Journal of Geoscience and Environment Protection, 2017, 5, 235-251 http://www.scirp.org/journal/gep ISSN Online: 2327-4344 ISSN Print: 2327-4336 Analysis of Special Strong Wind and Severe Rainstorm Caused by Typhoon Rammasun in Guangxi, China Xiakun Zhang1, Jian Chen2*, Zhenquan Lai2, Liping Zhai2, Mo Lin3 1National Meteorological Center of CMA, Beijing, China 2Guangxi Meteorological Observatory, Nanning, China 3Guangxi Meteorological Disaster Mitigation Institute, Nanning, China How to cite this paper: Zhang, X.K., Chen, Abstract J., Lai, Z.Q., Zhai, L.P. and Lin, M. (2017) Analysis of Special Strong Wind and Severe Based on conventional meteorological observation data, NCEP 1˚ × 1˚ reana- Rainstorm Caused by Typhoon Rammasun lysis data, reanalysis data with resolution 0.75˚ × 0.75˚ from ECMWF and in Guangxi, China. Journal of Geoscience Doppler weather radar, we analyzed the weather conditions and physical cha- and Environment Protection, 5, 235-251. racteristics of Super Typhoon Rammasun (1409), which caused special strong https://doi.org/10.4236/gep.2017.58019 wind and severe rainstorm in Guangxi. The results show that: 1) Typhoon Received: December 30, 2016 Rammasun offshore sudden strengthening in one of the main reasons was Accepted: August 7, 2017 that loop pressure ridge superimposed into the westward extension of sub- Published: August 10, 2017 tropical high, to making enable rapid strengthening of the subtropical high, so the subtropical high advanced faster than the Rammasun move, Rammasun Copyright © 2017 by authors and Scientific Research Publishing Inc. center of the subtropical high distance reduced and the gradient increased; 2) This work is licensed under the Creative Rammasun northward to south china coast with plenty of vapor following Commons Attribution International ITCZ, before landing, southwest monsoon and cross-equatorial flow were in- License (CC BY 4.0). volved, Rammasun got latent heat of monsoon jet, enabling it to strengthen in http://creativecommons.org/licenses/by/4.0/ offshore; 3) Rammasun from the Qiongzhou Strait into the northern Gulf, Open Access therefore the Strait of short passages and both sides belong to the low zone, friction consumption smaller, that was the main reason what was able to maintain the strength of the super typhoon, when Rammasun into the Beibu Gulf; 4) Diagnostic analysis shows that Rammasun before entering the north- ern Gulf and into the Beibu Gulf later, vorticity weakened, divergence and vapor flux divergence changed were smaller, meanwhile, vertical ascent speed and latent heat transport both increased, which was important reason of se- vere rainstorm caused by Rammasun. Keywords Typhoon Rammasun, Strong Wind, Severe Rainstorm, Cause Analysis, Guangxi DOI: 10.4236/gep.2017.58019 Aug. 10, 2017 235 Journal of Geoscience and Environment Protection X. K. Zhang et al. 1. Introduction The typhoon “Rammasun” (super typhoon level) is one of the major disaster weather events that seriously affected South China. Due to its influence, the strong winds and severe torrential rains in Hainan, Guangdong and Guangxi caused significant personnel casualties and property losses, to achieve large-scale meteorological disaster levels. The “Rammasun” before landing in Wenchang of Hainan province, suddenly increase in strength, from 10:00 on July 17. The cen- tral intensity of 35,970 continued to strengthen to July 18, 14:00 center strength 60,915. Landing in Xuwen of Guangdong province, at 20:00 on July 20, the “Rammasun” enhanced to the central intensity of 60,910. Into the northern Gulf of the sea, the intensity has weakened. At 19:00 on July 19, the center strength of 52,935, down to 16 from 17. Compared with the intensity of the Gulf of Tonkin significantly weakened into difference of strong typhoon in previous years through Hainan Island or Leizhou Peninsula, with the “Rammasun” landing the North Bay, the wind speed is very small, still maintain a super typhoon intensity. So with the third landing Fangchenggang in Guangxi, the center of the wind is still 15, and accompanied by heavy rain. Winds set off coastal waves, resulting in coastal aquaculture facilities and marine products suffered devastating damage. After verification, the “Rammasun”, strong winds with the destructive power, is the strongest typhoon records since the weather records in 1949 in Guangxi. Due to the intensity of the “Rammasun” and the extreme nature of the disaster, it is necessary to analyze the reason why the intensity of the anomaly increases sud- denly in the coastal waters and reaches the super-intensity level after entering the northern Gulf, so as to provide reference for future similar process forecast. In the past studies, it is generally believed that the change of typhoon intensity mainly depends on the three factors of ambient airflow, typhoon structure and ocean condition (Duan Yihong, et al., 2005) [1]. The rapid intensification of tropical cyclones in the coastal waters of South China occurred mainly in the east-west-low-type, north-high-south-type and weak-background conditions (Lin Liangxun, et al., 2006) [2]. In the three circulation regimes, the intensifica- tion of the southwest monsoon and the transport to the northern South China Sea, the northward of the cross-equatorial current, the westward transmission of the easterly waves, the invasion of weak cold air and the induction of the short wave channel of the westerly wind are all closely related to the enhancement of tropical cyclones. And the rapid increase of TC induced by southwest monsoon was the most common. Kong Ningqian, et al. (2007) [3] conducted a statistical analysis of tropical cyclones active in the central and northern South China Sea during 1960-2002, and summarized the climatic characteristics of TC intensity abrupt change in the central and northern SCS. It is pointed out that the major weather systems affecting tropical cyclone intensity variation are the subtropical high, the tropical convergence zone, the southwest monsoon trough, the wester- ly trough and the typhoon. And the subtropical high is the most frequent. Hu Chunmei, et al. (2005) [4] analyzed large-scale TCs of two types of TCs, which DOI: 10.4236/gep.2017.58019 236 Journal of Geoscience and Environment Protection X. K. Zhang et al. were rapidly weakened and rapidly strengthened before landfall in South China. It was concluded that low-level convergence and high-level divergence of TC were strong and it had sufficient water vapor. These research results have im- portant significance of guiding to judge whether typhoon is strengthened in South China coastal waters. The analysis of the “Rammasun” shows that its movement is in the background of low circulation, and the intensification of the subtropical high, the southwest monsoon and the cross-equatorial air entrain- ment are the important reasons for the sudden intensification of the offshore in- tensity. And through the low zone of Qiongzhou Strait into the northern Gulf is an important reason to maintain its strength at super-level. In this paper, we use the conventional meteorological data, the NCEP 1.0˚ × 1.0˚ reanalysis data and the European high resolution reanalysis data (0.75˚ × 0.75˚) to analyze the cause of heavy rain and weather and dynamic diagnostic caused by the “Rammasun”, which will accumulate the experience for the typhoon forecast. Strengthening typhoon monitoring and forecasting is an important measure to reduce typhoon disaster. The detection of typhoons mainly uses meteorologi- cal satellites. In the satellite cloud, you can clearly see the presence and size of the typhoon. The use of meteorological satellite data to determine the location of the typhoon center, the estimated typhoon intensity, monitoring the direction, speed of typhoon movement, the emergence of storms and other areas, to pre- vent and mitigate the typhoon disaster plays a key role. When the typhoon ar- rived in the sea, the radar can also be used to monitor the typhoon. The estab- lishment of the city’s early warning system improves the emergency response capability and the establishment of emergency response mechanism. There are also weather forecasters, according to the various information obtained, the analysis of the trend of typhoons and the landing location and time, timely re- lease of typhoon forecasts and typhoons or emergency warning, through televi- sion, radio and other media for the public service, fishing vessels in time to shel- ter, at the same time for all levels of government to provide decision-making ba- sis, the release of typhoon forecast or alarm is an important measure to reduce typhoon disaster. 2. An Overview of Typhoon The “Rammasun” generated in the north-west Pacific on July 12, 2014, and landed in the central coast of the Philippines in evening on July 15, and became the super typhoon in the South China Sea at 5:00 on July 18. At 18:30 on July 18, landing in Wengtian Town, Wenchang City, Hainan Province, the maximum wind speed near the center of the landing is 60 m/s (17 levels). At 18:30 on July 18 landing in Long Town coastal, Xuwen County, Guangdong Province with the same intensity once again. At 7:00 on July 19 third landing in Guangpo town coast, Fangchenggang City, Guangxi province, the maximum wind speed near the center of landing is 48 m/s (15, strong typhoon level). After landing, it went by Gang Kouqu and Fang Chengqu in Fang Chenggang City of Guangxi prov- ince (Weakened to Typhoon level), Shangsi County, Ningming County in DOI: 10.4236/gep.2017.58019 237 Journal of Geoscience and Environment Protection X. K. Zhang et al. Chongming City, Longzhou County (weakened to a strong tropical storm lev- el), finally into the northern Vietnam (Figure 1(a)). In this paper, convention- al meteorological data from China Meteorological Data Network, combined with mesoscale automatic station monitoring data, then we get Figure 1 through analysing these data.