2011 Pacific typhoon season

2011 Pacific typhoon season
Season summary map
Seasonal boundaries
First system formed	April 1, 2011
Last system dissipated	January 1, 2012
Strongest storm
Name	Songda
• Maximum winds	195 km/h (120 mph) (10-minute sustained)
• Lowest pressure	920 hPa (mbar)
Seasonal statistics
Total depressions	40
Total storms	21
Typhoons	8
Super typhoons	4 (Unofficial)
Total fatalities	1800 total
Total damage	> $4.905 billion (2011 USD)

The 2011 Pacific typhoon season was the time of the year in which tropical cyclones form in the Western Pacific Ocean. The season ran throughout 2011 with most tropical cyclones forming between May and November. The scope of this article is limited to the Pacific Ocean to the north of the equator between 100th meridian east and the 180th meridian. Within the Northwestern Pacific Ocean, there are two separate agencies who assign names to tropical cyclones which can often result in a cyclone having two names. The Japan Meteorological Agency will name a tropical cyclone should it be judged to have 10-minute sustained wind speeds of at least 65 km/h, (40 mph) anywhere in the basin. Whilst the Philippine Atmospheric, Geophysical and Astronomical Services Administration assigns names to tropical cyclones which move into or form as a tropical depression in their area of responsibility located between 135°E and 115°E and between 5°N-25°N even if the cyclone has had a name assigned to it by the Japan Meteorological Agency. Tropical depressions that are monitored by the United States' Joint Typhoon Warning Center are given a number with a "W" suffix.

Seasonal forecasts

Forecast Center	Date	Total TCs	Tropical storms	Total Typhoons	Intense TCs	Source
GCACIC	Average (1950–2000)	31	27	17	–
TSR	Average(1965–2010)	–	26.3	16.4	8.5
TSR	March 8, 2011	–	27.8	17.5	7.8
TSR	May 5, 2011	–	28.0	17.7	7.6
GCACIC	May 9, 2011	31	27	16	–
CWB	June 28, 2011	–	22–26	–	–
GCACIC	July 4, 2011	31	27	17	–
TSR	July 4, 2011	–	28.3	18.1	8.4
TSR	August 5, 2011	–	28.2	17.9	8.0
JMA	Actual activity	39	21	8	–
JTWC	Actual activity	27	18	10	–

During each season several national meteorological services and scientific agencies forecast how many tropical cyclones, tropical storms, and typhoons will form during a season and/or how many tropical cyclones will affect a particular country.

City University of Hong Kong

During 2011, the Guy Carpenter Asia-Pacific Climate Impact Centre (GCACIC), of the City University of Hong Kong (CityUHK), issued two forecasts of activity in April and June for the region. In each forecast they predicted how many tropical cyclones were going to exist during the season, how many would make landfall on Southern China and how many would pass within 100 km (62 mi) of the Korean Peninsula or Japan.

Number of tropical cyclones

Since 2000 the GCACIC, have predicted how many tropical cyclones will develop during the season and how many of which will intensify further into tropical storms and typhoons. During April, the GCACIC predicted that an average amount of 31 tropical cyclones would develop during the season and predicted that 27 of these cyclones would intensify into tropical storms while 17 would develop further into typhoons. In June the GCACIC reported that they had lowered their prediction for the number of tropical storms developing into a typhoon by 1 because of the strength of the India-Burma trough.

Southern China

Since 2009 the GCACIC have predicted how many tropical cyclones will make landfall on the Southern China coast between May and August as well as between September and December. The GCAIC also provided an overall total of how many tropical cyclones are expected to make landfall between May and December and during the main part of the season between July and December. In April they predicted that seven tropical cyclones would make landfall on the Southern China coast, between May and December compared with an average of five. Five were meant to make landfall on the area, between May and August, while an average amount of 2 tropical cyclones, were predicted to make landfall during the later part of the season. In their July update the GCACIC reported that seven tropical cyclones were predicted to make landfall on the region during the main part of the season between July and December.

Japan and Korea region

Since 2010 the GCACIC have predicted how many tropical cyclones would pass within 100 km (62 mi) of the Korean Peninsula or Japan during the whole season and the main part of the season between July and December. In April they predicted that the region would see 6 tropical cyclones during the whole year compared to an average of 4 tropical cyclones. In June, they predicted that the region would see 7 tropical cyclones during the main part of the season compared to an average of 3.

Tropical Storm Risk Consortium

Since the 2000 Pacific typhoon season, the Tropical Storm Risk Consortium (TSR) of University College London have issued forecasts of activity for each upcoming typhoon season. Forecasts on the number of tropical storms, typhoons and intense typhoons there would be during 2011 in the Western Pacific were released in March, May, July and August. In all off their forecasts this year, TSR predicted that the season would see activity close to the average with 28 tropical storms, 18 typhoons and 8 intense typhoons developing during the season.

National meteorological service predictions

On January 17, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) reported that they were expecting between 20 and 22 tropical cyclones to pass through the Philippine area of responsibility during 2011. On March 23 the Hong Kong Observatory (HKO), reported that they had predicted that 6-9 tropical cyclones would affect Hong Kong during the season. On April 26, the Thai Meteorological Department predicted that 2 tropical storms would affect Thailand during 2011. They predicted that 1 would move through Vietnam and affect Upper Thailand, during August or September. While the second tropical storm was expected to move through Southern Thailand during October or November. On June 30, Taiwan's Central Weather Bureau predicted that the 2011 season would be near its normal climatic average of 25.7, and predicted that 22-26 tropical storms, would occur over the Western Pacific during 2011, with 3 to 5 of them affecting Taiwan.

Seasonal summary

During April two tropical depressions developed but they failed to intensify into tropical storms. Tropical Storm Aere (Bebeng) then developed on May 5, and after causing PHP 2.25 billion in damage to Northeastern Luzon and Eastern Visayas, the name Bebeng was retired by PAGASA. The second tropical storm of the season then developed on May 19 and affected the Philippines, Taiwan and Japan before becoming extratropical to the east of Japan.

Systems

Tropical Depression 01W

Tropical depression (JMA)
Tropical depression (SSHWS)
Duration	April 1 – April 4
Peak intensity	55 km/h (35 mph) (10-min); 1004 hPa (mbar)

On April 1, the Japan Meteorological Agency (JMA) and Joint Typhoon Warning Center (JTWC) began monitoring an area of low pressure associated with intermittent convection over the South China Sea, roughly 535 km (332 mi) east-southeast of Ho Chi Minh City, Vietnam. The former of these two agencies immediately declared the system a tropical depression, the first of the 2011 season. Following further development of the system, most notably convective banding around the low-level circulation center, the JTWC issued a Tropical Cyclone Formation Alert on the storm. Early on April 2, the agency followed through with this alert and designated the low as Tropical Depression 01W. However, within hours of this, the depression became devoid of convection as wind shear buffeted the system. This prevented the cyclone from intensifying beyond depression status as it remained nearly stationary. Failing to regain convection by April 3, the depression degenerated into a remnant low and the final advisory from the JTWC was issued. The JMA continued to monitor the system as a tropical depression for another day before issuing their last warning on the system.

Tropical Depression 02W (Amang)

Tropical depression (JMA)
Tropical depression (SSHWS)
Duration	April 3 – April 6
Peak intensity	55 km/h (35 mph) (10-min); 1000 hPa (mbar)

On March 30, the JMA began monitoring an area of low pressure located southwest of Yap. By April 2, the system developed a low-level circulation, though convection appeared disorganized. Exhibiting good outflow within a region of weak wind shear, the low was anticipated to develop further over the following several days as it drifted west-northwestward. After briefly stalling early on April 3, the storm turned towards the east. Additionally, the JMA considered the system sufficiently organized to be declared a tropical depression. As the system was located to the west of 135°E, PAGASA began issuing advisories on the depression as well, assigning it the name "Amang". Tracking northeastward, the depression eventually developed enough convection to be declared Tropical Depression 02W by the JTWC on April 4. However, this was expected to be brief as a decaying frontal boundary approached from the west and prompted the system to undergo an extratropical transition. This intensification prompted the National Weather Service (NWS) in Tiyan, Guam to issue a tropical storm warning for the islands of Agrihan, Pagan and Alamagan. Interacting with the front and high wind shear, the system became partially exposed and elongated as it moved over cooler waters. Early on April 6, the JTWC issued their final advisory on the depression as it began to dissipate over open waters. Following degradation of the storm's structure, the NWS discontinued warnings for the Mariana Islands on April 6. The JMA continued to monitor the system for several more hours before ceasing advisories on it as well.

Tropical Storm Aere (Bebeng)

Main article: Tropical Storm Aere (2011)

Tropical storm (JMA)
Tropical storm (SSHWS)
Duration	May 5 – May 12
Peak intensity	75 km/h (45 mph) (10-min); 992 hPa (mbar)

Early of May 4, an area of low pressure formed about 140 km (87 mi) to the west of Palau Island. On that same day, the low pressure starts to strengthen rapidly with improved LLCC, tightly–wrapped shallow convective banding and a well–defined center. On the next day the low pressure starts to move northwest in general direction to the seas east of Philippine Islands. However it remained almost stationary by afternoon due to the influence of high pressure that located in the northeast of the system. By that time, its LLCC starts to become elongated and the system was also located in favorable sea surface temperatures with low vertical wind shear. Later of that day, its LLCC starts to consolidate again and the system starts to move northwest slowly, whilst the Japan Meteorological Agency upgraded the system into a tropical depression In the afternoon of May 6, Joint Typhoon Warning Center upgraded the low pressure into a tropical depression. In the same evening, PAGASA upgraded the low pressure into a tropical depression and assigned its local name 'Bebeng'. In the afternoon of May 7, JMA upgraded the tropical depression to a tropical storm, and assigned the name 'Aere'. During the early morning of May 12, the JMA downgraded Aere to a tropical depression while south of Kyushu Island.

Throughout the Philippines, multiple agencies activated their emergency plans as the storm approached. The Armed Forces of the Philippines, the Philippine National Police, and the Philippine Coast Guard were all placed on standby to deploy to areas struck by Aere once the storm passed. Several ports were affected by the storm, stranding 1,379 passengers by the afternoon of May 7. According to the National Disaster Risk Reduction and Management Council, at least 35 people have been killed and two more are missing as a result of Aere. Agricultural losses are estimated at PHP1.37 billion (US$31.7 million). Widespread flooding and landslides damaged homes, blocked off roads and severed communications. In Catarman, Northern Samar, 377.4 mm (14.86 in) of rain fell in just 24 hours, resulted in significant flash flooding.

Typhoon Songda (Chedeng)

Violent typhoon (JMA)
Category 5 super typhoon (SSHWS)
Duration	May 19 – May 29
Peak intensity	195 km/h (120 mph) (10-min); 920 hPa (mbar)

On May 19, the JTWC reported that an area of low pressure had persisted about 510 km (320 mi) to the southeast of Yap. As the system moved towards the northwest under the influence of a subtropical ridge of high pressure, it rapidly consolidated in an area of light to moderate vertical windshear. The JMA then started to monitor the system as a tropical depression later that day, before the JTWC designated it as Tropical Depression 04W early on May 20. The JTWC then reported later that day that the depression had intensified into a tropical storm with windspeeds of 65 km/h (40 mph), however it later reported that it had overestimated the windspeeds and consequently lowered the storm's status to a tropical depression, based on observations from Yap island. Late on May 21, both the JMA and the JTWC reported that the depression had now become a tropical storm with the JMA naming it as Songda. Over the next couple of days, the system gradually intensified further while moving northwest into PAGASA's area of responsibility. PAGASA named it as Chedeng. At 1200  UTC on May 24, the JTWC reported that Songda had intensified into a typhoon. 12 hours later the JMA followed suit while the system was located about 800 km (500 mi) to the southeast of Manila in the Philippines. It rapidly intensified into a Category 5 typhoon. In the afternoon of May 29, Songda became extratropical south of Shikoku Island.

Although Songda remained offshore, heavy rains within the typhoon's outer bands impacted the Philippines, causing significant flash flooding and landslides. Four fatalities are attributed to the system there. Further north, Okinawa experience intense wind gusts, measured up to 198 km/h (123 mph), along with torrential rain. Extensive damage took place across the area with losses reaching ¥23.2 billion ($287 million); however, there were no fatalities. As it became extratropical, Songda brought heavy rains from Kyushu to eastern Honshu, causing significant flooding. At least 13 people were killed in the country and an estimated 400,000 had to be evacuated around Tokyo alone.

Tropical Depression

Tropical depression (JMA)
Duration	May 31 – June 2
Peak intensity	<55 km/h (35 mph) (10-min); 1004 hPa (mbar)

On May 30, the JTWC started to monitor a low level circulation centre that had formed at the southern end of a shear line, about 400 km (250 mi) to the southeast of Manila in the Philippines. During that day the system rapidly moved towards the north-northeast, before the JMA reported that the system had developed into a tropical depression, while it was located about 420 km, {260 mi) to the southeast of Hong Kong in China. However as it continued to move towards the north-northeast, a short-wave trough of low pressure located over Hainan island and dry cold air wrapping into the circulation inhabited further development of the low level circulation centre. The JMA then reported during the next day that the depression had weakened into an area of low pressure before the JTWC reported that the depression had dissipated.

Tropical Storm Sarika (Dodong)

Tropical storm (JMA)
Tropical depression (SSHWS)
Duration	June 8 – June 11
Peak intensity	75 km/h (45 mph) (10-min); 996 hPa (mbar)

On early June 8, an area of low pressure formed about 10 km west of Cebu City, Philippines. As it moved towards the Mindoro Strait the JMA and JTWC began to monitor the system. In the early morning hours of June 9, the Philippines' PAGASA upgraded the system to a tropical depression and reported the storm center to be about 450 km west of Dagupan City in the Philippines. The next day, the JMA and JTWC upgraded the tropical depression into a tropical storm, with the JMA naming it Sarika. During the morning of June 11 the JTWC downgraded Sarika to a tropical depression after making landfall in Shantou, China. The JTWC soon issued their final advisory on Sarika. Sarika made landfall on mainland China with winds of 75 km/h (45 mph). As a result of the storm, 23 people were killed in Xianning, and ten more were declared missing. Damages from Sarika are estimated at $248 million.

Tropical Depression

Tropical depression (JMA)
Duration	June 15 – June 16
Peak intensity	<55 km/h (35 mph) (10-min); 1004 hPa (mbar)

Early June 15 an area of low pressure area embedded along the Intertropical Convergence Zone located about 250 km west of Puerto Princesa, Palawan. As is moved towards the South China Sea, both the JMA and the JTWC started monitoring it. During the morning of June 15, the JMA upgraded it into a tropical depression. Due to an anticyclone, the system dissipated during the early morning of June 16,as it made landfall in Hong Kong.

Tropical Storm Haima (Egay)

Tropical storm (JMA)
Tropical storm (SSHWS)
Duration	June 16 – June 25
Peak intensity	75 km/h (45 mph) (10-min); 985 hPa (mbar)

On June 15, the JTWC started to monitor an area of disturbed weather that was located about 1,350 km (840 mi), to the southeast of Manila, Philippines. Over the next couple of days the system gradually developed further, before late on June 16, the JMA, JTWC and PAGASA, all reported that the system had developed into a tropical depression, with PAGASA naming it as Egay. Egay continued to develop during June 17 as it moved towards the northeast, and on June 18 the JTWC reported that Egay had intensified into a tropical storm. Late on June 19, the JTWC downgraded Egay to a tropical depression, but they upgraded Egay again to a tropical storm on June 20. Early on June 20, the JTWC downgraded Egay to a tropical depression again. On June 21, the JMA upgraded the system into a tropical storm and named it Haima, with the JTWC following suit on June 22.As the system started to reintensify it developed a rare case of having two low level circulation centers due to earlier land land interaction which later merged and allow haima to intensify so the JMA upgraded the system into a tropical storm and named it Haima, with the JTWC following suit on June 22.

During the evening of June 23, the JTWC downgraded Haima to a tropical depression after making landfall in Zhanjiang, Guangdong, China but upgraded it to a tropical storm again on June 24. Early on June 25, Haima became a tropical depression after moving inland in Vietnam. As it made landfall over Hanoi, Vietnam, the JTWC and the Hong Kong Observatory downgraded Haima to a low pressure area.

Severe Tropical Storm Meari (Falcon)

Severe tropical storm (JMA)
Tropical storm (SSHWS)
Duration	June 20 – June 27
Peak intensity	110 km/h (70 mph) (10-min); 975 hPa (mbar)

Early on June 20, and area of low pressure about 760 km (470 mi), east of the Philippines began to be monitored by both the JTWC and JMA. That evening, the JTWC issued a Tropical Cyclone Formation Alert. Soon afterwards, PAGASA upgraded the system into a tropical depression, naming it as "Falcon". At the time of the upgrade, Falcon was located about 1,000 km (620 mi), east northeast of Cebu City. During the evening of June 21, the JTWC also reported that Falcon had strengthened into a tropical depression. On June 22, both the JTWC and the JMA upgraded Falcon into a tropical storm, and the JMA named it Meari. Meari leaves Philippines with 2 deaths and 5 missing. In the afternoon on June 24, the JMA upgraded Meari to a severe tropical storm as it passed Okinawa, Japan.

On June 26, Meari rapidly moved to the Yellow Sea but slowly passed Weihai, Shandong, China, and then the JMA downgraded Meari to a tropical storm on the same day. On June 27, the JTWC downgraded Meari to a tropical depression before it made landfall in North Korea, and the JMA reported that Meari became a low pressure area later.

Heavy rains from the storm's outer bands triggered significant flooding and landslides in South Korea. At least nine people were killed and three others were reported missing across the country. In North Korea, heavy rains from the storm caused widespread flooding and damage. At least 160 homes were destroyed and 50,000 hectares of crops submerged. Several reports of confirmed fatalities arose but no details on how many were given to news agencies.

Tropical Depression (Goring)

Tropical depression (JMA)
Duration	July 9 – July 10
Peak intensity	55 km/h (35 mph) (10-min); 1000 hPa (mbar)

Late July 9 an area of low pressure area formed about 300 km (190 mi) east of Aurora as it moves Northwest it has been located 500 km (310 mi) east-southeast of Basco, Batanes. On the morning of July 9, JMA upgraded the low pressure area into a tropical depression and it was located 450 km northeast of Cagayan. In the afternoon, PAGASA upgraded the low pressure area into a tropical depression and named it Goring. After moving to Fujian, China, it dissipated on the evening on July 10.

Typhoon Ma-on (Ineng)

Main article: Typhoon Ma-on (2011)

Very strong typhoon (JMA)
Category 4 typhoon (SSHWS)
Duration	July 11 – July 24
Peak intensity	175 km/h (110 mph) (10-min); 935 hPa (mbar)

On July 11, both the JMA and JTWC upgraded a tropical disturbance to a tropical depression which was located near Minamitorishima. On July 12, both the JMA and JTWC upgraded the system to a tropical storm and named it Ma-on. Early on July 13, the JMA upgraded Ma-on to a severe tropical storm. Late on July 13, both the JMA and the JTWC upgraded Ma-on to a typhoon. After absorbing Tokage, Ma-on reached its peak strength on July 16. The PAGASA named it Ineng on July 17.

As Ma-on was affecting Japan, the JTWC downgraded it to a tropical storm in the evening on July 19. Ma-on made landfall in Tokushima later. The JMA downgraded Ma-on to a severe tropical storm after it made landfall in Wakayama early on July 20. The JTWC downgraded Ma-on to a tropical depression on July 21 and discontinued advisories the following day. The JMA downgraded Ma-on to a tropical storm early on July 23. On July 24, Ma-on weakened into an extratropical cyclone east of the Tōhoku region.

Tropical Storm Tokage (Hanna)

Tropical storm (JMA)
Tropical depression (SSHWS)
Duration	July 13 – July 16
Peak intensity	65 km/h (40 mph) (10-min); 1000 hPa (mbar)

On July 11, the JTWC started to monitor a tropical disturbance that had developed within a poorly organized monsoon trough about 1,000 kilometres (620 mi) to the northwest of Hagatna, Guam. Over the next couple of days, the disturbance moved towards the west and despite the system being in an area of low vertical windshear, deep convection surrounding the system struggled to organize around the disturbances low level circulation centre. However by 0600UTC on July 13 it had organized enough for the Japan Meteorological Agency to declare the disturbance a tropical depression. Over the next two days the system continued to move towards the west and gradually consolidated further. The JMA then named the system as Tokage, as it had developed into a tropical storm and reached its 10-minute peak wind speeds of 65 km/h (40 mph). PAGASA then initated advisories on the system and named it Hanna, before the JTWC designated the system as Tropical Depression 09W and initiated advisories on the system, while it was at its 1-minute peak wind speeds of 55 km/h (35 mph). However by this time Tokage was already interacting with Typhoon Ma-on, with Ma-on's outflow causing convection not to develop over the centre and generally weaken the system. The JMA, PAGASA and the JTWC then issued their final advisories on the system later that day as Tokage dissipated.

Tropical Depression

Tropical depression (JMA)
Duration	July 16 – July 17
Peak intensity	<55 km/h (35 mph) (10-min); 998 hPa (mbar)

Originally a low pressure area, the JMA reported that a tropical depression formed from it inland in Guangdong, China on July 16. On July 17, the depression dissipated.

Tropical Depression

Tropical depression (JMA)
Duration	July 16 – July 16
Peak intensity	<55 km/h (35 mph) (10-min); 1002 hPa (mbar)

Originally a low pressure area, the JMA reported that a tropical depression formed from it in the Gulf of Tonkin near Guangdong, China on July 16. However, it quickly dissipated after only six hours.

Severe Tropical Storm Nock-ten (Juaning)

Main article: Tropical Storm Nock-ten (2011)

Severe tropical storm (JMA)
Category 1 typhoon (SSHWS)
Duration	July 24 – July 31
Peak intensity	95 km/h (60 mph) (10-min); 985 hPa (mbar)

Early on July 22, an area of low pressure formed to the east of Philippines. The system gradually drifted west over the next few days and late on July 24, the Joint Typhoon Warning Center Started Monitoring the system as a Tropical Depression. Early the next day, the Japan Meteorological Agency (JMA) upgraded the area of low pressure into a Tropical Depression. A few hours later, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) started monitoring the system as a Tropical Depression and named it 'Juaning'. The system continued to drift westwards and strengthened rapidly, that on midnight, that day, the JMA further upgraded the system into a Tropical Storm, naming it Nock-Ten. Early on July 27, the JMA reported that Nock-ten continued to strengthen and upgraded it into a Severe Tropical Storm. A few hours later, the JTWC reported that Nock-ten rapidly intensified to a category 1 typhoon and made its landfall over northern Aurora (province) and started weakening. Later the same day, the JMA reported that Nock-ten has exited the Luzon island at Candon maintaining severe tropical storm strength. However, overnight, the storm rapidly weakened and the JMA downgraded it into a minor tropical storm the next day. However, on July 29, the storm gradually regained strength and approached south China coast at Qionghai, China. Later that day, the storm strengthened over land and headed north towards Hainan's provincial capital region Haikou. Over the next day, the storm drifted to the west and made landfall over Northern Vietnam. The storm weakened rapidly and at midnight that day, the JMA, issuing their final warning on the system, downgraded it into a tropical low.

The provinces of Albay and Camarines were reported to be completely flooded by the rain. Minor damage to rice crops was reported. More heavier rains were expected throughout the day as the system has exited land into south china sea and will soon start reintensifying. The number of missing was also pushed up to 31 after 25 crewmembers of a fishing boat were reported missing when their fishing boat was caught in the storm off Masbate. Nock-ten suspended all classes in Luzon from Pre-school to college levels on July 26 and 27. In Northern Luzon, Nock-ten poured down heavy rainfall becoming widespread flooding in the area. The national roads were impassable and landslides were also reported. About 26 domestic flights were cancelled from July 26 to 27 due to heavy rains and strong winds.

Typhoon Muifa (Kabayan)

Main article: Typhoon Muifa (2011)

Very strong typhoon (JMA)
Category 5 super typhoon (SSHWS)
Duration	July 25 – August 9
Peak intensity	175 km/h (110 mph) (10-min); 930 hPa (mbar)

Late on July 23, an area of low pressure formed to the southeast of Chuuk. the system gradually drifted to the west and on July 25, the JTWC upgraded the low pressure area to a tropical depression. At that time, it was located approximately 505 nautical miles (935 km; 581 mi) to the west of Guam. At midnight, that day, the JMA started monitoring the system as a tropical depression. Early on July 28, the JTWC upgraded the system into a Tropical Storm. A few hours later, the JMA too upgraded the system to a tropical storm, naming it Muifa. Soon, the storm moved into the Philippine Area of Responsibility (PAR) and the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) named it Kabayan. The storm gradually drifted north over the next day maintaining strength. On the night of July 29, Muifa was upgraded into a Severe Tropical Storm. Overnight, the storm strengthened rapidly and was upgraded into a Typhoon the next morning. The storm strengthened so rapidly, and the JTWC reported that the storm's peak winds were reaching 140 knots (260 km/h; 160 mph) (1-min sustained), as it strengthened into a Category 5 Typhoon. However, the typhoon couldn't maintain Category 5 strength for a long time. According to the JTWC, On July 31, the typhoon interacted with an upper level trough and weakened into a Category 4 Typhoon on the SSHS. The system gradually moved north, then turned west and drifted towards Okinawa, before turning northwest again, when it was finally downgraded into a Tropical Storm by the JTWC. Soon afterwards, the JMA too downgraded Muifa to a Severe Tropical storm. After weakening to a tropical storm, Muifa made landfall at the estuary of the Yalu River on August 8, and the JTWC issued the final warning. Early on August 9, Muifa weakened to a tropical depression in Northeast China and became a low pressure area later.

Muifa killed 2 men, as their boat was capsized in the vicinity of Hagonoy, Bulacan and Pampanga Delta. Due to the southwest monsoon enhanced by Muifa, it caused heavy rains in several parts of Luzon including Metro Manila. Early of August 2, the Malacañang Palace suspended government offices and Pre-school to college level in NCR. Nearby provinces like Calabarzon (Region IV-A) also suspended their classes. In Marikina 200 residents or 31 families living in communities along the Marikina River have sought shelter in evacuation centers.

Tropical Depression Lando

Tropical depression (JMA)
Duration	July 31 – August 2
Peak intensity	<55 km/h (35 mph) (10-min); 1002 hPa (mbar)

On July 31, the JMA reported that a tropical depression had developed about 500 km (315 mi) to the north west of Manila in the Philippines. However because of the outflow from Typhoon Mufia, the deep convection that surrounded the system was being sheared off to the west of the systems low level circulation centre. During that day the depression moved towards the north slowly, before PAGASA named it as Lando, however during the next day they reported that the depression had weakened into a low pressure area and released their final advisory on it. After PAGASA issued their final advisory, the JMA continued to monitor the depression for another 24 hours before late on July 2, the JMA dropped the system from their advisories as it dissipated. According to PAGASA, Lando did not directly affect the Philippines, however instead it enhanced the south west monsoon which brought widespread rains to Luzon and Visayas.

Severe Tropical Storm Merbok

Severe tropical storm (JMA)
Category 1 typhoon (SSHWS)
Duration	August 3 – August 9
Peak intensity	95 km/h (60 mph) (10-min); 980 hPa (mbar)

Early on August 3, the Japan Meteorological Agency (JMA) upgraded an area of low pressure near Wake Island to a tropical depression. The system intensified rapidly and just 6 hours later, the JMA upgraded the system to a tropical storm, naming it Merbok. Soon, the Joint Typhoon Warning Center (JTWC) started monitoring the system as a tropical depression, and upgraded it to a tropical storm later. Merbok began to move westward slowly, but soon afterwards, it turned northwest and gradually drifted in that direction. Late on August 5, the JMA upgraded Merbok into a Severe Tropical Storm. Early on August 6, the JTWC upgraded Merbok into a Category 1 Typhoon 830 nautical miles (1,540 km; 960 mi) East-southeast of Tokyo, Japan. Early the next day, the storm's winds reached a peak of 80 knots (150 km/h; 92 mph) (1-min sustained) on the SSHS. Later that day, the system was caught in a moderate Vertical Wind Shear and started weakening. On August 8, the system started accelerating towards north at the speed of 20 knots (37 km/h; 23 mph) and was gradually diminishing because of colder and colder sea surface temperatures and unfavorable conditions. As a result, the JMA reporting that the system was no longer a Severe Tropical Storm, downgraded Merbok to a Tropical Storm. Late on that day, the system started showing extratropical characteristics as the convection near the eye dissipated rapidly. Thus, the JTWC issued their final warning on the system reporting that the system was no longer tropical. Later, the JMA, issuing their final warning on the system, reported that the system was no longer tropical.

Tropical Depression

Tropical depression (JMA)
Duration	August 3 – August 4
Peak intensity	55 km/h (35 mph) (10-min); 1008 hPa (mbar)

Early on August 3, a tropical depression formed near the Bonin Islands. The system slowly began to track northwestwards, towards Japan. Late on August 4, the system dissipated near the Kii Peninsula.

Tropical Depression 13W

Tropical depression (JMA)
Tropical depression (SSHWS)
Duration	August 8 – August 15
Peak intensity	55 km/h (35 mph) (10-min); 1004 hPa (mbar)

Late on August 8, the JMA upgraded a low pressure area to a tropical depression west of Guam, and the JTWC issued a TCFA. The system gradually drifted north and early on August 10, the JTWC started monitoring the system as a tropical depression and designated it with 13W. Initially, the JMA predicted the system to strengthen into a tropical storm, but on August 11, as it moved further north into cool waters and experienced unfavourable conditions, the JMA issued their final advisory. Later, the JTWC too issued their final warning on the system, reporting that it has moved into a subtropical ridge and was expected to dissipate into a remnant low. However, the JMA continued to track the remants as a weak tropical depression over the next few days until the system dissipated on August 15.

Tropical Depression

Tropical depression (JMA)
Duration	August 8 – August 10
Peak intensity	55 km/h (35 mph) (10-min); 1008 hPa (mbar)

Late on August 8, the JMA upgraded an area of low pressure to a tropical depression, to the northwest of Minamitorishima. The system gradually moved to the northeast. On August 10, the system was caught in a moderate vertical wind shear and due to cold sea surface temperature, the system dissipated into a remnant low.

Tropical Depression

Tropical depression (JMA)
Duration	August 20 – August 25
Peak intensity	55 km/h (35 mph) (10-min); 1002 hPa (mbar)

On August 19, a low pressure area developed east-northeast of Guam. Early on August 20, the system developed a broad area of low level circulation center and a good divergence aloft becoming more well defined. Later that day, the JMA upgraded the system to a tropical depression southeast of the Bonin Islands. On August 22, the system started interacting with an anticyclone and was exposed to a strong vertical wind shear, prompting the JMA to stop monitoring the system as a tropical depression, as the system dissipated to a remnant low. However, at midnight, the same day, the remnants regenerated, and the JMA started tracking the system as a tropical depression again, until it last appeared near Okinawa, Japan on August 25, as the system dissipated completely.

Typhoon Nanmadol (Mina)

Main article: Typhoon Nanmadol (2011)

Very strong typhoon (JMA)
Category 5 super typhoon (SSHWS)
Duration	August 21 – August 31
Peak intensity	185 km/h (115 mph) (10-min); 925 hPa (mbar)

Late on August 19, an area of low pressure developed north of Palau. Early on August 20, the system became more better organized and developed a low-level circulation center. The system then turned north and continued to drift north until on August 21, when the JMA upgraded the low pressure area to a tropical depression east of Philippines. The JTWC also issued a Tropical Cyclone Formation Alert (TCFA) on the system reporting that the system was becoming more well organized. Later that day, the PAGASA started monitoring the system as a tropical depression and named it Mina. Late on August 22, the system became more well organized prompting the JTWC to initiate advisories on the system, designating it with 14W. On August 23, the JMA upgraded 14W to a tropical storm, naming it Nanmadol. Overnight, the system continued to intensify and early on August 24, the JMA upgraded Nanmadol to a severe tropical storm. Later that day, convective banding improved and Nanmadol developed an eye-like feature. As a result, Nanmadol continued to intensify rapidly and became a typhoon, by midnight, that day. Nanmadol continued to drift north east and made landfall over Gonzaga, Cagayan, Philippines with strong winds of over 95 knots (176 km/h; 109 mph). Nanmadol weakened significantly after interacting with land and early on August 28, the JMA downgraded Nanmadol to a severe tropical storm. Late on August 28, Nanmadol made its second landfall over Taimali in the Taitung County of Taiwan and started weakening. Landfall weakened the system rapidly prompting the JMA to downgrade Nanmadol to a tropical storm with winds of under 45 knots (83 km/h; 52 mph). Soon it started experiencing strong wind shear and continued weakening. The shear pushed convection approximately 70 knots (130 km/h; 81 mph) south of the LLCC. The system also accelerated towards China at 8 knots (15 km/h; 9.2 mph) and weakened to a minimal tropical storm. After its third landfall over Fujian, China, Nanmadol weakened rapidly prompting both the JTWC and the JMA to issue their final warnings on the system.

On August 27, five people died after Nanmadol caused landslides. At least two Filipino fishermen were reported to be missing after Nanmadol's strong winds whipped up large waves.

Severe Tropical Storm Talas

Main article: Tropical Storm Talas (2011)

Severe tropical storm (JMA)
Tropical storm (SSHWS)
Duration	August 23 – September 5
Peak intensity	95 km/h (60 mph) (10-min); 970 hPa (mbar)

Late on August 22, a low pressure area developed to the west of Guam. At midnight that day, the system became sufficiently well organized that the JMA started tracking it as a tropical depression. On August 23, the system moved into an environment of low wind shear and warm sea surface temperatures prompting the JTWC to issued a TCFA on it. By August 25, the system grew strong enough that the JMA upgraded it to a tropical storm, naming it Talas. Later that day, the JTWC followed suit and initiated advisories on Talas. Talas continued to strengthen and by midnight that day, it became a severe tropical storm. Over the next few days, Talas continued to drift north very slowly until late on August 29, when the JMA upgraded Talas to a typhoon. Soon, a subtropical ridge to the west of the storm weakened and the subtropical ridge to the east of the system pushed Talas to the west. As a result, Talas accelerated towards the west maintaining strength and outflow. An upper-level cyclone over the system suppressed the convection and kept it from reaching the center. Therefore, Talas remained weak and did not strengthen further. Convection never managed to consolidate the center and convective banding remained well away from the fully exposed low-level circulation center. The convective banding continued to expand more and more with the outer rainbands already brushing parts of Japan. Coastal areas in the nation have already reported gale force winds several hours before landfall, while the Omega block continued to drive Talas towards the nation. Land interaction weakened Talas, prompting the JMA to downgrade Talas from a typhoon to a severe tropical storm with winds of under 60 knots (110 km/h; 69 mph). Early on September 3, Talas made landfall over Aki, Japan. After landfall, Talas accelerated north at over 13 knots (24 km/h; 15 mph) and its central convection became significantly eroded and was displaced to the north-east as Talas was exposed to a very strong wind shear of over 50 knots (93 km/h; 58 mph) that made the LLCC very distorted and difficult to pin-point. Talas was embedded in a baroclinic zone and the JTWC anticipated an extratropical transition, which prompted them to issue their final warning on the system. On September 5, the JMA issued their final warning on the system, reporting that Talas has become extratropical on the Sea of Japan.

Tropical Storm Noru

Tropical storm (JMA)
Tropical storm (SSHWS)
Duration	September 2 – September 6
Peak intensity	75 km/h (45 mph) (10-min); 990 hPa (mbar)

During September 1, the JTWC reported that a tropical disturbance had developed within the outflow of Tropical Storm Talas, about 980 km (610 mi) to the northeast of Hagåtña, Guam. Deep convection surrounded the systems low-level circulation but it was not organising as it was impacted, by a moderate to strong amount of vertical wind shear, which was produced by Tallas outflow and a TUTT cell to the northeast of the system. However, during that day vertical wind shear surrounding the system relaxed and the system started to consolidate, while it moved towards the north-northwest around a subtropical ridge of high pressure. Early the next day, because the system continued to consolidate the JTWC issued a tropical cyclone formation alert, while the JMA reported that the system had become a tropical depression. Over the next 24 hours, the system continued to consolidate as it moved towards the north-northwest before the JTWC initiated advisories on the system as it intensified into Tropical Storm 16W, however the JMA did not name it as Noru until 0600 UTC on September 4. As it was named, the JTWC reported that Noru had peaked with 1-minute windspeeds of 85 km/h (50 mph), while the JMA reported peak 10-minute sustained wind speeds of 75 km/h (45 mph). On September 5, after it had peaked in intensity, a fresh Tutt cell developed over the system and started to inhibit outflow and shear the convection away, which meant as a result that the system started to weaken. Over the next two days, Noru went through an extratropical transition before becoming an extratropical cyclone on September 6 about 1150 km (715 mi) to the northeast of Tokyo, Japan. As an extratropical cyclone, Noru continued its movement towards the north-northwest and affected Sakhalin and the Kuril Islands, before it moved over Okhotsk on September 9 and dissipated.

Tropical Storm Kulap (Nonoy)

Tropical storm (JMA)
Tropical storm (SSHWS)
Duration	September 6 – September 11
Peak intensity	65 km/h (40 mph) (10-min); 1000 hPa (mbar)

Late on September 4, an area of low pressure developed to the southeast of Okinawa, Japan. Over the next two days, the system drifted north and developed a well defined LLCC with organized convective banding, prompting the JMA to upgrade the low pressure area to a tropical depression. On September 7, convection consolidated the low-level circulation center very well with tightly curved banding wrapped into it. Also, high sea-surface temperatures and very low wind shear caused the system to undergo rapid deepening, prior to which, the JMA upgraded the system to a tropical storm and named it Kulap. However, the system stopped strengthening soon after as the LLCC became partially exposed and the convection was displaced to the south. Kulap remained small in size and dry air entering from the western periphery kept it from strengthening further. Wind shear increased, pushing convection approximately 180 nautical miles (330 km; 210 mi) south of the LLCC. Also, Kulap was located beneath a tropical upper tropospheric trough (TUTT cell) that caused subsidence. A mid-level subtropical steering ridge cuased Kulap to track in a northwestward direction. On September 8, Kulap moved into the east-northeast periphery of the Philippine Area of Responsibility (PAR) prompting the PAGASA to start issuing advisories on the system, naming it Nonoy. However, Kulap quickly accelerated north and exited the PAR on the same evening, prompting the PAGASA to issued their final advisory on the system. After increasing wind shear caused further weakening, the JTWC downgraded Kulap to a tropical depression late on September 8. Early on September 10, the JMA too downgraded Kulap to a tropical depression, and continued to track Kulap's remnants as a tropical depression until it was finally absorbed by the weather front early on September 11.

Typhoon Roke (Onyok)

Main article: Typhoon Roke (2011)

Very strong typhoon (JMA)
Category 4 typhoon (SSHWS)
Duration	September 11 – September 22
Peak intensity	155 km/h (100 mph) (10-min); 940 hPa (mbar)

Early on September 8, a cluster of thunderstorms came together as a low pressure area with imporoving outflow and a developing low-level circulation center (LLCC). Later that day, the JMA upgraded the low pressure area to a tropical depression north-northeast of the Northern Mariana Islands. Over the next two days, the system gradually drifted west and intensified slightly, prompting the JTWC to issue a Tropical Cyclone Formation Alert (TCFA) on it. Convection gradually consolidated the LLCC and the JTWC initiated advisories on the system on September 11, designating it with 18W. The next day, the depression drifted into the Philippine Area of Responsibility (PAR) and the PAGASA initiated advisories on the depression, naming it Onyok. However, just as similar to Kulap, Onyok also exited the PAR in 6 hours from entering the region. In an advisory, the JTWC reported that there were at-least two more vortices associated with the system, that caused an abrupt, erratic movement. However, being located in an area of warm sea surface temperatures and low vertical wind shear, the depression continued to strengthen and on September 13, the JMA upgraded the depression to a tropical storm and named it Roke. On September 17, Roke developed a small, deep convective eye promoting the JMA to upgrade Roke to a severe tropical storm with winds of over 50 knots (93 km/h; 58 mph). Between September 19 and 20, Roke underwent Explosive intensification, a more extreme case of rapid deepening that involves a tropical cyclone deepening at a rate of at least 2.5 mbar per hour for a minimum of 12 hours. Also, they added that Roke developed a 10 nautical miles (19 km; 12 mi) eye and a good poleward outflow channel. On September 21, Typhoon Roke made landfall over Hamamatsu, Japan at about 5:00 UTC (14:00 JST). Soon Roke started weakening as cloud tops started getting warmed up and eye diameter started to decrease. However, the system still maintained a near radial outflow and the convective structure continued to remain organized that kept Roke from dissipating rapidly. Although Roke entered a de-intensification phase, it still had plenty of strength that posed a great threat to regions of Japan. Being located approximately 330 nautical miles (610 km; 380 mi) southwest of Yokosuka, Kanagawa, the typhoon accelerated north-northwestward at approximately 16 knots (30 km/h; 18 mph) with winds of over 100 knots (190 km/h; 120 mph) (1-min sustained) being a Category 3 typhoon on the SSHS. Being embedded in the baroclinic zone, Roke started its extratropical transition. Also, land interaction severely weakened the storm to a minimal Category 1 typhoon with winds of under 70 knots (130 km/h; 81 mph) (1-min sustained). Only six hours later, the storm further weakened and accelerated northeastward at approximately 31 knots (57 km/h; 36 mph) with rapidly dissipating deep convection completely sheared to the northeast of the LLCC. As a result, the JTWC ceased advisories on the storm, as it became fully extratropical.

Typhoon Sonca

Typhoon (JMA)
Category 2 typhoon (SSHWS)
Duration	September 14 – September 20
Peak intensity	130 km/h (80 mph) (10-min); 970 hPa (mbar)

Early on September 13, a low pressure area formed northeast of the Northern Mariana Islands. The system gradually drifted north and steadily intensified until the next day when the JMA upgraded the system to a tropical depression. Later on September 14, the JTWC issued a Tropical Cyclone Formation Alert (TCFA) on the system reporting that the system could intensify into a tropical storm within 24 hours from then. Convection rapidly consolidated the center with persistent, deep convection around the north-eastern periphery, prompting the JTWC to initiate advisories on the system, designating it with 19W. Soon, the JMA also initiated advisories on the system, upgrading it to Tropical Storm Sonca. In the begging, Sonca seemed to have intensified rapidly since formation, however, soon the storm weakened back to a minimal tropical storm because of dry air entering the LLCC that caused it to elongate and weaken. However, that was not for too long as vigorous convection persisted over the well defined LLCC with tightly curved banding wrapped in, Sonca continued to strengthen gradually and the JTWC reported winds of at-least 50 knots (93 km/h; 58 mph) near the center. As Sonca continued to strengthen, and the JMA upgraded it to a severe tropical storm on September 17. Later that day, Sonca developed a large 10 nautical miles (19 km; 12 mi) ragged eye with deep convective banding tightly wrapped into it. As a result, Sonca strengthened more rapidly and by early the next day, it became a typhoon. On September 18, Sonca reached a peak intensity of 85 knots (157 km/h; 98 mph) (1-min mean) and 70 knots (130 km/h; 81 mph) (10-min mean) and soon the convection around the northern periphery started weakening. Being embedded in a baroclinic zone with low sea surface temperatures, Sonca started its extratropical transition late on September 19. The transition took place relatively fast because of a frontal boundary and the JTWC reported that Sonca became extratropical early on September 20, while the JMA did the same later in the evening.

Tropical Depression

Tropical depression (JMA)
Duration	September 14 – September 15
Peak intensity	<55 km/h (35 mph) (10-min); 1002 hPa (mbar)

Early on September 14, the JMA started monitoring a cluster of thunderstorms located to the southeast of Taiwan as a tropical depression. However, due to the Fujiwhara effect, the system could not strengthen, so the JMA stopped tracking the tropical depression late on September 15,due to the Fujiwhara effect,as the system was absorbed by Roke.

Typhoon Nesat (Pedring)

Main article: Typhoon Nesat (2011)

Typhoon (JMA)
Category 3 typhoon (SSHWS)
Duration	September 23 – September 30
Peak intensity	150 km/h (90 mph) (10-min); 950 hPa (mbar)

In the evening of September 21, a low pressure area developed to the east-southeast of Palau. The low gradually drifted west and became more well organized prompting the JTWC to issue a Tropical Cyclone Formation Alert (TCFA) on it. Later, the LLCC became well organized with flaring deep convection developing around it, so the JMA started monitoring the low as a tropical depression. Later on September 23, the JTWC also initiated advisories on the system designating it with 20W. Early on September 24, the JMA further upgraded 20W to a tropical storm and named it Nesat. Nesat continued to drift west with expanding deep convection around the entire system and consolidating convection around the LLCC. The mid-level warm anomaly near the system continued to intensify and convective banding near the LLCC became more and more tighter. As a result, the JMA upgraded Nesat to a severe tropical storm on September 25. Late on the same day, the JMA further upgraded Nesat to a typhoon. The system rapidly deepened and quickly developed a 30 nautical miles (56 km; 35 mi) ragged eye and mesoscale anticyclone aloft generating an exceptionally excellent all-around outflow. Also, the system had a highly symmetric radial outflow. The JTWC originally anticipated Nesat to become a category 4 typhoon on the SSHS with winds exceeding 130 knots (240 km/h; 150 mph) (1-min sustained). However, because of a cold anomaly, the system only reached a maximum 1-min sustained wind speed of 105 knots (194 km/h; 121 mph) making it a category 3 typhoon.

Early on September 27, Nesat made landfall over the Luzon region of Philippines. As a result, the eyewall got eroded and the maximum 1-min sustained winds dropped to 95 knots (176 km/h; 109 mph). The system approached land at nearly 10 knots (19 km/h; 12 mph). However, later on that day, the LLCC started to get re-consolidated with convection as Nesat quickly moved west and re-emerged over water. At that time, it was located near the southern periphery of a deep layered subtropical steering ridge and moved towards the southwest and the winds further dropped to 85 knots (157 km/h; 98 mph) because of land interaction. Though the system has maintained overall central deep convection, subsidence persisted along the northwest quadrant which caused further drop in wind speed. Upper level analysis indicated that Nesat was to the south of a ridge axis in an area of moderate vertical wind shear. The system continued to weaken with convective banding loosely wrapped into the partially exposed LLCC. The winds continued to drop and eventually reached 65 knots (120 km/h; 75 mph) (1-min sustained) which made it a minimal typhoon on the SSHS. Though the weakening, Water vapour imagery showed that the typhoon was still maintaining excellent outflow towards the equator and improving outflow towards the pole. Nesat maintained a relatively large area of gale force winds. Animated infrared satellite imagery depicted that the storm was expanding in size and convective banding continued to move further and further away from the LLCC. The LLCC was also relatively large, elongated and cloud free.

On September 29, by the time Nesat managed to re-develop ad 10 nautical miles (19 km; 12 mi) ragged eye, it made landfall over Wenchang in Hainan, China and started weakening again. Because of the poor shapre and disorganization at the LLCC, the typhoon could only maintain a maximum 1-min sustained windspeed of 65 knots (120 km/h; 75 mph). Even after the landfall, Nesat maintained vigorous convection all around the LLCC and did not weaken too much when compared to the reactions after the Philippine landfall. There was a sea-surface temperature of approximately 28 °C (82 °F) and a slight vertical wind shear of 10 knots (19 km/h; 12 mph) near the system's center at that time. The JTWC anticipated the storm to gradually drift over the Gulf of Tonkin and make landfall over Vietnam with a 1-min sustained wind speed of at-least 50 knots (93 km/h; 58 mph). Early on September 30, Nesat made its final landfall over northern Vietnam with a 1-mim sustained windspeed of 55 knots (102 km/h; 63 mph) and a well-defined, tightly wrapped LLCC, and soon it started weakening. Due to land interaction, the convection around the system started decaying rapidly. Due to the rapid weakening, the JTWC ceased advisories on the storm, soon afterwards. Later that evening, the JMA downgraded Nesat to a tropical low over land and issued their final warning on the system.

Similar to Typhoon Ketsana in 2009, Nesat caused further damage in Metro Manila along Roxas Boulevard. Around 63 flights were cancelled due to heavy rain and strong winds brought by the storm. The residents of Manila had no other choice but to wade into waist-deep floodwaters. The Philippine Stock Exchange and the US Embassy were forced to closed due to the heavy rains and strong winds brought by Nesat. Pre-school, elementary, high school, and college classes were suspended. Similar to the Tulane University during Hurricane Katrina in 2005, the Ospital ng Maynila Medical Center moved patients from the ground floor which was flooded in neck-deep waters. Hospital generators were flooded and the building had no power since the typhoon arrived. In Sofitel Philippine Plaza, the restaurant and the basement in the hotel was flooded as big waves broke into hotel windows. Around 37% of Manila Electric Company's service area was left without power after heavy rains and high winds had toppled down power lines. At least 95 people were killed and many were left missing. On September 28, the death toll from Nesat was put at 18 and the number of missing at 35 the day long rain and winds. The extremely high storm surges brought by the storm crashed into seawalls, flooded a hospital, a five-star hotel and the US Embassy near Manila. As more power lines were downed, nearly a million people in Luzon and some areas in the capital Manila remained without power for the rest of September 27 and 28. At least 5027 homes were destroyed and 40,699 families were left homeless and had to be evacuated.

Tropical Storm Haitang

Tropical storm (JMA)
Tropical storm (SSHWS)
Duration	September 24 – September 27
Peak intensity	65 km/h (40 mph) (10-min); 996 hPa (mbar)

On the evening of September 21, at almost the same time when Nesat was first seen, another low pressure area persisted far south of Hong Kong. The low slowly drifted north and strengthened slowly until on September 24, when the JMA upgraded the system to a tropical depression east of Vietnam. Later that day, the JTWC issued a Tropical Cyclone Formation Alert stating that the low could develop into a tropical cyclone. Only a few hours later, the JTWC initiated advisories on the system, designating it with 21W. Early the next day, the storm strengthened significantly that the JMA upgraded it to a tropical storm, naming it Haitang. Later that day, the storm developed a better organized but fully exposed low level circulation center (LLCC). The storm remained very weak with winds of just 35 knots (65 km/h; 40 mph) because of a moderate strength easterly vertical wind shear. By that night, the wind shear strengthened and pushed all the convection to the west-southwest keeping the storm relatively weak. Though a ridge building over china impinged poleward outflow, the euquatoward outflow remained significantly excellent. Haitang was also a slow-mover, moving westward at only 3 knots (5.6 km/h; 3.5 mph). However, by the night of September 26, Haitang rapidly accelerated west at over 13 knots (24 km/h; 15 mph) and made landfall over Vietnam. Though there was a burst of convection at that time, both land interaction and vertical wind shear weakened the system into a tropical depression and the JTWC ceased their advisories. The JMA tracked Haitang as a tropical depression until it finally dissipated inland Vietnam early on September 27.

Typhoon Nalgae (Quiel)

Main article: Typhoon Nalgae (2011)

Very strong typhoon (JMA)
Category 4 super typhoon (SSHWS)
Duration	September 26 – October 5
Peak intensity	175 km/h (110 mph) (10-min); 935 hPa (mbar)

On September 26, the Japan Meteorological Agency (JMA) started to monitor a weak tropical depression that had developed about 1,260 km (785 mi) to the northwest of Manila in the Philippines. During that day, while the depression moved towards the northwest its low level circulation centre rapidly consolidated in an area of favourable conditions for further development of the system. This prompted the Joint Typhoon Warning Center (JTWC) to issue a tropical cyclone formation alert on the system early the next day. However less than 3 hours later, the JTWC decided to issue advisories on the system designating it as Tropical Depression 22W, before the JMA reported that the depression had become a tropical storm and named it Nalgae.

The storm slowly drifted to the west and kept on intensifying gradually. Nalgae developed a microwave eye like feature and well defined convective banding in all the quadrants. The system had a tiny radius of winds, though it was still strengthening significantly and was very well defined. On the evening of September 28, the JMA reported that Nalgae continued to intensify, as they upgraded it to a severe tropical storm with winds of over 55 knots (102 km/h; 63 mph). On that night, the PAGASA initiated advisories on Nalgae, giving it the local name Quiel, as it entered the Philippine Area of Responsibility (PAR). Late on September 29, the JMA upgraded Nalgae to a typhoon. Nalgae rapidly intensified on September 30 and attained category 4 super typhoon status early on October 1, just before making landfall over Luzon. Due to land interaction and colder sea surface temperature in the South China Sea, the JMA downgraded Nalgae to a severe tropical storm on October 2 and then a tropical storm late on October 3. The JTWC downgraded Nalgae to a tropical depression on October 4, and the JMA also did it on the next day. Later on October 5, the remnant low of Nalgae dissipated.

Striking the Philippines just days after Typhoon Nesat, Nalgae caused further damage across Luzon. High winds and heavy rains from the storm caused widespread power outages and flooding that left many communities isolated. Nearly 2,900 homes were destroyed and approximately another 15,400 sustained damage. At least 18 people were killed by the storm and another 7 were reported as missing as of October 11. A total of 1,113,763 people were affected by the storm. Total losses in the country reached just over 115 million PHP ($2.62 million USD).

Tropical Storm Banyan (Ramon)

Tropical storm (JMA)
Tropical depression (SSHWS)
Duration	October 9 – October 16
Peak intensity	65 km/h (40 mph) (10-min); 1002 hPa (mbar)

On October 9, the JMA upgraded a low pressure area to a tropical depression northeast of Palau. Early on October 10, the JTWC upgraded the system to a tropical depression designating as 23W, and the PAGASA also upgraded it to a tropical depression and named it Ramon. On October 11, the JMA and the JTWC upgraded the system to a tropical storm and named it Banyan. Early on October 12, Banyan made landfall over Leyte, Philippines, and the JTWC downgraded it to a tropical depression. A half day later, the JMA also downgraded Banyan to a tropical depression. The system dissipated in the South China Sea, on October 16.

While tracking through the Philippines, Banyan produced heavy rains across much of the country, leading to widespread flooding. At least ten people were killed by the storm and another was reported missing. A total of 75,632 people were affected by the storm.

Tropical Depression

Tropical depression (JMA)
Duration	October 11 – October 13
Peak intensity	<55 km/h (35 mph) (10-min); 1006 hPa (mbar)

Late on September 28, a tropical disturbance formed east-southeast of Palau. Several days later, it became a low pressure area, crossed the Philippines, and arrived at the South China Sea. On October 11, the JMA upgraded the system to a tropical depression southeast of Hainan, China. Late on October 13, the system dissipated, just after making landfall over Vietnam.

Tropical Depression 24W

Tropical depression (JMA)
Tropical depression (SSHWS)
Duration	November 7 – November 10
Peak intensity	<55 km/h (35 mph) (10-min); 1004 hPa (mbar)

On November 5, a low pressure area has persisted west of the Philippines. On November 6, the low pressure area started to get organized as it is moving west towards Vietnam. On November 7, the low pressure became organized prompting the JTWC to issue a TCFA. On the same day, the JTWC upgraded the low pressure to a tropical depression and designated as 24W. On evening, the JMA also upgraded the system to a tropical depression. On November 8, the JTWC issued its final advisory on the system as it started weakening due to cold air from the north. On November 10, the JMA reported that the system weakened to a low pressure area.

Tropical Depression 25W

Tropical depression (SSHWS)
Duration	December 4 – December 5
Peak intensity	45 km/h (30 mph) (1-min); 1006 hPa (mbar)

On December 3, a low pressure area persisted west of Borneo. On December 4, the disturbance rapidly intensified, prompting the JTWC to issue a TCFA on it. Soon afterwards on that day, the JTWC upgraded the low pressure area to a tropical depression, and designated the storm as 25W. Early on December 5, the JTWC issued their final warning for 25W, due to the storm's interaction with the cold and dry air flow.

Tropical Depression 26W

Tropical depression (JMA)
Tropical depression (SSHWS)
Duration	December 10 – December 14
Peak intensity	55 km/h (35 mph) (10-min); 1004 hPa (mbar)

On December 8,a low pressure area formed over the Philippines and started to strengthen.On December 10,the JMA reported that the low pressure area has strengthened into a tropical depression west of the Palawan Island. Soon that day, the JTWC also issued a TCFA on the disturbance. On December 11, the JTWC cancelled the TCFA on the disturbance due to the interaction with the cold air coming from the north. In the Philippines, the National Disaster Risk Reduction and Management Council (NDRRMC) reported that 4 people were killed, due to the torrential rain. The tropical depression reached peak intensity during midday, on December 11, as it was located over the center, of the South China Sea. But later that day, the depression began to weaken rapidly, as the storm moved southeastward. However, the JTWC issued a TCFA on the disturbance again early on December 12 because of a decrease in vertical wind shear. After a few hours, the JTWC upgraded it to a tropical depression and designated as 26W. After a couple of days drifting southwestwards in the South China Sea, on December 13, the JTWC issued their final advisories on the system as it started to weaken. Late on December 14, the tropical depression dissipated near Borneo.

Severe Tropical Storm Washi (Sendong)

Main article: Tropical Storm Washi

Severe tropical storm (JMA)
Tropical storm (SSHWS)
Duration	December 13 – December 19
Peak intensity	95 km/h (60 mph) (10-min); 992 hPa (mbar)

On December 11, a disturbance formed and persisted near Chuuk. On December 13, the low pressure area rapidly intensified prompting the JTWC to issue a TCFA. On the same day, the JTWC upgraded the low pressure to a tropical depression and designated as 27W; in addition, the JMA also upgraded it to a tropical depression. The JTWC upgraded the system to a tropical storm on December 14 but downgraded it to a tropical depression early on December 15, and the PAGASA designated it Sendong as it entered the Philippine Area of Responsibility. After passing Palau on December 15, both the JTWC and the JMA upgraded the system to a tropical storm and named it Washi. On December 16, Washi made landfall over Surigao del Sur, a province of the Philippines located in Mindanao. Several hours later, Washi arrived at the Sulu Sea and regained its strength quickly, due to slight land interaction with Mindanao. Late on December 17, Washi crossed Palawan, and arrived at the South China Sea. On December 19, Washi weakened into a tropical depression and dissipated.

In the Philippines, Washi has caused at least 1,268 fatalities, and 1,079 people are officially listed as missing. Washi had affected 102,899 families or 674,472 people in 766 villages in 52 towns and eight cities in 13 provinces. The majority of the deaths were in the cities of Iligan and Cagayan de Oro. Five people were killed in a landslide, but all others died in flash flooding. More than 2,000 have been rescued, according to the Armed Forces of the Philippines. Officials were also investigating reports that an entire village was swept away. The flash flooding occurred overnight, following 10 hours of rain, compounded by overflowing rivers and tributaries. In some areas, up to 20 centimeters of rain fell in 24 hours. At least 20,000 people were staying in 10 evacuation centers in Cagayan de Oro. Officials said that despite government warning, some people did not evacuate. At least 9,433 houses were destroyed while 18,616 were damaged.

Tropical Depression

Tropical depression (JMA)
Duration	December 24 – December 24
Peak intensity	<55 km/h (35 mph) (10-min); 1004 hPa (mbar)

Late on December 24, the JMA upgraded a low pressure area to a tropical depression east-southeast of Mindanao. However, the system weakened to a low pressure area very soon, prompting the JMA to cancel all advisories on the storm.

Tropical Depression

Tropical depression (JMA)
Duration	December 31, 2011 – January 1, 2012
Peak intensity	<55 km/h (35 mph) (10-min); 1008 hPa (mbar)

On December 31, the JMA upgraded a low pressure area to a tropical depression east of Peninsular Malaysia. The system dissipated on January 1.

Retirement

See also: List of retired Pacific typhoon names (JMA) and List of retired Philippine typhoon names

The ESCAP/WMO Typhoon Committee announced that Washi will also be retired on its naming lists.

The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) announced that the names Bebeng, Juaning, Mina, Pedring were retired from PAGASA's list of local names after they each caused over 1 billion PHP in damages to the Philippines during 2011. The name Sendong was also retired from the list after it caused at least 1,257 deaths, when it made landfall on the Philippines during December 2011.

Season effects

This table lists all of the tropical cyclones that were monitored during the 2011 Pacific typhoon season. Information on their intensity, duration, name, areas affected, primarily comes from the warning centres while death and damage reports come from either press reports or the relevant national disaster management agency and include any impact that was associated with the system.

Storm Name	Dates active	Storm category at peak intensity	Peak 10-min sustained winds	Pressure	Areas affected	Damage (USD)	Deaths	References
01W	April 1 – 4	Tropical depression	55 km/h (35 mph)	1004 hPa (29.65 inHg)	None	None	None
02W (Amang)	April 3 – 6	Tropical depression	55 km/h (35 mph)	1000 hPa (29.53 inHg)	Northern Mariana Islands	None	None
Aere (Bebeng)	May 5 – 12	Tropical storm	75 km/h (45 mph)	992 hPa (29.29 inHg)	Philippines, Japan	$31.7 million	48
Songda (Chedeng)	May 19 – 29	Typhoon	195 km/h (120 mph)	920 hPa (27.17 inHg)	Micronesia, Philippines, Japan	$287 million	17
Tropical Depression	May 31 – June 2	Tropical depression	Unknown	1004 hPa (29.65 inHg)	None	None	None
Sarika (Dodong)	June 8 – 11	Tropical storm	75 km/h (45 mph)	996 hPa (29.41 inHg)	Philippines, China	$248 million	29
Tropical Depression	June 15 – 16	Tropical depression	Unknown	1004 hPa (29.65 inHg)	None	None	None
Haima (Egay)	June 16 – 25	Tropical storm	75 km/h (45 mph)	985 hPa (29.09 inHg)	Philippines, China, Vietnam, Laos	$16.7 million	18
Meari (Falcon)	June 20 – 27	Severe tropical storm	110 km/h (70 mph)	970 hPa (28.64 inHg)	Philippines, Japan, China, Korean islands	$1.24 million	11
Goring	July 9 – 10	Tropical depression	55 km/h (35 mph)	1000 hPa (29.53 inHg)	Japan, Taiwan	None	None
Ma-on (Ineng)	July 11 – 24	Typhoon	175 km/h (110 mph)	935 hPa (27.61 inHg)	Northern Mariana Islands, Japan	$27.8 million	5
Tokage (Hanna)	July 14 – 16	Tropical storm	65 km/h (40 mph)	1000 hPa (29.53 inHg)	None	None	None
Tropical Depression	July 16 – 17	Tropical depression	Unknown	998 hPa (29.47 inHg)	China	None	None
Tropical Depression	July 16	Tropical depression	Unknown	1002 hPa (29.59 inHg)	China	None	None
Nock-ten (Juaning)	July 24 – 31	Severe tropical storm	95 km/h (60 mph)	985 hPa (29.09 inHg)	Philippines, China, Vietnam, Laos, Thailand	$126 million	128
Muifa (Kabayan)	July 25 – August 9	Typhoon	175 km/h (110 mph)	930 hPa (27.46 inHg)	Micronesia, Philippines, Japan, China, South Korea, North Korea	$480 million	22
Lando	July 31 – August 2	Tropical depression	Unknown	1002 hPa (29.59 inHg)	None	None	None
Merbok	August 3 – 9	Severe tropical storm	95 km/h (60 mph)	980 hPa (28.94 inHg)	None	None	None
Tropical Depression	August 3 – 4	Tropical depression	55 km/h (35 mph)	1008 hPa (29.77 inHg)	None	None	None
13W	August 8 – 15	Tropical depression	55 km/h (35 mph)	1004 hPa (29.65 inHg)	None	None	None
Tropical Depression	August 8 – 10	Tropical depression	55 km/h (35 mph)	1008 hPa (29.77 inHg)	None	None	None
Tropical Depression	August 20 – 25	Tropical depression	55 km/h (35 mph)	1002 hPa (29.59 inHg)	None	None	None
Nanmadol (Mina)	August 21 – 31	Typhoon	185 km/h (115 mph)	925 hPa (27.32 inHg)	Philippines, Taiwan, China	$603 million	38
Talas	August 23 – September 5	Severe tropical storm	95 km/h (60 mph)	970 hPa (28.64 inHg)	Japan	$600 million	73
Noru	September 2 – 6	Tropical storm	75 km/h (45 mph)	990 hPa (29.23 inHg)	Sakhalin, Kuril Islands, Okhotsk
Kulap (Nonoy)	September 6 – 11	Tropical storm	65 km/h (40 mph)	1000 hPa (29.53 inHg)	Japan, South Korea	None	None
Roke (Onyok)	September 8 – 22	Typhoon	155 km/h (100 mph)	940 hPa (27.76 inHg)	Japan, Russia	$1.2 billion	16
Sonca	September 14 – 20	Typhoon	130 km/h (80 mph)	970 hPa (28.64 inHg)	None	None	None
Tropical Depression	September 14 – 15	Tropical depression	Unknown	1002 hPa (29.59 inHg)	None	None	None
Nesat (Pedring)	September 23 – 30	Typhoon	150 km/h (90 mph)	950 hPa (28.05 inHg)	Philippines, China, Hong Kong, Macau, Vietnam	$1.24 billion	95
Haitang	September 24 – 27	Tropical storm	65 km/h (40 mph)	996 hPa (29.41 inHg)	China, Vietnam	None	None
Nalgae (Quiel)	September 26 – October 5	Typhoon	175 km/h (110 mph)	935 hPa (27.61 inHg)	Philippines, China, Vietnam	$2.5 million	18
Banyan (Ramon)	October 9 – 16	Tropical storm	65 km/h (40 mph)	1002 hPa (29.59 inHg)	Palau, Philippines	$2.1 million	10
Tropical Depression	October 11 – 13	Tropical depression	Unknown	1006 hPa (29.71 inHg)	Vietnam	None	None
24W	November 7 – 10	Tropical depression	Unknown	1004 hPa (29.65 inHg)	None	None	None
25W	December 4 – 5	Tropical depression	Unknown	1006 hPa (29.65 inHg)	None	None	None
26W	December 10 – 14	Tropical depression	55 km/h (35 mph)	1004 hPa (29.65 inHg)	Philippines	None	4
Washi (Sendong)	December 13 – 19	Severe tropical storm	95 km/h (60 mph)	992 hPa (29.29 inHg)	Federated States of Micronesia, Palau, Philippines	$48.4 million	1268
Tropical Depression	December 24	Tropical depression	Unknown	1004 hPa (29.65 inHg)	None	None	None
Tropical Depression	December 31 – January 1	Tropical depression	Unknown	1008 hPa (29.77 inHg)	Malaysia	None	None
Season Aggregates
Total Depressions: 40	April 1 – January 1		195 km/h (120 mph)	920 hPa (27.17 inHg)		$4.9 billion	1,800

See also

• List of Pacific typhoon seasons
• 2011 Pacific hurricane season
• 2011 Atlantic hurricane season
• 2011 North Indian Ocean cyclone season
• South-West Indian Ocean cyclone seasons: 2010-11, 2011-12
• Australian region cyclone seasons: 2010-11, 2011-12
• South Pacific cyclone seasons: 2010-11, 2011-12

External links

• China Meteorological Agency
• Digital Typhoon
• Hong Kong Observatory
• Japan Meteorological Agency
  • Multilingual Tropical Cyclone Information
• Joint Typhoon Warning Center
• Korea Meteorological Administration
• Malaysian Meteorological Department
• National Weather Service Guam
• Philippine Atmospheric, Geophysical and Astronomical Services Administration
• Taiwan Central Weather Bureau
• TCWC Jakarta
• Thai Meteorological Department
• Typhoon2000
• Vietnam's National Hydro-Meteorological Service