.gif)
Typhoon Sepat (2007)
Encyclopedia
Typhoon Sepat was the eighth tropical storm of the 2007 Pacific typhoon season
that affected the Philippines
and made landfall in Taiwan
and Fujian
.
about 1280 km (795.4 mi) southeast of Naha, Okinawa
. Northerly upper-level winds initially provided beneficial divergence
, though also resulted in detrimental wind shear
and lack of inflow
. Upper-level conditions gradually became more favorable for development as the disturbance tracked along the eastern periphery of an upper-level anticyclone
. With convective rain bands wrapping into the circulation, the Joint Typhoon Warning Center
(JTWC) issued a tropical cyclone formation alert
on the system late on August 11. Remaining nearly stationary between ridges
to its northeast and southwest, the system developed further, and early on August 12 the JTWC classified it as Tropical Depression 09W. Shortly thereafter, the Japan Meteorological Agency
(JMA) classified it as a tropical depression while located about 1245 km (773.6 mi) southeast of Okinawa.
Twelve hours later, the JTWC upgraded the tropical depression to a tropical storm based on Dvorak technique
satellite intensity estimates and the storm exhibiting tightly-curved convective
bands. An upper-level low helped to reduce wind shear
that had been affecting the storm. The JTWC also warned of the possibility of rapid intensification. The JMA upgraded the depression to a tropical storm later that day and named it Sepat
, a name contributed by Malaysia referring to a freshwater fish species.
By early the next morning, August 13, Sepat had a banding eye
visible on microwave satellite imagery and had remained in an environment conducive for strengthening, including weakening wind shear. An upper-level anticyclone
also moved over the storm. By now, Sepat had moved into PAGASA
's area of responsibility and attained the local name "Egay". The JMA upgraded Sepat to a severe tropical storm shortly after. Sepat continued to slowly gain more organisation and intensify further, and started to move faster under the influence of a subtropical steering ridge. Sepat strengthened into a typhoon on the morning of August 14 under still-decreasing wind shear and favourable diffluence.
Sepat developed a cloud-filled eye measuring 12 nmi (22.2 km; 13.8 mi) across by later that night, part of a larger central dense overcast nearly 130 nmi (240.8 km), 150 mi) wide. Favourable sea surface temperature
s of 29 – allowed Sepat to continue intensifying despite decrease of poleward
outflow
. By this time, Sepat had deepened to 955 hPa
. The JTWC also noted possible imminent rapid intensification of the storm.
Late that night, Sepat underwent rapid intensification as expected, and was upgraded by the JTWC to a super typhoon the next morning. The JMA analysed Sepat at 940 hPa
at the same time. The deep convection warmed slightly and underwent slight fluctuations during the afternoon. During this period, Sepat slowed in forward speed and took a turn from a west-southwest motion to a more poleward one. Its eye also cleared out, became slightly larger, and warmed. By late that night, Sepat had become the strongest storm of the season to date, with the JMA analysing its pressure at 925 hPa
, lower than Typhoon Man-yi's minimum of 935 hPa
.
Continuing to intensify, Sepat reached a peak minimum central pressure of 910 hPa
on the morning of August 16. It also managed to maintain its cloud-free eye. High ocean heat content and good equator
ward outflow
allowed Sepat to maintain its intensity, but an eyewall replacement cycle
began later that night. The eyewall replacement cycle continued throughout the night, and by the next morning Sepat displayed concentric eyewalls, with the inner eyewall being weaker. The JTWC downgraded it to a typhoon later that evening.
It made landfall
in eastern Taiwan
between Taitung
and Hualien on the morning of August 18 local time at around 5 a.m. (2100 UTC August 17) and weakened to a minimal typhoon. After crossing the island, Sepat held on to minimal typhoon intensity before weakening to a severe tropical storm that night. It made a second landfall, in China, about 24 hours after landfall on Taiwan and was downgraded to a tropical storm the next morning. It further weakened inland and the JMA issued its final advisory on the morning of August 20.
issued sea typhoon warnings on the morning of August 16 and land warnings later that evening. At all county and city levels, a typhoon holiday was declared for August 18 in preparation for the storm. In the Philippines
, PAGASA
issued Public Storm Warning Signals 1 to 3 (4 is the highest signal) for most provinces of Luzon
.
Over 900,000 people were evacuated in eastern China
, and over 100 flights had to be cancelled. In Taiwan, nearly 2,000 people had to be evacuated.
After Sepat made landfall in China, the regional meteorological office in Hunan Province sent over 2.25 million text messages to residents to warn them about the storm's remnants.
. Classes and services in government offices were suspended until August 17. At least three people drowned. About 200 people were evacuated from Manila due to flooding.
Heavy rainfall in Taiwan, which reached 984 mm (38.7 in) at Tianhsiang in Hualien, resulted in numerous mudslides, especially in mountain regions and in the south while the combination of the precipitation and winds caused an estimated $1.14 billion (2007 NT$
, $34.5 million 2007 USD
) in agricultural damage. More than 70,000 homes lost power, and nearly a week after the storm passed through 9,000 people remained without electricity.
The Suao-Hualien Highway was also closed due to landslides brought by the typhoon. One person was reported killed in Taiwan.
, killing 13 people and injuring at least 60 more. Most counties received almost 200 mm (7.9 in) of rainfall. Sepat caused landslides in Fujian
, leaving 12 people missing. Landslides were the cause of at least half the 39 deaths in China. Damage was also reported in Jiangxi
and Hunan
, and damage in the four provinces was estimated at 5 billion yuan (US$658 million).
2007 Pacific typhoon season
The 2007 Pacific typhoon season was a below average season which featured 24 named storms and 14 typhoons, compared to the average of 27 and 17 respectively. had no official bounds; it ran year-round in 2007, but most tropical cyclones tend to form in the northwestern Pacific Ocean between May and...
that affected the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
and made landfall in Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
and Fujian
Fujian
' , formerly romanised as Fukien or Huguing or Foukien, is a province on the southeast coast of mainland China. Fujian is bordered by Zhejiang to the north, Jiangxi to the west, and Guangdong to the south. Taiwan lies to the east, across the Taiwan Strait...
.
Meteorological history
On August 11, a low-level circulation center formed in conjunction with a persistent area of convectionAtmospheric 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...
about 1280 km (795.4 mi) southeast of Naha, Okinawa
Naha, Okinawa
is the capital city of the Japanese prefecture of Okinawa.Naha is a coastal city located on the East China Sea coast of the southern part of Okinawa Island, the largest of the Ryukyu Islands...
. Northerly upper-level winds initially provided beneficial divergence
Divergence
In vector calculus, divergence is a vector operator that measures the magnitude of a vector field's source or sink at a given point, in terms of a signed scalar. More technically, the divergence represents the volume density of the outward flux of a vector field from an infinitesimal volume around...
, though also resulted in detrimental 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...
and lack of inflow
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...
. Upper-level conditions gradually became more favorable for development as the disturbance tracked along the eastern periphery of an upper-level 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"...
. With convective rain bands wrapping into the circulation, 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...
on the system late on August 11. Remaining nearly stationary between ridges
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
to its northeast and southwest, the system developed further, and early on August 12 the JTWC classified it as Tropical Depression 09W. Shortly thereafter, 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) classified it as a tropical depression while located about 1245 km (773.6 mi) southeast of Okinawa.
Twelve hours later, the JTWC upgraded the tropical depression to a tropical storm based on Dvorak technique
Dvorak technique
The Dvorak technique is a widely used system to subjectively estimate tropical cyclone intensity based solely on visible and infrared satellite images. Several agencies issue Dvorak intensity numbers for cyclones of sufficient intensity...
satellite intensity estimates and the storm exhibiting tightly-curved convective
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...
bands. An upper-level low helped to reduce 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...
that had been affecting the storm. The JTWC also warned of the possibility of rapid intensification. The JMA upgraded the depression to a tropical storm later that day and named it Sepat
Sepat
Sepat may refer to:* sepat, the Ancient Egyptian name for the regional divisions of the country. The Greek term nome has been used since the Ptolemaic period. Nome_...
, a name contributed by Malaysia referring to a freshwater fish species.
By early the next morning, August 13, Sepat had a banding eye
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...
visible on microwave satellite imagery and had remained in an environment conducive for strengthening, including weakening wind shear. An upper-level 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"...
also moved over the storm. By now, Sepat had moved into PAGASA
Philippine Atmospheric, Geophysical and Astronomical Services Administration
The Philippine Atmospheric, Geophysical and Astronomical Services Administration is a Philippine national institution dedicated to provide flood and typhoon warnings, public weather forecasts and advisories, meteorological, astronomical, climatological, and other specialized information and...
's area of responsibility and attained the local name "Egay". The JMA upgraded Sepat to a severe tropical storm shortly after. Sepat continued to slowly gain more organisation and intensify further, and started to move faster under the influence of a subtropical steering ridge. Sepat strengthened into a typhoon on the morning of August 14 under still-decreasing wind shear and favourable diffluence.
Sepat developed a cloud-filled eye measuring 12 nmi (22.2 km; 13.8 mi) across by later that night, part of a larger central dense overcast nearly 130 nmi (240.8 km), 150 mi) wide. Favourable 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 of 29 – allowed Sepat to continue intensifying despite decrease of poleward
Geographical pole
A geographical pole is either of the two points—the north pole and the south pole—on the surface of a rotating planet where the axis of rotation meets the surface of the body...
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...
. By this time, Sepat had deepened to 955 hPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
. The JTWC also noted possible imminent rapid intensification of the storm.
Late that night, Sepat underwent rapid intensification as expected, and was upgraded by the JTWC to a super typhoon the next morning. The JMA analysed Sepat at 940 hPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
at the same time. The deep convection warmed slightly and underwent slight fluctuations during the afternoon. During this period, Sepat slowed in forward speed and took a turn from a west-southwest motion to a more poleward one. Its eye also cleared out, became slightly larger, and warmed. By late that night, Sepat had become the strongest storm of the season to date, with the JMA analysing its pressure at 925 hPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
, lower than Typhoon Man-yi's minimum of 935 hPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
.
Continuing to intensify, Sepat reached a peak minimum central pressure of 910 hPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
on the morning of August 16. It also managed to maintain its cloud-free eye. High ocean heat content and good equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
ward 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...
allowed Sepat to maintain its intensity, but an eyewall replacement cycle
Eyewall replacement cycle
Eyewall replacement cycles, also called concentric eyewall cycles, naturally occur in intense tropical cyclones, generally with winds greater than 185 km/h , or major hurricanes...
began later that night. The eyewall replacement cycle continued throughout the night, and by the next morning Sepat displayed concentric eyewalls, with the inner eyewall being weaker. The JTWC downgraded it to a typhoon later that evening.
It made landfall
Landfall (meteorology)
Landfall is the event of a tropical cyclone or a waterspout coming onto land after being over water. When a waterspout makes landfall it is reclassified as a tornado, which can then cause damage inland...
in eastern Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
between Taitung
Taitung City
Taitung City is the county seat of Taitung County, Taiwan. It lies on the southeast coast of Taiwan facing the Pacific Ocean.The city is served by Taitung Airport. Taitung is a gateway to Green Island and Orchid Island, both of which are very popular among Taiwanese tourists.-History:Taitung...
and Hualien on the morning of August 18 local time at around 5 a.m. (2100 UTC August 17) and weakened to a minimal typhoon. After crossing the island, Sepat held on to minimal typhoon intensity before weakening to a severe tropical storm that night. It made a second landfall, in China, about 24 hours after landfall on Taiwan and was downgraded to a tropical storm the next morning. It further weakened inland and the JMA issued its final advisory on the morning of August 20.
Preparations
The Government of the Republic of ChinaGovernment of the Republic of China
The Republic of China was formally established by Dr. Sun Yat-sen in 1912 in Nanjing under the Provisional Constitution of the Republic of China but this government was moved to Beijing in the same year and continued as the internationally recognized government of China until 1928. In the history...
issued sea typhoon warnings on the morning of August 16 and land warnings later that evening. At all county and city levels, a typhoon holiday was declared for August 18 in preparation for the storm. In the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, PAGASA
Philippine Atmospheric, Geophysical and Astronomical Services Administration
The Philippine Atmospheric, Geophysical and Astronomical Services Administration is a Philippine national institution dedicated to provide flood and typhoon warnings, public weather forecasts and advisories, meteorological, astronomical, climatological, and other specialized information and...
issued Public Storm Warning Signals 1 to 3 (4 is the highest signal) for most provinces of Luzon
Luzon
Luzon is the largest island in the Philippines. It is located in the northernmost region of the archipelago, and is also the name for one of the three primary island groups in the country centered on the Island of Luzon...
.
Over 900,000 people were evacuated in eastern China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, and over 100 flights had to be cancelled. In Taiwan, nearly 2,000 people had to be evacuated.
After Sepat made landfall in China, the regional meteorological office in Hunan Province sent over 2.25 million text messages to residents to warn them about the storm's remnants.
Philippines
On August 15, monsoon rains brought by Typhoon Sepat flooded and paralyzed traffic in Metro ManilaMetro Manila
Metropolitan Manila , the National Capital Region , or simply Metro Manila, is the metropolitan region encompassing the City of Manila and its surrounding areas in the Philippines...
. Classes and services in government offices were suspended until August 17. At least three people drowned. About 200 people were evacuated from Manila due to flooding.
Taiwan
Sustained winds of 126 km/h (78.3 mph) were recorded off the Taiwanese coast on August 18 as Sepat moved through the country.Heavy rainfall in Taiwan, which reached 984 mm (38.7 in) at Tianhsiang in Hualien, resulted in numerous mudslides, especially in mountain regions and in the south while the combination of the precipitation and winds caused an estimated $1.14 billion (2007 NT$
New Taiwan dollar
The New Taiwan dollar , or simply Taiwan dollar, is the official currency of the Taiwan Area of the Republic of China since 1949, when it replaced the Old Taiwan dollar...
, $34.5 million 2007 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....
) in agricultural damage. More than 70,000 homes lost power, and nearly a week after the storm passed through 9,000 people remained without electricity.
The Suao-Hualien Highway was also closed due to landslides brought by the typhoon. One person was reported killed in Taiwan.
Mainland China
In Fujian Province, Sepat's winds felled billboards and ripped roofs off houses and two people were killed, while a tornado was reported in ZhejiangZhejiang
Zhejiang is an eastern coastal province of the People's Republic of China. The word Zhejiang was the old name of the Qiantang River, which passes through Hangzhou, the provincial capital...
, killing 13 people and injuring at least 60 more. Most counties received almost 200 mm (7.9 in) of rainfall. Sepat caused landslides in Fujian
Fujian
' , formerly romanised as Fukien or Huguing or Foukien, is a province on the southeast coast of mainland China. Fujian is bordered by Zhejiang to the north, Jiangxi to the west, and Guangdong to the south. Taiwan lies to the east, across the Taiwan Strait...
, leaving 12 people missing. Landslides were the cause of at least half the 39 deaths in China. Damage was also reported in Jiangxi
Jiangxi
' is a southern province in the People's Republic of China. Spanning from the banks of the Yangtze River in the north into hillier areas in the south, it shares a border with Anhui to the north, Zhejiang to the northeast, Fujian to the east, Guangdong to the south, Hunan to the west, and Hubei to...
and Hunan
Hunan
' is a province of South-Central China, located to the south of the middle reaches of the Yangtze River and south of Lake Dongting...
, and damage in the four provinces was estimated at 5 billion yuan (US$658 million).
See also
- List of notable tropical cyclones
- 2007 Pacific typhoon season2007 Pacific typhoon seasonThe 2007 Pacific typhoon season was a below average season which featured 24 named storms and 14 typhoons, compared to the average of 27 and 17 respectively. had no official bounds; it ran year-round in 2007, but most tropical cyclones tend to form in the northwestern Pacific Ocean between May and...
- Timeline of the 2007 Pacific typhoon seasonTimeline of the 2007 Pacific typhoon seasonThe 2007 Pacific typhoon season had no official bounds; it ran year-round in 2007, but most tropical cyclones tend to form in the northwestern Pacific Ocean between May and November...