Tropical Storm Sonca (2017)

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Saffir–Simpson scale
  Tropical depression (≤38 mph, ≤62 km/h)
  Tropical storm (39–73 mph, 63–118 km/h)
  Category 1 (74–95 mph, 119–153 km/h)
  Category 2 (96–110 mph, 154–177 km/h)
  Category 3 (111–129 mph, 178–208 km/h)
  Category 4 (130–156 mph, 209–251 km/h)
  Category 5 (≥157 mph, ≥252 km/h)
  Unknown
Storm type
Disc Plain black.svg Tropical cyclone
Solid black.svg Subtropical cyclone
ArrowUp.svg Extratropical cyclone, remnant low, tropical disturbance, or monsoon depression

On July 21, both the JMA and the JTWC reported that Tropical Depression 08W had developed approximately 582 km (361 mi) to the south of Hong Kong. [2] [3] The storm had a rapidly consolidating low-level circulation center. The storm had a marginally favorable environment, with slight improvement of poleward outflow. The JTWC later assessed that there was a likelihood for it to steadily intensify, but the peak intensity was uncertain, citing reasons such as poor initialization of the forecasting model and the small size of the tropical depression. [4] The storm's environment remained favorable the following day, with vertical windshear offset by poleward outflow; the JTWC did not change their prediction. [5] Early the next day, the JTWC designated the system as a tropical storm. [6] The system intensified into a tropical storm by JMA on July 23, [7] receiving the name Sonca. [6]

After 13 hours, the storm was pulled southward by a building northern steering ridge. Just before the storm had its peak intensity, the storm rapidly intensified after reports of a consolidating low-level circulation center. The storm later accelerated north after a steering ridge reoriented the storm. [8] By July 24, Sonca reached its maximum intensity with a minimum pressure of 994 hPa. [9] Early on July 25, the JTWC issued its final advisory as the system made landfall over in the Quảng Trị Province, Vietnam. [10] [11] The storm was downgraded into a tropical depression that same day by the JMA. The storm traversed northwest, eventually weakening inside Thailand. The storm dissipated on July 29. [12]

Preparations and impact

Vietnam

Warning for Tropical Storm Sonca issued for Vietnam. 20170724 TC SONCA.pdf
Warning for Tropical Storm Sonca issued for Vietnam.

During the storm, heavy floods were recorded in Vietnam, causing extensive property damage, submerging 229 villages. [13] A directive was sent to send firefighters and police to rescue people in the northern provinces of Vietnam. [14] Vietnam Airlines cancelled 11 flights to and from the Phu Bai International Airport while VietJet Air cancelled 16. [15] [16] Fishermen from Quảng Trị moved their boats away from the shore due to strong waves and winds. [17] The Nghệ An province banned all sea-related activities and ordered ships to return back to the shore. [18] Numerous houses and billboards were damaged from strong winds in the districts of Gio Linh and Vĩnh Linh. [19] Five spillways in the largest lake in Nghệ An, were opened. [20] Three national routes were flooded among four other provincial routes in Nghệ An. [21] At least six people were killed as of July 31, all in the provinces of Hà Tĩnh and Quảng Trị. Approximately 1,500 houses were damaged in these two provinces. Across multiple Vietnamese provinces, roughly 5,777 hectares (14,280 acres) of paddy fields and 750 hectares (1,900 acres) of croplands were damaged. [22] In Nghe An Province, the total damage caused by the storm exceeded 127 billion dong (US$5.6 million) as of July 28. [21] Total damage in Vietnam reached 300.7 billion dong (US$13 million). [23]

Cambodia

The Ministry of Water Resources and Meteorology warned everyone, especially fishermen and people at sea to avoid accidents during the storm. [24] Authorities issued a flood warning and "safety hills" were set up with shelter, food, and supplies. The Royal Cambodian Armed Forces deployed 350 soldiers to Preah Vihear to aid in relief efforts; a provincial official of the Kampong Thom province stated that the government was preparing to evacuate residents. The Steung Saen River reached a height of 13.4 metres (44 feet), close to emergency levels. Water levels at the Tamok Bridge rose 1 m (3.3 ft) above the average level. The governor of the Choam Khsant District stated that four communes in the district were flooded. [25] Tropical Storm Sonca, due to its heavy floods, affected four provinces across Cambodia, three people died, and 2,686 houses were submerged. 53 households, 550 affected families, and 1000 displaced residents were affected. [26] [27] Two of the deaths were caused by drowning. [25] In the Choam Khsant District, 48 families had to be evacuated because of the storm. [27]

Thailand

The hardest hit province was Sakon Nakhon, Northeast Thailand. [26] Damages in Sakon Nakhon exceeded 100 million baht (US$3 million). [28] The floods created by the storm were the strongest floods in the province in two decades. [29] Heavy rain damaged bridges in Khon Kaen province and flooded buildings in Ubon Ratchathani province and Sisaket province, where some people were relocated to temporary accommodations. In Lopburi province, some people were assisted into boats after the roads became impassable. In Sukhothai province, the Yom River flooded, and sandbags were used to help contain the floodwaters. Trains had to be re-routed in Nong Khai province when telephone poles fell on the tracks. [30] Villages in Chiang Rai were inundated due to the overflowing of a river on July 24. The next day, a flash flood occurred at the Den Chai district due to continuous rainfall. On July 26, rainfall caused the water level in the Phayao Lake to reach full capacity. Small cars struggled to pass roads in Kalasin due to flooding. Roads were destroyed in Khon Kaen while a landslide blocked a train tunnel in Chaiyaphum. A broken flood wall caused flooding in Sukhothai province. Flash flood occurred in eight provinces in Ranong while flooding also occurred in eight districts of Nakhon Ratchasima; the flooding in three were severe. [31] In total, the damage from flooding triggered by the storm in Thailand reached 10 billion baht (US$300 million). [32]

See also

Notes

  1. ↑ The name Sonca (Vietnamese: sơn ca, [səːn˧˧ kaː˧˧]) was contributed by Vietnam and refers to the Oriental skylark (Alauda gulgula) in Vietnamese. [1]
  2. ↑ 2017 USD.

References

  1. ↑ "List of names for tropical cyclones adopted by the Typhoon Committee for the western North Pacific and the South China Sea". Japan Meteorological Agency. Archived from the original on August 5, 2005. Retrieved April 25, 2026.
  2. ↑ "Marine Weather Warning for GMDSS Metarea XI 2017-07-21T06:00:00Z". WIS Portal – GISC Tokyo. Japan Meteorological Agency. Archived from the original on July 29, 2017. Retrieved July 21, 2017.
  3. ↑ "Tropical Depression 08W (Eight) Warning Nr 001". Joint Typhoon Warning Center. July 21, 2017. Archived from the original on May 23, 2024.
  4. ↑ "Prognostic Reasoning for Tropical Depression 08W (Eight) Warning NR 01". Joint Typhoon Warning Center. July 21, 2017. Archived from the original on July 23, 2017. Retrieved September 12, 2024.
  5. ↑ "Prognostic Reasoning for Tropical Depression 08W (Eight) Warning NR 05". Joint Typhoon Warning Center. July 22, 2024. Archived from the original on July 23, 2017. Retrieved September 12, 2024.
  6. 1 2 "Prognostic Reasoning for Tropical Storm 08W (Sonca) Warning No 10". Joint Typhoon Warning Center. July 23, 2017. Archived from the original on July 23, 2017. Retrieved October 13, 2024.
  7. ↑ "Tropical Storm 08W (Eight) Warning Nr 009". Joint Typhoon Warning Center. July 23, 2017. Archived from the original on May 23, 2024.
  8. ↑ "Prognostic Reasoning for Tropical Storm 08W (Sonca) Warning NR 13". Joint Typhoon Warning Center. July 14, 2017. Archived from the original on July 25, 2017. Retrieved September 14, 2024.
  9. ↑ "Tropical Storm 08W (Sonca) Warning Nr 016". Joint Typhoon Warning Center. July 24, 2017.{{cite web}}: CS1 maint: deprecated archival service (link)
  10. ↑ "Tropical Storm 08W (Sonca) Warning Nr 018". Joint Typhoon Warning Center. July 25, 2017.{{cite web}}: CS1 maint: deprecated archival service (link)
  11. ↑ "VIDEO Cập nhật bão số 4: Đổ bộ vào Quảng Trị và gây mưa lớn" [VIDEO Update about Typhoon No. 4: Makes landfall in Quảng Trị and causes heavy rain]. Thể thao & Văn hóa (in Vietnamese). Vietnam News Agency. July 25, 2017. Archived from the original on July 25, 2017. Retrieved August 5, 2017.
  12. ↑ "Typhoon Best Track 2017-09-05". Japan Meteorological Agency . September 5, 2017. Archived from the original on September 9, 2017. Retrieved September 13, 2025.
  13. ↑ Vn, Vietnam. Vnanet (August 3, 2017). "Thủ tướng gửi điện thăm hỏi tình hình lũ lụt tại Đông Bắc Thái Lan" [The Prime Minister sent a telegram to visit the flood situation in Northeast Thailand]. Báo Ảnh Việt Nam (in Vietnamese). Vietnam News Agency . Retrieved September 14, 2024. [It is reported that Typhoon Sonca has caused floods that caused great property damage in the northeastern provinces of Thailand, In Nakhon Ratchasima province, at least 229 villages in 5 districts have been submerged]
  14. ↑ Xuân Tùng (July 24, 2017). "Bộ Công an chỉ đạo lực lượng ứng phó với cơn bão số 4" [The Ministry of Public Security directs the force to respond to storm No. 4]. Báo Tin tức (in Vietnamese). Vietnam News Agency . Retrieved September 14, 2024. [On July 24, the Ministry of Public Security issued a telegram requesting the Police, Fire Prevention and Fighting Police of coastal provinces and cities from Quang Ninh to Da Nang and the Northern and North Central provinces to proactively deal with Typhoon No. 4]
  15. ↑ "Gần 30 chuyến bay bị hoãn do bão Sonca" [Nearly 30 flights delayed due to Typhoon Sonca]. VnExpress. July 25, 2017. Retrieved September 13, 2025.
  16. ↑ "Vietnam Airlines cancels 11 more flights due to storm". Vietnam+ (in Vietnamese). July 25, 2017. Retrieved April 1, 2026.
  17. ↑ "Ngư dân Quảng Trị đưa tàu thuyền vào bờ tránh bão" [Fishermen in Quang Tri bring boats to shore to avoid the storm]. VnExpress. July 25, 2017. Retrieved September 13, 2025.
  18. ↑ "Nghệ An cấm biển để chống bão Sonca" [Nghe An bans the sea to fight Typhoon Sonca]. VnExpress. July 24, 2017. Retrieved September 13, 2025.
  19. ↑ "Nhiều ngôi nhà bị tốc mái trong mưa bão ở Quảng Trị" [Many houses had their roofs blown off in rainstorms in Quang Tri]. VnExpress. July 25, 2017. Retrieved September 13, 2025.
  20. ↑ "Hồ lớn nhất tỉnh Nghệ An xả nước" [The largest lake in Nghe An province discharges water]. VnExpress. July 25, 2017. Retrieved September 13, 2025.
  21. 1 2 Thanh Huyền (July 28, 2017). "Nghệ An: Bão số 4 gây thiệt hại trên 127 tỷ đồng" [Nghe An: Typhoon No. 4 caused over 127 billion dong in damage]. Đài Phát thanh – Truyền hình Nghệ An (in Vietnamese). Archived from the original on April 2, 2019. Retrieved September 21, 2024.
  22. ↑ "Viet Nam, the Impact of Tropical Storm "Sonca"". ReliefWeb. United Nations Office for the Coordination of Humanitarian Affairs. July 31, 2017. Archived from the original on August 15, 2017. Retrieved September 21, 2024.
  23. ↑ "Tổng hợp thiệt hại do thiên tai năm 2017" [Total damages from natural disasters in 2017](PDF) (in Vietnamese). Vietnamese Ministry of Agriculture and Rural Development. Archived from the original (PDF) on March 31, 2020. Retrieved March 21, 2024.
  24. ↑ Kunthear, Mom (July 25, 2017). "Tropical storm promises downpour". Khmer Times . Retrieved September 14, 2024.
  25. 1 2 Pheap, Aun (July 28, 2017). "Authorities Ready for Tropical Storm 'Sonca' Flood Evacuations - The Cambodia Daily". The Cambodia Daily. Archived from the original on May 25, 2022. Retrieved September 13, 2025.
  26. 1 2 "AHA Centre Flash Update: Flooding, Cambodia, Lao PDR, Myanmar & Thailand". ReliefWeb. United Nations Office for the Coordination of Humanitarian Affairs. August 2, 2017. Archived from the original on August 2, 2017. Retrieved August 5, 2017.
  27. 1 2 "Cambodia, The Impact of Tropical Storm "Sonca"". ReliefWeb. United Nations Office for the Coordination of Humanitarian Affairs. July 28, 2017. Archived from the original on September 21, 2024. Retrieved September 14, 2024.
  28. ↑ "Sakon Nakhon flood damage estimated at over Bt100 million". The Nation. July 29, 2017. Archived from the original on September 3, 2017. Retrieved August 5, 2017.
  29. ↑ "King urges quick relief after floods". Bangkok Post. July 31, 2017. Archived from the original on August 3, 2017. Retrieved September 21, 2024.
  30. ↑ "Flooding worsens as Sonca influence intensifies". Pattaya Mail. July 29, 2017. Archived from the original on August 13, 2017. Retrieved August 14, 2017.
  31. ↑ Prutthiprasert, Sutiwat (August 3, 2017). "Sonca Storm in Thailand". InterRisk Asia (Thailand) Co., Ltd. Retrieved September 13, 2025.
  32. ↑ "Thailand floods kill 23, cause damage estimated at $300 million". Reuters . August 3, 2017. Archived from the original on September 25, 2017. Retrieved September 21, 2024.
Tropical Storm Sonca
Sonca 2017-07-25 0630Z.jpg
Sonca nearing landfall on July 25
Tropical cyclones of the 2017 Pacific typhoon season
2017 Pacific typhoon season summary.png
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Crising
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Nanmadol
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Talas
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Sonca
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26W
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29W
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