2015年7月20日6時30分(LST)左右於臺南新化區發生龍捲風，導致逾20棟民宅與無數農作物 損害，其中以山腳里、知義里及東榮里受災較嚴重。勘災資料顯示，致災路徑呈南北走向（幾乎沿國道 3號），總長度逾9 km，平均移速約12.0 ms-1，持續時間約15分鐘左右。 綜觀天氣顯示低層有一低壓中心位於海南島附近，由南中國海進到臺灣海峽的偏南風較強，帶來強 勁暖濕空氣；臺灣一帶之高空風(300 hPa)呈反氣旋式。此外，本研究個案發生位置正好位處高層分流區， 更有利於該區之劇烈對流系統發展；馬公氣象站探空圖顯示底層有較強垂直風切，且風徑圖顯示風向隨 高度順轉，顯示有利不穩定天氣發展。七股雷達回波顯示眾多對流胞出現在臺灣西南海面，產生龍捲風 的對流胞出現於臺南、高雄一帶海邊，上岸後迅速加強且伴隨明顯的中尺度氣旋，並出現鉤狀回波，雷 達徑向風場估計風切渦度約37.26 x10-3s-1。初步分析結果顯示，本研究個案生成之關鍵為位於其後方弧 形回波之外流邊界，該外流邊界與低層環境風場形成水平風切不穩定，不僅提供低層空氣強迫舉升，並 驅使外流邊界前緣形成一新生對流雲系。弧形回波後方明顯人流區，使得新生對流雲系追上本研究之中 尺度氣旋，並與之產生交互與合併作用，激發出迷你超大胞龍捲風。 過去臺灣地區的龍捲風主要是出現在梅雨季鋒面前緣的不穩定區域，本個案發生之綜觀環境較為不 同。致災路徑寬度均較以往個案寬，回波垂直剖面顯示似迷你超大胞之結構，即有著鉤狀回波與弱回波 區，以及中尺度氣旋的強度、水平及垂直尺度均較傳統超大胞為小。本案例乃臺灣地區內迷你超大胞首 次被分析之個案。

A tornado touched down at Hsin-Hua district in Tainan at 0630 LST on 20 July, 2015. More than 20 houses were damaged and severe agricultural damages, especially at Sun-Jao, Chih-Yi, and Dong-Rong villages. Based on damage survey, it shows the track was almost in north-south direction along freeway 3. The track length was about 9 km and lasted for about 15 minutes with average speed 〜12 m s—1. The synoptic condition has shown a low pressure center located near the Hai-Nan Island and strong southerly wind brought the warm moist air from South China Sea into Taiwan Strait area. The upper level (300 hPa) wind showed an anti-cyclone over the top of Taiwan area. In addition, the location of this case is right below the upper level diffluent area where is much favorable for severe convection to develop. The Mar-Kong sounding has shown strong low level wind shear and veering hodograph indicated an unstable atmosphere for severe weather to develop. A large area of convective cells located over the ocean at southwest side of Taiwan was observed from Chi-Gu radar. The cell that produced this tornado appeared near the Tainan coastal line. As soon as this cell made landfall, the intensity of mesocyclone greatly strengthened and the hook echo was evident. The maximum shear vorticity estimated is about 37.26 x 10-3 s-1. Based on our analysis, the outflow boundary from the back (southwest) side played an important role left the air upward and then triggered the tornado. According the past studies, tornadoes mainly occur at the leading portion of Mei-Yu fronts. However, the synoptic set-up is quite different in this case. The width of tornado damage path is generally broader compared to the previous cases based on the damage survey. The vertical profile of radar echo indicates the system is very similar to “mini supercell” type structure, i.e. hook echo, weak echo region, and intense mesocyclone (slightly weaker than typical supercell). It horizontal and vertical dimensions is compatible but smaller than supercell. This study provides the first study of minisupercell tornado in Taiwan area.