This timeline documents all of the events of the 2011 Pacific typhoon season, the period that tropical cyclones formed in the Western Pacific Ocean in 2011. Most of the tropical cyclones formed between May and November 2011. The scope of this article is limited to the Pacific Ocean, north of the equator between 100°E and the International Date Line. Tropical storms that form in the entire Western Pacific basin are assigned a name by the Japan Meteorological Agency (JMA). Tropical depressions that form in this basin are given a number with a "W" suffix by the United States' Joint Typhoon Warning Center (JTWC). In addition, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) assigns names to tropical cyclones (including tropical depressions) that enter or form in the Philippine area of responsibility. These names, however, are not in common use outside of the Philippines.
During the season, a total of 40 systems were designated as Tropical Depressions by either the Japan Meteorological Agency (JMA), the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), the Joint Typhoon Warning Center (JTWC), or other national meteorological and hydrological services such as the China Meteorological Administration and the Hong Kong Observatory. Because the JMA runs the Regional Specialized Meteorological Centre for the Western Pacific, it assigns names to Tropical Depressions should they intensify into a tropical storm. PAGASA also assigns local names to tropical depressions which form within their area of responsibility; however, these names are not in common use outside of PAGASA's area of responsibility.
For the PAGASA, 19 systems formed or entered in area of responsibility during 2011, which 10 of them directly made landfall over the Philippines. No tropical cyclones formed during January to March. The season started on April 1 with the formation of Tropical Depression 01W.
Timeline
January
January 1 The 2011 Pacific typhoon season officially starts; no tropical cyclones developed during January.
February
No tropical cyclones formed during February.
March
March 30 1800 UTC - A disturbance formed southwest of Yap.
March 31 0600 UTC - The disturbance continued and intensified to a depression the next day.
April
April 1 0600 UTC — The JMA reports that a tropical depression has developed, about to the southeast of Ho Chi Minh City in Southern Vietnam.
April 2 0300 UTC — The JTWC initiates advisories on the tropical depression and designates it as Tropical Depression 01W. 1200 UTC — The JTWC reports that Tropical Depression 01W has reached its peak intensity, with 1 — minute sustained windspeeds of .
April 3 0900 UTC — The JTWC issues its final advisory on Tropical Depression 01W, as the system weakens into a tropical disturbance. 02W entered the Philippine area of responsibility receiving the name Amang. 1800 UTC — The JTWC reports that
April 4 0600 UTC — The JMA issues its final advisory on Tropical Depression 01W.
April 6 1200 UTC - Tropical Depression Amang dissipates as it rapidly moves northeast.
May
May 5 0600 UTC - The JMA started monitoring a disturbance from a monsoon trough.
May 6 0300 UTC - The PAGASA received the name Bebeng as it slowly intensifies, bringing intense rainfall over the Philippines. 0900 UTC - The JTWC finally recognizes the system as Tropical Depression 03W.
May 7 0000 UTC - The JMA upgraded it to Tropical Storm Aere as it now steadily intensifies in the Philippine Sea.
May 8 0900 UTC - Aere reaches peak intensity as a strong tropical storm but failed to be a Severe Tropical Storm, or even a minimal typhoon. 1300 UTC - Tropical Storm Aere slowly weakens as it destructs Philippines on May 8.
May 12 0300 UTC - Tropical Depression Aere dissipates over Japan.
May 13 2100 UTC - The remnants of Aere had completely dissipated as it was absorbed by a developing extratropical system.
May 19 0000 UTC - A newly formed tropical disturbance was classified by the JTWC. 1500 UTC - Due to favorable conditions of this new system, the JMA classified it as a weak tropical depression.
May 20 0600 UTC - The JTWC now classifies it as a tropical depression, giving the designation 04W.
May 21 0000 UTC - 04W strengthens into a Tropical Storm, naming it Songda as it grew larger in size. 0900 UTC - The PAGASA sees Tropical Storm Songda entering their area giving the name Chedeng.
May 23 2100 UTC - The JMA classifies Songda to a severe tropical storm. 2200 UTC - Songda starts its rapid deepening phase.
May 24 1200 UTC - Severe Tropical Storm Songda rapidly intensifies into a Typhoon as it hits eastern Philippines.
May 25
0900 UTC - Typhoon Songda maintain its strength as a Category 5 super typhoon. 1200 UTC - Songa ends its rapid deepening phase as it starts to rapidly weaken.
May 29 0600 UTC - Typhoon Songda dissipates in the same area where Aere dissipates.
May 31 0600 UTC - Just like Aere, the remnants of Songda finally dissipate. 1500 UTC - The JMA reports that a weak depression embedded from the monsoon, developed east of the Philippines bringing heavy rainfall. 1800 UTC - The PAGASA classified it as an Active Low-Pressure Area (ALPA).
June
June 2 0600 UTC - The depression dissipated as it failed to become a weak tropical storm.
June 8 0300 UTC - A low pressure area formed west of Cebu City. 1200 UTC - It was upgraded to Tropical Depression Dodong later that day.
June 10 0600 UTC - The JMA upgrades it to Tropical Storm Sarika as it moves north with only few convection. 0900 UTC - The JTWC classified it as a tropical depression.
June 11 1500 UTC - Sarika weakens at moves north towards Taiwan. 1800 UTC - Both agencies made their final advisories on Sarika as it made landfall over Southern China. 2100 UTC - Tropical Storm Sarika dissipates over southern China and Hong Kong.
June 14 0300 UTC - A tropical disturbance formed southwest of Manila, Philippines and rapidly intensified into a tropical depression by the JMA.
June 15 0600 UTC - The depression became disorganized as it finally dissipated, without the PAGASA naming it. 1500 UTC - The JTWC monitors a zone of disturbed weather over southeast of Manila, Philippines.
June 16 0300 UTC - The JTWC classifies it as a weak disturbance. 1200 UTC - It then rapidly intensified and was classified as Tropical Depression 06W as it steadily moved towards favorable conditions.
June 17 0000 UTC - The PAGASA upgraded the LPA to Tropical Depression Egay as it is now located east of the Philippines. 1800 UTC - Only the JTWC upgraded 06W to a tropical storm, while JMA classifies it as a tropical depression.
June 20 1500 UTC - 06W (Egay) weakens. 1600 UTC - A tropical depression formed from an Intertropical Convergence Zone (ITCZ).
June 21 0000 UTC - 06W degenerates to a tropical depression a it finally moves towards warm waters. 0600 UTC - Tropical Storm Haima exits the PAR and PAGASA made its final advisories on Egay as it brings heavy rains over eastern Philippines. 1200 UTC - Tropical Depression Egay becomes Tropical Storm Haima by the JMA as it enters the South China Sea. 1500 UTC - PAGASA expects 2 low-pressure areas entering the PAR as one of them has intensified into a tropical depression. 1800 UTC - The tropical depression was seen by the PAGASA and was named Falcon. 2100 UTC - The JTWC made warnings of Falcon to Tropical Depression 07W as it moves northwest towards a large area of convection and a cluster of thunderstorms.
June 22 0000 UTC - Tropical Depression Falcon absorbed more rainbands from the active ITCZ as it became a Tropical Storm naming it Meari.
June 23 Tropical Storm Haima makes landfall in Zhanjiang, Guandong, China. Tropical Storm Meari intensifies as it enters dry air and deep convection and became a Severe Tropical Storm the next day and enters Okinawa, Japan late on June 23.
June 25 Tropical Storm Haima slowly dissipates over land as it moves southwest.
June 27 Severe Tropical Storm Meari dissipates and made landfall in Korea killing 9.
July
July 7
July 9 1800 UTC - A tropical disturbance formed east of Aurora. 2300 UTC - It was upgraded to Tropical Depression Goring by the PAGASA as it brought rainfall towards eastern Philippines.
July 11 1800 UTC - A tropical disturbance rapidly intensified to a tropical depression on July 11 as it moves towards an area of warm waters.
July 12 0300 UTC - The depression was designated 08W. 0900 UTC - 08W rapidly becomes Tropical Storm Ma-on.
July 13 0600 UTC - A new tropical depression was located in the Philippine Sea and PAGASA naming it as Hanna.
July 14 0300 UTC - JTWC upgrades Hanna to Tropical Depression 14W and JMA was upgraded to Tropical Storm Tokage. 0900 UTC - Typhoon Ma-on rapidly becomes a Category 3 typhoon as it is expected to hit Japan.
July 15 1200 UTC - Tokage was absorbed by Typhoon Ma-on as it became a Category 4 typhoon from the fujiwhara effect. 2100 UTC - The JTWC made its final advisories on Tokage.
July 17 Typhoon Ma-on enters the Philippine area of responsibility in a short matter of time as it is being named Ineng.
July 20 Typhoon Ma-on steadily weakens as it made landfall in Wakayama.
July 23 Tropical Storm Ma-on weakens to a tropical depression and dissipates the next day. Tropical Depression Juaning forms east of the Philippines as deep convection wrapped up Juaning and was designated 10W.
July 25 Juaning was upgraded to Tropical Storm Nock-ten as it struck land in the Philippines.
July 27 Nock-ten creates an unbalanced eye in a short time as it became a Severe Tropical Storm by the JMA but the JTWC upgraded it to a typhoon. Tropical Depression 11W forms west of Guam.
July 28 11W intensifies to Tropical Storm Muifa as it intensified and enters the PAR given the name Kabayan. Tropical Storm Nock-ten enters the South China Sea on July 28 and intensifies again to a strong Tropical Storm.
July 30 Severe Tropical Storm Muifa rapidly becomes a minimal typhoon as it heads straight north affecting the Philippines by the southwest monsoon. Nock-ten impacts the south China cost as it dissipates the next day. A disturbance formed northwest of Manila from the southwest monsoon, which is being enhanced by Typhoon Muifa.
July 31 Deep convection occurred as the disturbance became a tropical depression naming it Lando By the PAGASA. Typhoon Muifa started creating an eyewall as it began explosive intensification.
August
August 1 1800 UTC - Tropical Depression Lando slowly dissipates as it enhances the southwest monsoon. 2100 UTC - Typhoon Muifa steadily weakens as it still heads straight north towards Korea.
August 2 0300 UTC - Tropical Depression Lando dissipates and is absorbed by the southwest monsoon, bringing intense rainfall over northern Philippines. 0600 UTC - Tropical Depression 12W formed near the Wake Islands. 1200 UTC - Category 3 typhoon Muifa rapidly turns west as it weakens to a minimal typhoon.
August 4 1800 UTC - 12W rapidly intensified to Tropical Storm Merbok. 2100 UTC -Muifa entered land and destruct Shanghai on August 4 as it rapidly weakens to a Subtropical storm.
August 7 0000 UTC - The JMA classifies Merbok as a severe tropical storm. 1500 UTC - Merbok intensifies into a minimal typhoon by the JTWC.
August 8 0300 UTC - Mebok rapidly weakens over cool waters as it accelerates north on August 8, as an extratropical transition. 0600 UTC - Subtropical depression Mufia becomes extratropical as it dissipates on August 9. 0900 UTC - A tropical depression forms west of Guam.
August 10 0900 UT - JTWC designates it as 13W, as it absorbs few moisture and moves in a north northwest motion. August 15 0300 UTC - Tropical Depression 13W failed to be a tropical storm as it dissipated to a remnant low in a subtropical ridge.
August 20 1500 UTC - A tropical low developed north of Palau as it developed a low-level circulation center.
August 22 0000 UTC - It developed into a depression, naming it Mina by the PAGASA.