Severe Tropical Storm Kompasu, known in the Philippines as Severe Tropical Storm Maring was a very large and deadly tropical cyclone that affected the Philippines, Taiwan, and southeast China. Part of the 2021 Pacific typhoon season, Kompasu originated from an area of low pressure east of the Philippines on 6 October 2021. The Japan Meteorological Agency (JMA) classified it as a tropical depression that day. A day later, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) classified it as a tropical depression, naming it Maring. The cyclone was initially heavily disorganised, competing with another vortex, Tropical Depression Nando. Eventually, Maring became dominant, and the JMA reclassified it as a tropical storm, naming it Kompasu. Kompasu made landfall in Cagayan, Philippines, on 11 October 2021, and two days later, the storm made landfall in Hainan, China. The cyclone dissipated on 14 October 2021 while located over Vietnam.
According to the National Disaster Risk Reduction and Management Council (NDRRMC), 43 people died from the storm in the Philippines, with 17 missing. Damage is estimated at ₱6.4 billion (US$127 million). In Hong Kong, one person died and 21 people were injured. The storm impacted many areas previously affected by Tropical Storm Lionrock a few days prior. According to Aon Benfield, economic losses outside the Philippines totaled US$118 million, with a grand total of US$245 million in economic losses.
Meteorological history
At 18:00 UTC (Coordinated Universal Time) on 6 October 2021, the JMA noted that an area of low pressure embedded within a large monsoonal circulation had formed to the north of Palau. The system developed into a tropical depression at 00:00 UTC of the next day. At 09:00 UTC (17:00 PHT) on 7 October, PAGASA issued its first bulletin for the depression, and assigned it the name Maring. The JMA also noted the persistence of another, nearby tropical depression to its Northeast, later named Nando. As it is embedded in the same monsoonal depression and due to its proximity, Nando began to merge with Maring, and therefore formed a very broad and large circulation at a diameter of 1900 km, beating Lekima of 2007 by 200 km. This prompted the JMA to upgrade the overall system to a tropical storm, and was named Kompasu. However at that time, the JTWC still considered the system as two separate disturbances and issued separate TCFAs later in the day for both depressions, albeit noting the possibility of merging. The JTWC later considered the entire system as merged with their first warning for Kompasu. At midnight of 11 October, the JMA upgraded it to a severe tropical storm, as it attained good cloud characteristics. At 12:10 UTC (20:10 PHT) on 11 October, Kompasu made landfall on Fuga Island, Cagayan, as a severe tropical storm. At 05:00 PHT of 13 October (21:00 UTC of 12 October), the PAGASA issued its final bulletin as its exited the PAR and continued towards Hainan. Between 03:00 and 09:00 UTC of 13 October, Kompasu had made landfall over the east coast of Hainan. By 18:00 UTC, the JMA downgraded it to a tropical storm, as it crossed the entire island and entered the Gulf of Tonkin, as its convection had rapidly weakened because of the rough terrain of the island. At 09:00 UTC of the next day, the JTWC issued its final warning followed by downgrading to a tropical depression, as its convection had diminished and the low-level circulation center had been weakened significantly because of the increasing vertical wind shear and dry air, despite not making landfall over northern Vietnam. The JMA issued its final warning after downgrading it to a tropical depression at 18:00 UTC.