page_title: Tropical Storm Son-Tinh (2018)
section_title: Meteorological history
hierarchical_section_title: Tropical Storm Son-Tinh (2018) / Meteorological history
caption_attribution_description: English: Track map of Tropical Storm Son-Tinh of the 2018 Pacific typhoon season. The points show the location of the storm at 6-hour intervals. The colour represents the storm's maximum sustained wind speeds as classified in the Saffir–Simpson scale (see below), and the shape of the data points represent the nature of the storm, according to the legend below. Saffir–Simpson scale Tropical depression≤38 mph≤62 km/h Category 3111–129 mph178–208 km/h Tropical storm39–73 mph63–118 km/h Category 4130–156 mph209–251 km/h Category 174–95 mph119–153 km/h Category 5≥157 mph≥252 km/h Category 296–110 mph154–177 km/h Unknown Storm type Tropical cyclone Subtropical cyclone Extratropical cyclone / Remnant low / Tropical disturbance / Monsoon depression
context_page_description: Tropical Storm Son-Tinh, known in the Philippines as Tropical Storm Henry, was a weak but very deadly tropical cyclone that devastated Vietnam and Laos in July 2018. Son-Tinh originated from an area of low pressure over the Philippine Sea on July 15, 2018. Moving quickly westwards, Son-Tinh strengthened to the ninth tropical storm of the annual typhoon season on July 17. Intensifying only slightly while crossing the South China Sea, Son-Tinh made its first landfall over Hainan Island on July 18. After emerging into the Gulf of Tonkin, Son-Tinh restrengthened before making its second landfall as a tropical storm in Northern Vietnam on July 19. Once inland, Son-Tinh weakened into a low pressure area as it slowed and made a clockwise loop. The remnants of Son-Tinh then emerged back over water and regenerated into a tropical depression late on July 21.
  The storm caused severe floods and mudslides in Vietnam, leading to the death of at least 32 people. Over 82,000 hectares of agricultural land was inundated and at least 17,000 farm animals were swept away by the floods.
context_section_description: An area of low pressure strengthened into a tropical depression on July 15, to the northwest of Manila, Philippines. Accordingly, the Joint Typhoon Warning Center (JTWC) designated it as 11W while the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) gave it the local name Henry. As the system moved westward at high speed, it gradually intensified as its convective structure improved, and strengthened a tropical storm by July 17, with the Japan Meteorological Agency (JMA) assigning the system the international name Son-Tinh.
  Thereafter, however, Son-Tinh weakened slightly as it neared Hainan island due to moderate vertical wind shear. Continuing to struggle to maintain intensity amid increasing wind shear, Son-Tinh crossed over Hainan island at around 03:00 UTC on July 18; despite land interaction the system continued to maintain its overall convective organization. Later that day, as Son-Tinh emerged from land into the Gulf of Tonkin, Son-Tinh managed to intensify over the warm waters, with sea surface temperatures of over 28 °C (82 °F) contributing to offset otherwise unfavorable upper atmospheric conditions. Before making landfall in Northern Vietnam, the JMA reported that Son-Tinh reached peak intensity with 10-minute sustained winds of 75 km/h (45 mph) and a central pressure of 994 hPa (29.4 inHg). Once inland over Northern Vietnam, Son-Tinh began to weaken quickly. Both the JMA, RFE and JTWC issued their final warnings on Son-Tinh on July 19 as the system degenerated into an area of low pressure embedded in the monsoon. The JTWC, however, continued to track Son-Tinh's remnants for the next two days.
  Through July 19 and 20, Son-Tinh's remnants curved northwards and then eastwards over Northern Vietnam, before moving southeastward back into the Gulf of Tonkin on July 21. Persistent convection developed over the system, aided by a tropical upper tropospheric trough to the northeast, prompting the JTWC to begin issuing advisories on Son-Tinh once again on July 21. Simultaneously the JMA reported that Son-Tinh had regenerated into a tropical depression. With vertical wind shear now low and sea surface temperatures remaining high near 29 °C (84 °F), the JTWC stated that Son-Tinh intensified back into a tropical storm on July 22, while the JMA continued to maintain Son-Tinh as a tropical depression.
caption: Map plotting the track and the intensity of the storm, according to the Saffir–Simpson scale
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