File:Typhoon Koinu (MODIS).jpg

English: After skirting north of the Philippines, Typhoon Koinu approached the southeastern coast of Taiwan on October 4, 2023. The storm was forecast to make landfall on the island the following morning.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired this true-color image of Koinu at approximately 1 p.m. local time on October 4. The storm’s eye was about 200 kilometers (125 miles) off the coast of Taiwan and moving westward over the sea at 13 kilometers (8 miles) per hour, according to the Joint Typhoon Warning Center. Sustained wind speeds reached an estimated 210 kilometers (130 miles) per hour, nudging it into the equivalent of a Category 4 hurricane.

Taiwanese authorities issued weather alerts in anticipation of strong winds and heavy rain lashing the southeastern part of the island. Flights were canceled, schools and businesses were closed, and fishermen secured their boats, according to news reports. While the heaviest rain is expected to fall on mountainous and sparsely populated regions, the storm will also impact the major port city of Kaohsiung.

As Koinu passes over land, mountainous terrain should cause it to weaken but the exact path of the storm will dictate how much the topography influences its intensity. From there, forecasts show it continuing to lose strength as it leaves the island, then approaches and skirts the coast of China.

While the storm was still offshore, subsiding air on its outer edges contributed to extreme heat in South China. On October 4, Hong Kong registered its hottest day on record for the month of October. Temperatures reached 34.6 degrees Celsius (94.3 Fahrenheit), the Hong Kong Observatory reported.

Several typhoons have affected this region in 2023, including Mawar in May, Doksuri in July, and Saola and Haikui in September. The Western Pacific typhoon season can span the entire year, though most storms develop between May and October.