Tropical Storm Etau (2009)

Tropical Storm Etau was the deadliest tropical cyclone to impact Japan since Typhoon Tokage in 2004. Forming on August 8, 2009 from an area of low pressure, the system gradually intensified into a tropical storm. Tracking in a curved path around the edge of a subtropical ridge, Etau continued to intensify as it neared Japan. By August 10, the cyclone reached its peak intensity as a weak tropical storm with winds of 75 km/h (45 mph 10-minute sustained) and a barometric pressure of 992 hPa (mbar). Shortly after, Etau began to weaken. Increasing wind shear led to the center becoming devoid of convection and the system eventually weakened to a tropical depression on August 13. The remnants of Etau persisted for nearly three days before dissipating early on August 16.

Tropical Storm Etau
Tropical Storm Etau at peak intensity on August 10
Meteorological history
FormedAugust 8, 2009
ExtratropicalAugust 14, 2009
DissipatedAugust 16, 2009
Tropical storm
10-minute sustained (JMA)
Highest winds75 km/h (45 mph)
Lowest pressure992 hPa (mbar); 29.29 inHg
Tropical storm
1-minute sustained (SSHWS/JTWC)
Highest winds75 km/h (45 mph)
Lowest pressure992 hPa (mbar); 29.29 inHg
Overall effects
Fatalities28 total
Damage$87.5 million (2009 USD)
Areas affectedJapan (particularly Hyōgo Prefecture)
IBTrACS
Part of the 2009 Pacific typhoon season

Although Etau did not make landfall, the outer bands of the storm produced torrential rainfall in Japan, peaking at 326.5 mm (12.85 in). These rains triggered deadly flooding and mudslides, especially in Hyōgo Prefecture. Twenty-eight people were killed by the storm and ¥7.1 billion (US$87.5 million) in damage occurred throughout the affected region.[1][2] According to the Fire and Disaster Management Agency, a total of 5,602 homes were flooded and 183 were destroyed. Following the storm, 600 Japanese soldiers were deployed from Tokyo to assist in cleanup efforts.

Meteorological history
Map plotting the storm's track and intensity, according to the Saffir–Simpson scale
Map key
Saffir–Simpson scale
  Tropical depression (≤38 mph, ≤62 km/h)
  Tropical storm (39–73 mph, 63–118 km/h)
  Category 1 (74–95 mph, 119–153 km/h)
  Category 2 (96–110 mph, 154–177 km/h)
  Category 3 (111–129 mph, 178–208 km/h)
  Category 4 (130–156 mph, 209–251 km/h)
  Category 5 (≥157 mph, ≥252 km/h)
  Unknown
Storm type
triangle Extratropical cyclone, remnant low, tropical disturbance, or monsoon depression

Tropical Storm Etau originated on August 5 out of an area of low pressure associated with disorganized convective activity located about 550 km (280 mi) east-northeast of Guam.[3] The following day, the system relocated several dozen kilometers to the north. Convective turning began to appear on satellite imagery and a tropical upper tropospheric trough (TUTT) cell to the north provided a northward component to the system's movement.[4] Early on August 7, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert for the developing system as deep convection consolidated around the low-pressure system.[5] Around 0000 UTC on August 8, the Japan Meteorological Agency (JMA) designated the system as a tropical depression.[6]

Several hours later on August 8, the JTWC also declared the system a tropical depression, classifying it at 10W.[7] Later that day, convection associated with the depression became disorganized, preventing intensification of the system. The depression generally tracked towards the northwest during the day in response a subtropical ridge to the north.[8] By August 9, the center of circulation became more defined as convection wrapped around it.[9] Around 1200 UTC, the JMA upgraded the depression to a tropical storm and gave it the name Etau.[10] The JTWC, however, did not upgrade the system to a tropical storm for several more hours.[11] On August 10, the JTWC briefly downgraded the storm to a tropical depression.[12] By this time, the system had re-curved to the east around the western periphery of the subtropical ridge. Etau also became slightly disorganized as it began to interact with the baroclinic zone near Japan.[13] Early on August 11, the JMA reported that the storm winds had peaked at 75 km/h (45 mph 10-minute sustained) and a barometric pressure of 992 hPa (mbar).[14] Later that day, the storm once more became slightly disorganized due to increased wind shear; however, the JTWC reported that the storm intensified based on satellite intensity estimates and weather radar imagery from Japan.[15]

Later on August 11, the center of Etau became partially devoid of convection, with only a narrow band of shower and thunderstorm activity persisting to the southeast of the center.[16] Increasing wind shear prevented convection from redeveloping and the storm continued to weaken.[17] Early the following day, the JTWC issued their final advisory on Etau as they reported it had weakened to a tropical depression well to the east of Japan.[18] Roughly 24 hours later, the JMA also downgraded the system to a tropical depression.[19] The final advisory on Etau was issued by the JMA early on August 14 as it slowly tracked northward.[20]

Preparations, impact and aftermath
Debris filled street in Sayo after flood waters receded

In anticipation of wind gusts up to 126 km/h (78 mph) and heavy rains, Japanese officials evacuated roughly 47,000 residents from western regions along the coast as gale warnings were declared by the JMA. Officials also feared that flooding from Tropical Storm Etau would mirror that of Typhoon Morakot in Taiwan where at least 14 were killed in the country's worst flood in 50 years.[21][22] Six flights in the country were canceled after a plane was struck by lightning. Fifteen railway services were also canceled due to heavy rains.[23] According to officials in Japan, nearly 140,000 people were evacuated to shelters in relation to flooding and landslides produced by Etau.[1]

As Tropical Storm Etau brushed Japan on August 10, torrential rains fell within its outer bands. In a 24‑hour span, a record 326.5 mm (12.85 in) of rain fell, triggering extensive flooding and landslides.[24] Initial reports stated that 13 people were killed and 10 others were missing due to the storm.[25] Most of the fatalities took place in Hyōgo Prefecture where hundreds of homes were flooded and numerous others were damaged or destroyed by landslides.[26] In some areas, flood waters reached a depth of 1.5 m (4.9 ft).[24] One man drowned after driving his car into a flooded street and being overcome by the water.[27] Another person was killed after her home was destroyed by a landslide in Okayama prefecture.[28]

In Tokushima, two people were listed as missing and two others sustained serious injuries.[23] Later news reports stated that up to 18 people were missing following further landslides. The affected region was especially susceptible to landslides due to recent seismic activity, with a magnitude 6.4 earthquake taking place on August 10.[29] By August 11, one of the missing persons was confirmed to have been killed during the storm. About 800 people were placed in public shelters and 53,000 homes were left without running water. By August 12, a total of 18 people were confirmed to have been killed and nine others were still missing.[30] Three bridges in Tokushima were also washed away.[31] Days later, the Japanese Fire and Disaster Management Agency finalized the death toll at 26 with one other missing,[1][2] making Etau the deadliest tropical cyclone to impact Hyōgo Prefecture, Japan since Typhoon Tokage in 2004.[32] Throughout several prefectures, 5,602 homes were flooded and 183 were destroyed. Landslides triggered by the storm damaged another 2,109 structures, most of which were in Okayama and Hyōgo prefectures.[1] Following severe damages, in the town of Sayo it requested assistance from the national government. As a result, more than 200 troops were deployed to the town.[23][24] A post-disaster office was also set up by the prime minister's office crisis management center.[24] An additional 400 troops were deployed to the city by August 11 to assist in rescue efforts.[31]

See also

References
  1. 平成21年台風第9号による被害状況等について(第19報) [Casualties, Damage and so on by Typhoon No.9 in 2009 (Revision 19)] (PDF) (in Japanese). Fire and Disaster Management Agency. March 15, 2010. Archived from the original (PDF) on July 21, 2011. Retrieved August 29, 2009.
  2. 県西・北部豪雨 行方不明の男児、法律上「死亡」 [A boy, who has been missing by torrents, "died" in law]. Kobe Shimbun (in Japanese). March 9, 2011. Retrieved March 9, 2011.
  3. "Significant Tropical Weather Advisory for the western and southern Pacific oceans". Joint Typhoon Warning Center. August 5, 2009. Retrieved August 14, 2009.
  4. "Significant Tropical Weather Advisory for the western and southern Pacific oceans". Joint Typhoon Warning Center. August 6, 2009. Retrieved August 14, 2009.
  5. "Tropical Cyclone Formation Alert". Joint Typhoon Warning Center. August 7, 2009. Retrieved August 14, 2009.
  6. "WWJP25 2009-08-08, 0000z". Japan Meteorological Agency. August 8, 2009. Retrieved August 14, 2009.
  7. "Tropical Depression 10W Advisory One". Joint Typhoon Warning Center. August 8, 2009. Retrieved August 14, 2009.
  8. "Tropical Depression 10W Prognostic Reasoning Three". Joint Typhoon Warning Center. August 8, 2009. Retrieved August 14, 2009.
  9. "Tropical Depression 10W Prognostic Reasoning Five". Joint Typhoon Warning Center. August 9, 2009. Retrieved August 14, 2009.
  10. "WTPQ21 RJTD 091200". Japan Meteorological Agency. August 9, 2009. Archived from the original on August 9, 2009. Retrieved August 14, 2009.
  11. "Tropical Storm 10W (Etau) Advisory Eight". Joint Typhoon Warning Center. August 9, 2009. Retrieved August 14, 2009.
  12. "Tropical Depression 10W (Etau) Advisory Eleven". Joint Typhoon Warning Center. August 10, 2009. Retrieved August 14, 2009.
  13. "Tropical Depression 10W (Etau) Prognostic Reasoning Eleven". Joint Typhoon Warning Center. August 10, 2009. Retrieved August 14, 2009.
  14. "RSMC Tropical Cyclone Best Track". Japan Meteorological Agency. October 2, 2009. Archived from the original on May 27, 2012. Retrieved 2009-11-18.
  15. "Tropical Storm 10W (Etau) Prognostic Reasoning Thirteen". Joint Typhoon Warning Center. August 11, 2009. Retrieved August 14, 2009.
  16. "Tropical Storm 10W (Etau) Advisory Fourteen". Joint Typhoon Warning Center. August 11, 2009. Retrieved August 29, 2009.
  17. "Tropical Storm 10W (Etau) Advisory Sixteen". Joint Typhoon Warning Center. August 11, 2009. Retrieved August 29, 2009.
  18. "Tropical Depression 10W (Etau) Advisory Eighteen (Final)". Joint Typhoon Warning Center. August 12, 2009. Retrieved August 29, 2009.
  19. "WWJP25 RJTD 130600". Japan Meteorological Agency. August 13, 2009. Retrieved August 29, 2009.
  20. "WWJP25 RJTD 140000". Japan Meteorological Agency. August 14, 2009. Retrieved August 29, 2009.
  21. Medhi Chebil (August 10, 2009). "China 'over the worst' as deadly storm heads for Japan". France 24 International News. Archived from the original on August 12, 2009. Retrieved August 10, 2009.
  22. Staff Writer (August 10, 2009). "At least nine killed as typhoon hits Japan". Belfast Telegraph. Retrieved August 10, 2009.
  23. Shingo Ito (August 10, 2009). "13 dead as typhoon brings floods, landslides to Japan". Agence France-Presse. Archived from the original on August 13, 2009. Retrieved August 10, 2009.{{cite web}}: CS1 maint: unfit URL (link)
  24. Staff Writer (August 10, 2009). "13 die due to typhoon-triggered heavy rain in western Japan". Japan Times. Archived from the original on August 10, 2009. Retrieved August 10, 2009.{{cite news}}: CS1 maint: unfit URL (link)
  25. Staff Writer (August 10, 2009). "Twenty-eight dead as typhoons hit East Asia". Agence France-Presse. Archived from the original on August 13, 2009.{{cite web}}: CS1 maint: unfit URL (link)
  26. Shino Yuasa (August 10, 2009). "12 killed, 10 missing as typhoon hits Japan". Ledger-Enquirer. Archived from the original on August 10, 2009. Retrieved August 10, 2009.
  27. "Four dead as typhoon brings heavy rain to Japan". Hindustan Times. Agence France-Presse. August 10, 2009. Archived from the original on August 14, 2009. Retrieved August 10, 2009.{{cite news}}: CS1 maint: unfit URL (link)
  28. Staff Writer (August 10, 2009). "Deaths as typhoon pounds Japan". Al Jazeera. Archived from the original on August 13, 2009. Retrieved August 10, 2009.{{cite web}}: CS1 maint: unfit URL (link)
  29. Sam Yeh (August 11, 2009). "Typhoons pound East Asia, 61 dead". Agence France-Presse. Archived from the original on August 11, 2009. Retrieved August 11, 2009.{{cite web}}: CS1 maint: unfit URL (link)
  30. "At Least 1,000 Found Alive After Typhoon Hits Taiwan". Fox News. Associated Press. August 12, 2009. Archived from the original on August 15, 2009. Retrieved August 12, 2009.{{cite web}}: CS1 maint: unfit URL (link)
  31. "Japanese troops join in typhoon rescue". Asia One News. Agence France-Presse. August 11, 2009. Archived from the original on August 16, 2009. Retrieved August 14, 2009.
  32. Staff Writer (August 11, 2009). 2009年8月台風9号(台風0909号)豪雨災害 研究関係情報 (in Japanese). 静岡大学防災総合センタ. Retrieved August 11, 2009.
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