2009年8月，莫拉克颱風侵襲台灣，8月6日至8月9日，莫拉克颱風以其驚人雨勢，在南部山區創下破記錄的雨量，將南台灣較低窪平地淹沒，汪洋一片，豪雨山洪也引發山區各處極爲嚴重的土石流災害，小林滅村災難更震驚全世界。對於此次嚴重颱風災害，台灣社會各界投入許多救援物資與心力，學術界也紛紛投入自然災害之防災救災學術研究。本研究之目的在如何提昇颱風豪雨預報準確度，以便提升防災應變效率。作者依據所著《台灣颱風地形效應豪雨預警區之研究》，將已建立的“颱風地形效應豪雨預警區”應用於此次莫拉克颱風地形豪雨的研究。採用台北、信義、甲仙及花蓮等四地方之警戒區圖，驗證說明莫拉克颱風受地形效應所導致豪雨現象的區域差異；在方法上，以各地不同方位的地形剖面圖來判別不同風向的迎背，找出各地可能導致地形效應豪雨增強的風向，利用影像處理軟體，合成製作典型之颱風環流風向分布圖、颱風從不同方位來襲時各地之颱風風向風盤圖，以及搭配地形圖的各地颱風風向風盤地形合成圖。依據地形剖面之迎風背風關係分析結果，分劃出各地因颱風中心進入某特定位置範圍而可能帶來颱風地形效應豪雨之預警區圖。本文在實際操作上，採用300公里半徑爲警戒區範圍，以切合莫拉克颱風環流規模，分析結果與預期相當符合。本文認爲，要提昇颱風豪雨預報準確度與防災應變效率，一要注意以台灣整體爲大尺度前提下之中尺度地形影響，確實掌握區域差異，以建立預報信心；二是要以地方爲中心本位來思考，建立適合地方應用的豪雨預警制度，以切中各地方的需求。

Typhoon Morakot invaded Taiwan in August 2009. From August 6 to 9, Morakot brought amazing heavy rainfall which broke the southern Taiwan mountain areas records. The vast plain in southern Taiwan was in flood. Heavy rainfall of Morakot resulted in a lot of mudflows and landslides in mountains, and peoples of the world were shocked by the disaster of Shiao-Lin village. Peoples of Taiwan devoted all they can do to save the sufferer, and there were many scholars researching the natural hazards of Taiwan. In this research, how to promote the forecast of typhoon rainfall more accurate and how to prevent the disaster more effectively is the main research purpose. Based on the established models of forewarning zones of heavy orographic rainfall of typhoons over Taiwan, four forewarning zones models, including Taipei, Hsinee, Giashen and Hualian, were applied to this case study of typhoon Morakot. There are several different cross-sections of terrain which can be used to define the terrain in meso-scale the one windward side and the other lee side, and we can find out the wind directions which probably enhance the orographic effect and result in heavy rainfall. By using the image software, we can draw a map of typhoon circulation wind directions and make a typhoon wind directions board for each place where invaded by typhoons from various directions. According to the terrain cross-sections, we can also compose the terrain map to the typhoon wind directions board to check the windward side or the lee side and define the forewarning zones which probably cause heavy orographic rain when typhoon center enter into these specifi c windward side areas. In this study, the forewarning zones radius were set to 300kms to simulate the storm radius of typhoon Morakot circulation. The result of this research is confident. The regional difference of typhoon Morakot rainfall affected by terrain can be explained very well in this case study. Briefly, if we consider the meso-scale terrain effect, related to the macro-scale terrain of entire Taiwan, and consider the scope of the local forewarning regime, it will be more valid in typhoon rainfall forecast and more effective in disaster prevention.