September 2009 Vietnam tropical depression
Encyclopedia
The September 2009 Vietnam tropical depression was a weak tropical depression that produced 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
banding features
began to develop and shower and thunderstorm activity formed near the center. On September 4, the Joint Typhoon Warning Center
issued a Tropical Cyclone Formation Alert
; however, a sudden increase in wind shear
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
(JMA) continued to issue advisories until the depression dissipated during September 9.
Although the depression did not make landfall, the outer effects of the storm led to heavy rainfall throughout central Vietnam, peaking at 430 mm (16.9 in). The ensuing flood 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 Quang Nam Province
, damages from the system were estimated at 45 billion (VND; $2.52 million USD
).
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 temperature
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.
. Sixty-one tons of fish were swept away during the floods and 8,700 hectares of rice were destroyed. The city of Da Nang
sustained the worst flooding from the storm, with some areas reporting flood depths of 0.8 m (2.6 ft). 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
, 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 1.5 m (4.9 ft), 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 (2.3 ft) 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 Quang 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).
Atmospheric convection
Atmospheric convection is the result of a parcel-environment instability, or temperature difference, layer in the atmosphere. Different lapse rates within dry and moist air lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to...
banding features
Rainband
A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as...
began to develop and shower and thunderstorm activity formed near the center. On September 4, the Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...
issued a Tropical Cyclone Formation Alert
Tropical Cyclone Formation Alert
A Tropical Cyclone Formation Alert is a bulletin released by the U.S. Navy-operated Joint Typhoon Warning Center in Honolulu, Hawaii or the Naval Maritime Forecast Center in Norfolk, Virginia, warning of the possibility of a tropical cyclone forming from a tropical disturbance that has been...
; however, a sudden increase in wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
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
Japan Meteorological Agency
The or JMA, is the Japanese government's weather service. Charged with gathering and reporting weather data and forecasts in Japan, it is a semi-autonomous part of the Ministry of Land, Infrastructure and Transport...
(JMA) continued to issue advisories until the depression dissipated during September 9.
Although the depression did not make landfall, the outer effects of the storm led to heavy rainfall throughout central Vietnam, peaking at 430 mm (16.9 in). The ensuing flood 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 Quang Nam Province
Quang Nam Province
Quảng Nam is a province on the South Central Coast of Vietnam. It is bordered by Thua Thien-Huế province to the north, the nation of Laos to the west, Kon Tum Province to the southwest, Quảng Ngãi Province to the southeast, the South China Sea to the east, and the city of Da Nang to the...
, damages from the system were estimated at 45 billion (VND; $2.52 million USD
United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....
).
Meteorological history
The tropical depression originated from an area of low pressureLow pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
in the South China Sea
South China Sea
The South China Sea is a marginal sea that is part of the Pacific Ocean, encompassing an area from the Singapore and Malacca Straits to the Strait of Taiwan of around...
on September 1. Scattered convection
Atmospheric convection
Atmospheric convection is the result of a parcel-environment instability, or temperature difference, layer in the atmosphere. Different lapse rates within dry and moist air lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to...
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
Outflow (meteorology)
Outflow, in meteorology, is air that flows outwards from a storm system. It is associated with ridging, or anticyclonic flow. In the low levels of the troposphere, outflow radiates from thunderstorms in the form of a wedge of rain-cooled air, which is visible as a thin rope-like cloud on weather...
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
Eye (cyclone)
The eye is a region of mostly calm weather found at the center of strong tropical cyclones. The eye of a storm is a roughly circular area and typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the second most severe weather of a cyclone...
and weak diffluence was noted around the system due to an anticyclone
Anticyclone
An anticyclone is a weather phenomenon defined by the United States' National Weather Service's glossary as "[a] large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere"...
to the north. With low wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
, convective banding features
Rainband
A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as...
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
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...
(JTWC) issued a Tropical Cyclone Formation Alert
Tropical Cyclone Formation Alert
A Tropical Cyclone Formation Alert is a bulletin released by the U.S. Navy-operated Joint Typhoon Warning Center in Honolulu, Hawaii or the Naval Maritime Forecast Center in Norfolk, Virginia, warning of the possibility of a tropical cyclone forming from a tropical disturbance that has been...
(TCFA) as the depression was likely to intensify as it was situated over high sea surface temperature
Sea surface temperature
Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...
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 430 mm (16.9 in), triggering widespread flash flooding. A maximum of 540 mm (21.3 in) fell in HuếHue
Hue is one of the main properties of a color, defined technically , as "the degree to which a stimulus can be describedas similar to or different from stimuli that are described as red, green, blue, and yellow,"...
. Sixty-one tons of fish were swept away during the floods and 8,700 hectares of rice were destroyed. The city of Da Nang
Da Nang
Đà Nẵng , occasionally Danang, is a major port city in the South Central Coast of Vietnam, on the coast of the South China Sea at the mouth of the Han River. It is the commercial and educational center of Central Vietnam; its well-sheltered, easily accessible port and its location on the path of...
sustained the worst flooding from the storm, with some areas reporting flood depths of 0.8 m (2.6 ft). 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
Quang Ngai Province
Quảng Ngãi is a province in the South Central Coast region of Vietnam, on the coast of South China Sea. It is located 883 km south of Hanoi and 838 km north of Ho Chi Minh City.-History:...
, 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
Quang Tri Province
Quảng Trị is a province on the North Central Coast of Vietnam, north of the former imperial capital of Huế.-Geography:Located in North Central Vietnam, Quang Tri Province is surrounded by Quang Binh Province on the north, Thua Thien-Hue Province on the south, Savannakhet Province of Laos on the...
were advised to evacuate to safer areas as numerous landslides threatened homes.
Numerous bridges were washed away by flood waters exceeding 1.5 m (4.9 ft), 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 (2.3 ft) 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 Quang Nam Province
Quang Nam Province
Quảng Nam is a province on the South Central Coast of Vietnam. It is bordered by Thua Thien-Huế province to the north, the nation of Laos to the west, Kon Tum Province to the southwest, Quảng Ngãi Province to the southeast, the South China Sea to the east, and the city of Da Nang to the...
estimated that property damages from the depression had reached 20 billion (VND; $1.12 million USD
United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....
) 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).
See also
- 2009 Pacific typhoon season2009 Pacific typhoon seasonThe 2009 Pacific typhoon season was the period that tropical cyclones formed in the Western Pacific Ocean. The season ran throughout the year during 2009, with most tropical cyclones forming between May and November. The scope of this article is limited to the Pacific Ocean, north of the equator...
- Timeline of the 2009 Pacific typhoon seasonTimeline of the 2009 Pacific typhoon seasonThis timeline documents all of the events of the 2009 Pacific typhoon season which was the period that tropical cyclones formed in the Western Pacific Ocean during 2009, with most of the tropical cyclones forming between May and November. The scope of this article is limited to the Pacific Ocean,...