台风远外围大范围强对流天气成因综合分析

为加深对台风外围发生的强对流天气的认识，提高对华南地区强对流天气潜势预报和预警的能力，利用广东中尺度天气监测网的多普勒雷达、自动站资料和NCAR／NCEP的再分析资料等对2004年8月发生在台风云娜外围一次强对流天气的天气形势背景、水汽、CAPE、SI、WI、垂直速度和海风辐合等进行了综合分析。结果表明：华南前期受副热带高压和云娜外围下沉气流作用，地面连续高温，使低层大气内能不断积蓄；台风云娜向西北移动的过程中，华南上空的副热带高压和下沉气流减弱，在其外围弱低压槽、海风辐合和干线共同作用下触发了强对流；台风外围的稳定度具有明显的波动性，强对流在台风外围螺旋云带末端的高温、不稳定和相对高湿舌发生；风指数WI用于华南地区雷雨大风预报比其它指数更有效。

Comprehensive Analysis on an Extensive Summer Severe Convection in Outer Periphery of Typhoon

In order to further understand the severe weather originating in the periphery of typhoons and improve the capability of severe weather potential forecast and warning, the synoptic background, water vapor, CAPE, WI, vertical velocity and sea breezes are analyzed on a severe convection weather occurring in outer periphery of Typhoon Rananim in August 2004 based on the Doppler radar, automatic weather station and NCAR/NCEP reanalyzed data etc. The continual heat wave in South China resulted from the subsidence from subtropical high and the periphery of Typhoon Rananim, consequently, internal energy is accumulated, and strong instable state is established. When the subtropical high weakened and the subsidence disappeared as a result of northwestward moving of Typhoon, the severe convection is triggered by the weak trough and sea breeze and a dry line. The stability outsides the typhoon is of fluctuant characteristics. The convection developed on an instable tongue with higher temperature and higher humidity that joint with the end of an exterior spiral cloud band of Typhoon Rananim. Wind Index is more available in forecasting thunderstorm wind gusts than other indexes in South China.