Tropical Storm Son-Tinh (2018)

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.

Tropical Storm Son-Tinh (Henry)
Tropical storm (JMA scale)
Tropical storm (SSHWS)
Tropical Storm Son-Tinh nearing Vietnam on July 18
FormedJuly 15, 2018
DissipatedJuly 24, 2018
Highest winds10-minute sustained: 75 km/h (45 mph)
1-minute sustained: 85 km/h (50 mph)
Lowest pressure994 hPa (mbar); 29.35 inHg
Fatalities173 total, possibly 1,100 more are missing [1]
Damage$323 million (2018 USD)
Areas affectedPhilippines, South China, Vietnam, Laos, Thailand, Myanmar
Part of the 2018 Pacific typhoon season

The storm caused severe floods and mudslides in Vietnam, leading to the death of at least 32 people.[2][3][4] Over 82,000 hectares (200,000 acres) of agricultural land was inundated and at least 17,000 farm animals were swept away by the floods. The storm also caused or related to the havoc in the neighbouring country of Laos with the collapse of Attapeu dam, in which 40 people died and 98 more missing (and probably as much as 1,100 more people are missing[1]) and 6,600 more are displaced.[5][6][7]

Meteorological history
Map plotting the track and the intensity of the storm, according to the Saffir–Simpson scale

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.[8][9] 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.[10][11]

Thereafter, however, Son-Tinh weakened slightly as it neared Hainan island due to moderate vertical wind shear.[12] 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.[13] 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.[14] 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).[15] 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.[16][17] The JTWC, however, continued to track Son-Tinh's remnants for the next two days.[18]

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.[18] 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.[19] Simultaneously the JMA reported that Son-Tinh had regenerated into a tropical depression.[20] 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,[21] while the JMA continued to maintain Son-Tinh as a tropical depression.[22]

Preparations and impact

China

Total economic loss nationwide were at ¥240 million (US$35.7 million).[23]

Vietnam
Main article: 2018 Northern Vietnam floods

On July 18, the Vietnamese government ordered all vessels to return to port.[24]

In Vietnam, the Thanh Hóa and Nghệ An provinces suffered the most damage, especially with the wake of the storm continuing to generate significant rainfall.[25] It caused major flooding in Northern Vietnam and the capital city of Hanoi.[3] 35 people were killed, more than 5,000 houses, 82,000 hectares (200,000 acres) of crops, and 17,000 farm animals were either swept away, submerged, or otherwise destroyed.[3] The storm has cut off access to several areas in the country and flood water covers several streets in the capital city.[25] Economic losses were estimated to be ₫6.615 trillion (US$287 million).[26]

Laos
Main article: 2018 Laos dam collapse

On July 23, a hydroelectric dam under construction in Attapeu Province, south-east Laos, collapsed. As of September 25, 40 people were confirmed dead,[5] at least 98 more were missing (and probably as much as 1,100 more people are missing[1]) and 6,600 others were displaced.[6][7]

See also

References
  1. "Laos struggles to find missing after dam collapse". Al Jazeera. July 29, 2018. Retrieved June 11, 2020.
  2. "Vietnam flood death toll rises to 27, more rain forecast".
  3. Nguyen, Mai (July 21, 2018). "Storm Son Tinh kills 20, leaves 16 missing in Vietnam". U.S. Retrieved July 22, 2018.
  4. Sidhu, Sandi; Cullinane, Susannah (July 22, 2018). "Storms, landslides and heat hit Asia". CNN. Retrieved July 22, 2018.
  5. Ferrie 2018.
  6. Al Jazeera 2018.
  7. Channel News Asia 2018.
  8. "Tropical Depression 11W (Eleven) Warning Nr 01". Joint Typhoon Warning Center. July 15, 2018. Archived from the original on July 15, 2018.
  9. "Severe Weather Bulletin #1 For Tropical Depression Henry". Philippine Atmospheric, Geophysical and Astronomical Services Administration. July 15, 2018. Archived from the original (PDF) on July 15, 2018. Retrieved July 23, 2018.
  10. "Prognostic Reasoning for Tropical Storm 11W (Son-Tinh) Warning Nr 07". Joint Typhoon Warning Center. July 17, 2018. Archived from the original on July 17, 2018.
  11. "TS 1809 SON-TINH (1809) UPGRADED FROM TD". Japan Meteorological Agency. July 17, 2018. Archived from the original on July 17, 2018. Retrieved July 23, 2018.
  12. "Prognostic Reasoning for Tropical Storm 11W (Son-Tinh) Warning Nr 08". Joint Typhoon Warning Center. July 17, 2018. Archived from the original on July 17, 2018.
  13. "Prognostic Reasoning for Tropical Storm 11W (Son-Tinh) Warning Nr 10". Joint Typhoon Warning Center. July 18, 2018. Archived from the original on July 18, 2018. Retrieved July 23, 2018.
  14. "Prognostic Reasoning for Tropical Storm 11W (Son-Tinh) Warning Nr 12". Joint Typhoon Warning Center. July 18, 2018. Archived from the original on July 18, 2018. Retrieved July 23, 2018.
  15. "TS 1809 SON-TINH (1809)". Japan Meteorological Agency. July 18, 2018. Archived from the original on July 18, 2018. Retrieved July 23, 2018.
  16. "Tropical Storm 11W (Son-Tinh) Warning Nr 014". Joint Typhoon Warning Center. July 19, 2018. Archived from the original on July 19, 2018.
  17. "TD DOWNGRADED FROM TS 1809 SON-TINH (1809)". Japan Meteorological Agency. July 19, 2018. Archived from the original on July 19, 2018. Retrieved July 23, 2018.
  18. "Tracking data". National Oceanic and Atmospheric Administration. July 22, 2018. Retrieved July 22, 2018.
  19. "Prognostic Reasoning for Tropical Depression 11W (Son-Tinh) Warning Nr 15". Joint Typhoon Warning Center. July 21, 2018. Archived from the original on July 23, 2018. Retrieved July 23, 2018.
  20. "WARNING AND SUMMARY 210600". Japan Meteorological Agency. July 21, 2018. Archived from the original on July 21, 2018. Retrieved July 23, 2018.
  21. "Prognostic Reasoning for Tropical Storm 11W (Son-Tinh) Warning Nr 18". Joint Typhoon Warning Center. July 22, 2018. Archived from the original on July 23, 2018. Retrieved July 23, 2018.
  22. "WARNING AND SUMMARY 220000". Japan Meteorological Agency. July 22, 2018. Archived from the original on July 22, 2018. Retrieved July 23, 2018.
  23. CMA (December 4, 2018). Member Report: China (PDF). ESCAP/WMO Typhoon Committee. ESCAP/WMO Typhoon Committee. pp. 1–2. Archived from the original (PDF) on December 4, 2018. Retrieved December 4, 2018.
  24. Vu, Khanh (July 18, 2018). "Vietnam orders vessels back to port, braces for Son Tinh tropical". Reuters. Retrieved July 22, 2018.
  25. "At least 10 dead in Vietnam floods triggered by Typhoon Son Tinh". The New Indian Express. PTI. July 21, 2018. Retrieved July 22, 2018.
  26. "Tóm tắt các cơn bão trong năm 2018" (in Vietnamese). Government of Tuyen Quang province. January 5, 2019. Retrieved January 20, 2019.
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