Extended Abstract

3. Contributions of the east-west oriented convective bandChuang and Wei (2010) used the C-band dual-polarization r adar in Makung,Taiwan and the S-band Doppler weather r adar in Qigu to analyze the kinematicstructure of the convective cells in Typhoon Morakot during 2200 UTC 8 August to 0600UTC 9 August. A linear rainband oriented east-west existed in the vicinity of the Taiwanwest coas t with a significant confluen ce between the wester ly flow and thesouthwesterly flow. The dual- Doppler r adar wind analys is documented a jet-likewesterly flow between 2 km and 5 km with a maxim um exceeding 24 m s -1 that wasassociated with the east-west rainband. New c ells developed upst ream of theconfluence line and propagated westward inland toward the CMR.Wang et. al. (2010) utilize d the entire Taiwan we ather radar network of sixDoppler radars and f our dual polarization r adars during five stages of the Morakotpassage: (1) Approach to Taiwan; (2) Slow movement; (3) Landfall; (4) Typhoon cente rin Taiwan Strait; and (5) Approach to Fujian Province. From the radar analyses of Tang(2010), strong east-west oriented rainband s repeatedly formed during stage (4) nearsouthwestern Taiwan along the c onvergence zone between the typhoon circulation andthe southwesterly monsoon flow (Fig. 2). Notice the east-west band designated D3 inFig. 2a that extends from over the Taiwan Strait at the edge of the radar coverage to theregion of the southern CMR where the landslide occurred. Individual convect ive cells inthe bands are shown in the horizontal radar re flectivity depiction at 4 km at 1600 LST 8August 2009 (Fig. 2b). The curvature of the ra inband suggests it is related to the outercirculation of Typhoon Mora kot and that deep conv ective cells are beginning at thewestern end and grow as they propagate along the band toward the coast. These deepconvective towers persisted for about two hours and moved rapidly toward the island. Anorth-south cross-section throug h one of t he conv ective cells (not shown) indicates astrong updraft on the north side (s ide toward typhoon center) with a strong downdraft inthe mid-troposphere on t he south side. At this time, t he strongest low-level relativeinflow to the band was from t he south. The corresponding v ertical cross-section of thewind speeds indicates the deep c onvective cell was on the southern boundary of a lowleveljet with speeds of 35-45 m s-1 . Clearly, this low-level jet was transporting largeamounts of water vapor toward the west co ast of Taiwan and the southern CMR, andthis was contributing to the extreme precipitation.Although these rainbands generally propagated southward, the majordevastating rainband oscillated between 22.5°N and 23.5°N, as indicated in theHovmoller diagram in Fig. 3. T his osc illatory motion of the rainband appeared to berelated to a reversal in the relative strengt h of the low-level inflow from the south andthen from the north. These radar studies provide conclusive evidence of the convectivecells that build in the convergence lin e between the typhoon circulation and thesouthwesterly monsoon winds, and that the eas t-west orientation of this rainbanddirected the convective cells toward the CMR.-61-