September 2009 Vietnam tropical depression

Meteorological history

The tropical depression originated from an area of low pressure in the South China Sea on September 1. Scattered convection was associated with the system, with the center devoid of showers and thunderstorms, as the low slowly tracked westward in a weak steering environment. Weak outflow had formed along the northern edge of the system; however, intensification was not anticipated. The following day, convection began to form around the center of circulation and weak diffluence was noted around the system due to an anticyclone to the north. With low wind shear, convective banding features began to develop and the possibility of the system becoming a tropical cyclone increased. Early on September 3, the JMA began issuing advisories on the cyclone, classifying it as a tropical depression, the twentieth depression to be monitored by the JMA during the season.

Although the system had a partially exposed low-level circulation center, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert (TCFA) as the depression was likely to intensify as it was situated over high sea surface temperatures and in a favorable environment. However, by September 4, wind shear quickly increased and dislocated all of the convection associated with the depression from the center of circulation. This led to the JTWC canceling their TCFA as the environment was no longer favorable for development. The following day, the JTWC declared that the system had dissipated and was no longer a suspect area for tropical cyclone development as the system was virtually stationary off the coast of Vietnam. The JMA, on the other hand, continued to monitor the cyclone as a tropical depression. Although previously declaring that the system dissipated early on September 6, the JTWC began monitoring the re-developing system later that day. Convective banding had reformed, wind shear had decreased and the cyclone had less interaction with land as it slowly moved further into the South China Sea. However, late on September 8, both agencies declared that the depression had dissipated off the coast of Vietnam.

Impact

At least six people were killed, three were left missing and nine were injured by the depression throughout Vietnam. Rainfall from the storm exceeded 430 mm, triggering widespread flash flooding. A maximum of 540 mm fell in Huế.{{cite web|author=Government of Vietnam|publisher=ReliefWeb|date=September 7, 2009|access-date=September 8, 2009|title=Tropical low swamps 900 houses

Numerous bridges were washed away by flood waters exceeding 1.5 m, isolating several communities. In the Sơn Tịnh District, 76 structures were destroyed by flooding and high winds. More than 200 homes were inundated by up to 0.7 m of flood waters in the communities of Hoa Tho Dong and Hoa Phat. At least one ship sank and officials lost contact with two others; officials stated that 1,178 boats were in the South China Sea in the storm. In the valleys of Tam Kỳ and Phú Ninh, nearly 1,000 homes were inundated by water. Roughly 20% of the 373,000 students starting school were told to remain home as their schools were closed due to flood waters. By September 7, officials in Quảng Nam Province estimated that property damages from the depression had reached 20 billion (VND; $1.12 million USD) and agricultural losses amounted to 25 billion (VND; $1.4 million USD). Throughout other regions, at least 100 structures were damaged and more than 20,000 hectares of crops were submerged in flood waters. Damages to irrigation systems throughout the county amounted to 3 billion (VND; $168,000 USD). Total damages from the system in Vietnam were estimated at 542 billion (VND; $32 million USD) and 13 people were dead.

References

References

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6. (September 5, 2009). "Significant Tropical Weather Outlook for the Western and South Pacific Oceans".
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