Severe Tropical Storm Talas was a tropical cyclone that affected Vietnam in mid-July 2017. The storm was first identified as a tropical disturbance over the South China Sea on July 13 and was upgraded to a tropical depression the following day. On July 15, the depression intensified into a named storm of the 2017 Pacific typhoon season. Before making landfall in Vietnam, Talas reached its peak intensity as a severe tropical storm on July 16. It weakened to an area of low pressure on July 17 as it moved inland. Throughout Vietnam, the storm resulted in 14 fatalities and damaged approximately 2,700 homes. Rough seas caused about 50 boats to sink. Nearly of vegetable fields, around of aquaculture, and of rice and other subsidiary crops were affected. The storm caused an estimated US$8.8 million in damages in Hainan, China, increased rainfall in Myanmar and Thailand, and triggered landslides and flooding in parts of Central and Northern Laos.
Talas originated from an area of convection, positioned between two north-south oriented ridges. On July 13, the Joint Typhoon Warning Center (JTWC) began monitoring a tropical disturbance located approximately southeast of Hanoi, Vietnam. The Japan Meteorological Agency (JMA) classified the system as a weak tropical depression at around 06:00 UTC on July 14, as it started to move slowly towards the northwest at a speed of . Six hours later, the JMA issued advisories stating that the system was producing 10-minute sustained winds of at least . The JMA then upgraded it to a tropical storm, assigning it the name Talas.
The JTWC issued a Tropical Cyclone Formation Alert at 02:30 UTC on July 15, after satellite imagery depicted deep convection wrapping into its developing low-level circulation center and a favorable environment for further development in Hainan, China. As convective banding improved, the JTWC downgraded the disturbance to a tropical depression by midday on July 15. The JTWC upgraded it to a tropical storm after recording Dvorak estimates of T2.5, indicating 1-minute sustained winds of .
On July 16, Talas gradually intensified as it became better organized due to a favorable environment consisting of low to moderate northeasterly vertical wind shear and good outflow to the south. At 09:00 UTC, the JMA upgraded the storm to a severe tropical storm after it attained 10-minute sustained winds of and a minimum barometric pressure of , reaching its peak intensity. At the same time, the JTWC recorded one-minute sustained peak winds of while trailing along Hainan.
Shortly thereafter, Talas began to weaken due to land interaction and the JMA downgraded the system back to a tropical storm. Around 18:00 UTC, the storm made landfall in Central Vietnam, near the city of Vinh. Three hours later, the JTWC issued their final advisory on Talas as it continued to degrade while progressing inland. Early in the following day, when the weakening storm was located over the northern portion of Laos, the JMA issued their final advisory as well.
On July 15, meteorologists expected heavy rainfall from Talas. The storm made landfall near Vinh at around 18:00 UTC on July 16 as a moderate tropical storm. Vietnam's National Center for Hydro-Meteorological Forecasting recorded wind gusts up to , causing damage in NghỠAn, Thanh Hóa and HàTénh provinces. Over of rain fell in the central and northern parts of the country in the two days before landfall, while the capital, Hanoi, received .
Talas caused 14 deaths; damaged around 3,000 homes; and sank 50 boats. Power lines in three provinces were damaged as a result of the storm. The storm destroyed approximately of vegetable fields, of aquaculture farms, and of rice and subsidiary crops were. The storm resulted in approximately (approximately US$70.4 million). The total cost of other damages was estimated at (US$109 million). Damages in Nghá» An were reported to reach up to (approximately US$43.7 million).
The storm sank a coal ship late on July 16; only three of the thirteen people on board were rescued. Seven people were injured in Quảng Bình province, where fishing boats also washed ashore on waves as high as . The national guard rescued a boat carrying eight weather officials after the storm. On July 17, flooded streets and disrupted train services stranded more than 4,000 passengers in the capital. Railway services from Hanoi to Vinh were canceled while trains from Hanoi to Saigon were delayed by five to seven hours. The storm caused multiple severe traffic jams, and capsized a ship, injuring seven people. Eight flights were cancelled by the airline VietJet Air and other airlines cancelled an additional ten. In response to the storm, the Irrigation Department ordered every district to have an irrigation office and/or adding pumps.
On July 22, China's National Observatory issued a "blue alert" to Hainan province and the Beibu Gulf. About 22,901 fishing boats were moved and 39,425 people working at sea farms were evacuated to Guangdong province. As the storm neared the coast, winds of were recorded around the Lingshui Li Autonomous County. Southern portions of the province received rainfall of and tourists were stranded on a remote island off the coast of Guangdong. Total economic losses in Hainan Province reached (approximately US$3.5 million) and (approximately US$8.8 million) in China overall.
Laos, Myanmar and Thailand received strong winds and heavy rains. Rainfall increased in Thailand between 15 and 18 July, reaching a peak of on 17 July in the Phu Phiang district of Nan province. Three districts flooded as a result of rivers overflowing in Nan province, including the Nan River. The storm passed over the Laotian provinces of Xiangkhouang, Xaysomboun and Bolikhamsai early in the morning of 17 July. On that and the following day, the rain caused landslides and flash floods in areas of Central and Northern Laos.