“艾云尼”台风龙卷天气过程分析

利用常规观测、地面自动气象站、多普勒天气雷达、现场灾调及互联网视频等资料,对2018年6月8日发生在广东省佛山市南海区大沥镇的1804号“艾云尼”台风龙卷天气过程进行分析。结果表明:龙卷发生在台风“艾云尼”登陆后前进方向的右后侧,强度为EF1级。高层辐散抽吸、中低空强劲的东南风急流叠加和地面中尺度辐合线的抬升触发作用是其有利的环流背景。对流参数表现为弱的对流有效位能和对流抑制能量、强低层风垂直切变、低抬升凝结高度和大的风暴相对螺旋度。产生龙卷的风暴为低质心微超级单体风暴,龙卷出现在钩状回波的弱回波区内。速度图上中气旋提前龙卷约30 min,临近龙卷发生时中气旋旋转速度增至最强,尺度缩小,底高降至最低,对龙卷预警有一定指示作用。

Analysis of the tornado weather process of Ewiniar typhoon

Based on the data from the conventional and automatic weather stations, Doppler radar, network videos, the disaster investigation and so on, the tornado weather process of No.1804 Ewiniar typhoon was analyzed.The results show that the tornado occurs on the right and rear side of the direction of typhoon Ewiniar after landing, with a strength level of EF1.The favorable circulation background includes the divergence suction at a high level, strong southeasterly jet stack at the middle and low level, and the lifting trigger of the mesoscale convergence line at the ground.The properties of atmosphere convective parameters are weak convective available potential energy and convective inhibitory energy, strong vertical wind shear at a low level, and low elevation condensation height and large relative helicity of a storm.The convective storm that produced the tornado is a low-mass micro-supercell one, and the tornado appears in the weak echo area of hook echo.On the velocity diagram, the meso-cyclone appears about 30 min ahead.The rotation speed of the meso-cyclone increases to the largest level near the occurrence of a tornado.Its size decreases, and its bottom height reaches to the minimum.All of these have a certain indicating effect for the early warning of the tornado.