The September 2009 Vietnam tropical depression was a weak tropical depression that caused deadly flooding throughout central Vietnam in early September. Forming out of an area of low pressure on September 3, the depression hardly intensified as it meandered off the coast of Vietnam. Initially situated in a favorable environment,

convective Convection is single or multiphase fluid flow that occurs spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

banding features began to develop and shower and thunderstorm activity formed near the center. On September 4, the

Joint Typhoon Warning Center The Joint Typhoon Warning Center (JTWC) is a joint United States Navy – United States Air Force command in Pearl Harbor, Hawaii. The JTWC is responsible for the issuing of tropical cyclone warnings in the North-West Pacific Ocean, South P ...

issued a

Tropical Cyclone Formation Alert A Tropical Cyclone Formation Alert (TCFA) is a bulletin released by the U.S. Navy-operated Joint Typhoon Warning Center in Honolulu, Hawaii or the Fleet Weather Center in Norfolk, Virginia, warning of the possibility of a tropical cyclone formi ...

; however, a sudden increase in

wind shear Wind shear (; also written windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical ...

caused the system to rapidly become disorganized, leading to the cancellation of the alert the next day. The system continued to slowly track off the coast of Vietnam, nearly dissipating on September 5, before becoming better organized. However, the depression remained weak, with the JTWC reporting on September 7 that the depression had dissipated, though the

Japan Meteorological Agency The Japan Meteorological Agency (JMA; ''気象庁, Kishō-chō'') is a division of the Ministry of Land, Infrastructure, Transport and Tourism dedicated to the Scientific, scientific observation and research of natural phenomena. Headquartered ...

(JMA) continued to issue advisories until the depression dissipated during September 9. Although the depression did not make landfall, the outer rainbands of the storm led to heavy rainfall throughout central Vietnam, peaking at . The ensuing floods killed at least six people and left three others missing. Large areas of cropland were inundated by the waters and numerous homes were damaged. In Quảng Nam Province, damages from the system were estimated at 45 billion ( VND; $2.52 million

USD The United States dollar (symbol: $; currency code: USD) is the official currency of the United States and several other countries. The Coinage Act of 1792 introduced the U.S. dollar at par with the Spanish silver dollar, divided it int ...

Meteorological history

The tropical depression originated from an

area of low pressure In meteorology, a low-pressure area (LPA), low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. It is the opposite of a high-pressure area. Low-pressure areas are commonly associated with inclem ...

in the

South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by South China, in the west by the Indochinese Peninsula, in the east by the islands of Taiwan island, Taiwan and northwestern Philippines (mainly Luz ...

on September 1. Scattered

convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

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 A high-pressure area, high, or anticyclone, is an area near the surface of a planet where the atmospheric pressure is greater than the pressure in the surrounding regions. Highs are middle-scale meteorological features that result from interpl ...

to the north. With low

, 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

(JTWC) issued a

(TCFA) as the depression was likely to intensify as it was situated over high

sea surface temperature Sea surface temperature (or ocean surface temperature) is the ocean temperature, temperature of ocean water close to the surface. The exact meaning of ''surface'' varies in the literature and in practice. It is usually between and below the sea ...

s 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 , triggering widespread flash flooding. A maximum of fell in

Huế Huế (formerly Thừa Thiên Huế province) is the southernmost coastal Municipalities of Vietnam, city in the North Central Coast region, the Central Vietnam, Central of Vietnam, approximately in the center of the country. It borders Quảng ...

. Sixty-one tons of fish were swept away during the floods and 8,700 hectares of rice fields were destroyed. The city of

Da Nang Da Nang or DanangSee also Danang Dragons (, ) is the fifth-largest city in Vietnam by municipal population. It lies on the coast of the Western Pacific Ocean of Vietnam at the mouth of the Hàn River, and is one of Vietnam's most important p ...

sustained the worst flooding from the storm, with some areas reporting flood depths of . Schools throughout the area were closed as many residents were unable to pass through flooded streets. A sixth grader drowned in the city after the boat he was on overturned in flood waters. In Huế, a two-year-old drowned in flood waters on September 4. A large section of highway 14B, connecting Nam Đông and Huế was washed away. In

Quảng Ngãi Province Quảng Ngãi is a northern coastal Provinces of Vietnam, province in the South Central Coast region, the Central Vietnam, Central of Vietnam. It borders Quảng Nam to the north, Bình Định to the south, Kon Tum province, Kon Tum to the ...

, two fishermen were left missing and five other people were injured by the storm. At least three homes sustained severe damage. Residents throughout Quảng Trị Province were advised to evacuate to safer areas as numerous landslides threatened homes. Numerous bridges were washed away by flood waters exceeding , isolating several communities. In the

Sơn Tịnh District ''Toxicodendron succedaneum'', the wax tree, Japanese Hazenoki tree (Sumac or wax tree), sơn in Vietnamese or charão in Portuguese, is a flowering plant species in the genus '' Toxicodendron'' found in Asia, although it has been planted else ...

, 76 structures were destroyed by flooding and high winds. More than 200 homes were inundated by up to 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

) 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).

References

External links

Japan Meteorological AgencyJoint Typhoon Warning Center

Vietnam's National Hydro-Meteorological Service
{{DEFAULTSORT:2009 09 Vietnam tropical depression 2009 Vietnam 2009 Vietnam Typhoons in Vietnam 2009 in Vietnam 2009 September Vietnam tropical depression 2009 disasters in Vietnam