5.17”强对流天气过程为例，剖析了雷达回波特征和风暴内的垂直运动。结果表明：（1）副热带高压强度偏强，一方面有利于其外围的西南暖湿气流到达山东，另一方面阻挡西风带系统，导致前倾槽强度偏强，长时间维持在山东上空；500 hPa异常偏强的暖高压脊前西北气流携带的冷空气叠加在850hPa偏强的暖温度脊上空，造成山东上空长时间为位势不稳定大气层结。（2）在上述有利的天气背景下，山东省上空水汽充沛，CAPE偏大，冀鲁豫三省交界处气旋式辐合偏强，鲁中地区稳定存在一条辐合线，容易触发产生强对流天气，造成山东5月强对流天气频发。（3）对流风暴高度组织化，区域性的超级单体群以及一条长度超过500 km的强飑线是造成“5.17”强对流的直接原因，对流风暴内部的上升速度高达28 m?s-1。
There were thirteen severe convective weather processes in Shandong Province in May 2020, including 8 hailstorms, total 81 stations (65.9%) occurred hail in 15 cities (93.8%), with a maximum hail number of 4 times. There were 10 gales above level 10, and 5 short-time heavy precipitation. The frequency, coverage, intensity, and severity of disasters were rarely in recent 10 years. The "5.17" convective weather process was the most intense, its wide range of hail was very rare. The largest hail diameter was 4.5cm, the maximum wind speed was 36.6m?s-1 (level 12 ), the maximum rainfall intensity was 56.9mm . Based on ERA5 reanalysis, encrypted automatic meteorological observation station, Doppler weather radar and lightning location data, the characteristics of severe convective weather in Shandong Province in May 2020 and the causes of frequent severe convective weather were analyzed. Taking the "5.17" severe convective weather process as an example, the characteristics of radar echo and the vertical movement in the storm were analyzed. The results show that: (1) The stronger subtropical high not only favored the southwest warm moist airflow reaching Shandong, but also obstructed the westerly system, resulting in forward trough getting intensified and maintaining over Shandong Province for a long time. The cold air carried by the northwest airflow in front of the 500hPa enormously stronger warm high ridge was superimposed over the 850hPa unusually stronger warm temperature ridge, leading to an unstable atmospheric stratification over Shandong continuously. (2) Under above favorable weather background, the water vapor over Shandong Province was abundant, CAPE was larger, cyclonic convergence was strong at the junction of Hebei, Shandong and Henan provinces, and there was a stable convergence line in the middle region of Shandong, which was easy to trigger severe convective weather, resulting in frequent severe convective weather in Shandong in May. (3) The highly organized convective storm, regional supercell groups and a strong squall line with length more than 500km were the direct causes of "5.17" strong convection. The upward velocity inside the storm reached up to 28 m?s-1.