1415号“海鸥”台风龙卷天气过程分析

Analysis of the Tornado Weather Process of No.1415 kalmaegi Typhoon

2014年9月16日夜间,第15号台风"海鸥"外围螺旋雨带中产生龙卷,袭击了广东省佛山市三水区白坭镇。通过现场灾情勘察、群众走访、新一代雷达观测等资料的综合分析,确定这次龙卷强度为EF1级。分析其发生发展的环境背景、雷达回波特征,并与相似台风路径下无龙卷产生的1409号超强台风"威马逊"环境条件对比,结果表明:龙卷发生在登陆台风"海鸥"移动方向的右后侧,对应上空200 h Pa为辐散区,500 h Pa为副热带高压和"海鸥"之间的强东南气流汇合处,从925 h Pa到500 h Pa强东南急流轴走向一致、上下叠加在珠江口附近,地面存在触发对流的东路弱冷空气和中尺度辐合线。环境条件呈弱的条件不稳定,对流有效位能(CAPE)小、抬升凝结高度(LCL)低、垂直风切变和风暴相对螺旋度(SRH)大;产生龙卷的对流风暴属于低质心的微型超级单体风暴,速度图上低层存在强中气旋,中气旋中心伴有TVS,中气旋和TVS尺度比较小、垂直伸展高度比较低,强中气旋、TVS分别早于龙卷14 min、8 min出现。龙卷出现在微型超级单体风暴右后侧钩状回波顶端、TVS附近。分析还表明,相似台风路径下,台风"海鸥"(有龙卷出现)和超强台风"威马逊"(无龙卷出现)的环境条件明显差异主要体现在0~1 km的低层垂直风切变和SRH上,后者的0~1 km垂直风切变和SRH均明显偏小,不利于微型超级单体风暴的出现。

On the night of September 16,2014,a tornado broke out in the spiral rain belt around Typhoon No.15 kalmaegi and struck Baini Town,Sanshui District,Foshan City,Guangdong Province.The tornado strength was determined to be EF1 level by comprehensive analysis of the disaster investigation,mass visits and new generation radar observations.The environmental background and radar echo characteristics of typhoon occurrence and development are analyzed.The results show that the tornado occurs at the right rear of typhoon kalmaegi moving direction and the upper 200 hPa is the divergence area,and 500 hPa is the subtropical high.The strong southeasterly jet from 925 hPa to 500 hPa moves in the same direction and superimposes on the upper and lower sides near the Pearl River Estuary at the confluence of the strong southeasterly air pressure and the kalmaegi.Weak cold air and the mesoscale convergence line triggering convection exist on the ground.The environment condition is weak and unstable,the convective effective potential energy(CAPE)is small,the elevation condensation height(LCL)is low,the vertical wind shear and the storm relative helicity(SRH)is large;the convective storm which produces tornado belongs to the micro super-cell storm with low center of mass,and there is strong mesocyclone in the lower layer of the velocity chart,and the mesocyclone center is accompanied by TVS.The mesocyclone and TVS have smaller scale and lower vertical extension height,and the strong mesocyclone and TVS appear earlier than tornado 14 min and 8 min respectively.The tornado appears on the right rear side of the miniature supercell storm,near the top of the hook echo and near TVS.The analysis also shows that the environmental conditions of typhoon kalmaegi(with tornadoes)and super typhoon Wilmathon(without tornadoes)are significantly different under similar typhoon paths,which are mainly reflected in the low-level vertical wind shear of 0-1 km and SRH.The latter s 0-1 km vertical wind shear and SRH are obviously smaller than those of the former and aren t conduclve to the appearance of mini supercells.The emergence of body storms.