On September 26, a tropical depression developed approximately 1,445 km east-northeast of Guam. Despite a marginally favorable environment, the Japan Meteorological Agency upgraded the system to a tropical storm and assigned it the name Chaba late the next day. Early on September 28, the Joint Typhoon Warning Center gave the identifier of 21W. Flaring convection and improved overall convective structure prompted the JTWC to upgrade it to a tropical storm. By September 30, Chaba had intensified into a severe tropical storm after deep convection had evolved into a banding feature and very favorable conditions such as very low wind shear and sea surface temperatures of about 30 degrees Celsius. On October 1, Chaba entered the Philippine area of responsibility, with PAGASA assigning the local name Igme, as it started to move in a northwestward direction. Several hours later, both agencies upgraded Chaba to a typhoon after its organization and structure had vastly improved. During the next day, Chaba became more symmetric as feeder bands wrapped into its deep central convection, signalling the onset of explosive intensification. Continuing its strengthening trend, Chaba reached Category 5 super typhoon intensity with a sharp wide eye surrounded by a very intense convective core due to very warm SSTs. On October 3, Chaba reached its peak intensity with 10-minute sustained winds of 215 km/h, 1-minute sustained winds of 280 km/h, and a minimum central pressure of 905 mbar. Thereafter, the JTWC stated that Chaba began weakening, as its core became asymmetric, and Chaba weakened to a strong Category 4 typhoon by October 4. Later, significant weakening led the JTWC to downgrade Chaba further to a Category 2 typhoon, due to interaction with strong north-northeasterly winds. At 10:00 a.m. KST, Chaba struck Geojedo and then made landfall in Busan an hour later with winds of 120 km/h. At that time, Chaba started to undergo extratropical transition and the JTWC issued its final advisory a few hours later, while downgrading the system to a tropical storm. At the same time, the JMA downgraded Chaba to a severe tropical storm. Six hours later, the JMA issued its final advisory, as Chaba became extratropical.
Preparations and impact
and China Airlines canceled flights to Okinawa that had been scheduled for 3 October, which was the day the typhoon was forecast to impact Okinawa. EVA Air had previously been criticized for operating flights to destinations affected by typhoons a week earlier, when Typhoon Megi was affecting the region. The storm left widespread damage across the southern regions of South Korea, killing at least 7 and leaving 3 missing. Transportation was disrupted, with hundreds of flights canceled, while more than 220,000 households lost electricity. Chaba was the strongest typhoon to strike the country since Sanba in 2012, and was the strongest October typhoon to hit Korea, establishing a new record for rainfall rate on Jeju Island. Flooding was also reported in the southern South Korea cities of Ulsan, Gyeongju, and Busan. Damages were reported at billion.
