# Elliptical Structures of Gravity Waves Produced by Typhoon Soudelor in 2015 near Taiwan
## 3 Overview of TC Soudelor and Model Validation  
### Tropical Cyclone Soudelor (2015)  
Tropical cyclone Soudelor was the most powerful TC in the 2015 Pacific typhoon season. It was formed near Pohnpei (6.8\({}^{\circ}\) N, 158.2\({}^{\circ}\) E) in the north-central tropical Pacific on 29 July 2015. Soudelor was classified as a Category 1 TC (V\({}_{\rm max}\) \(<\) 33 m/s) on the Saffir-Simpson hurricane wind scale on 31 July 2015. It underwent rapid intensification on 2 August 2015 and made landfall on Saipan (15.2\({}^{\circ}\) N, 147.5\({}^{\circ}\) E) in the Northern Mariana Islands on 3 August. The intensity increased to Category 5 (V\({}_{\rm max}\)\(>\) 70 m/s) at 15:00 UTC on Monday, 3 August. The 10 min (1 min) maximum sustained winds and minimum central pressure peaked at about 60 m/s (80 m/s) and 910 hPa, respectively (Figure 2a). Soudelor underwent an eyewall replacement cycle (ERC) with steady weakening from 4 August until its re-intensification above warmer waters with SST and OHC values \(>\) 30 \({}^{\circ}\)C and 75 kJ/cm\({}^{2}\), respectively (refer to the Regional and Mesoscale Meteorology Branch products), at longitudes between 124\({}^{\circ}\) E and 126\({}^{\circ}\) E when it was approaching Taiwan late on 6 August. At 03:00 UTC on Friday, 7 August, the intense TC reached 1 min maximum sustained winds of about 50 m/s with wind gusts around 67 m/s when moving west-north-west at a speed of 5.1 m/s toward Taiwan (24\({}^{\circ}\) N, 121.6\({}^{\circ}\) E). A second ERC was undergone during the re-intensification stage from 6 August before the Category 3 TC (V\({}_{\rm max}\)\(<\) 50 m/s) landfall over Xiulin, Hualien in Taiwan at 20:40 UTC (04:40 LST on 8 August). Indeed, the World Wide Lightning Location Network Tropical Cyclone (WWLLN-TC) observations supported the occurrence of an ERC with peaks of lightning strokes within 100 km (1000 km) of the TC center on 3 August (6 August). After crossing the Taiwan Strait from Taixi, Yunlin in Taiwan, the Category 1 TC made a new landfall over Mainland China around 14:10 UTC on 8 August and quickly downgraded inland from 9 August. It totally dissipated near Jeju Island (33.5\({}^{\circ}\) N, 126.5\({}^{\circ}\) E) on 13 August. The Central Mountain Range (CMR), with an average elevation of about 2000 m, modified the TC track [51; 52; 53] causing a slight northward deflection prior to landfall and a fairly substantial southward deflection from 8 August 00:00 UTC above the CMR. It also caused a north-west deflection after 06:00 UTC (Figure 1a). About 31% of the landfall typhoon pathways over Taiwan from 1981 to 2015 were similar to the one of TC Soudelor [54]. Heavy rains were unleashed from late on 6 August until early on 8 August, when the TC was above the Taiwan Strait (Figure 2b). A rainfall asymmetry was observed on the right side of the TC over warmer waters on 7 August. Radar observation visualized the time evolution of the surface TC structure, such as the breakdown of the inner core (Figure 3), as a response to the landfall over the island and the formation of a mesoscale secondary low center on the lee side of the southern CMR at about 23:10 UTC. The circular central core became elongated near the eastern Taiwanese coast accompanied by extremely heavy rain funneling into the far north of Taiwan. Meteorological stations reported light rain \(<\) 2.5 mm/h at Hualien (24\({}^{\circ}\) N, 121.6\({}^{\circ}\) E) at 12:00 UTC on 7 August and violent rain of 53.5 mm/h at 22:00 UTC on 7 August. When the mesoscale's low center was formed, precipitation decreased quickly in Northern Taiwan to increase in the southern part (see Figure 4 in reference [55]). Large maximum 24 h rainfall of 1042 mm was observed from 7 July 12:00 UTC to 8 July 12:00 UTC over Northern Taiwan during TC Soudelor. Figure 3: _Cont._  
Figure 2: **(a)** Time evolution of minimum central pressure (black) and 1 min sustained wind (red) of TC Soudelor from 30 July 2015 00:00 UTC to 9 August 2015 12:00 UTC, derived from best track observations.