JMA Himawari-9 Clean Infrared Window (10.4 µm) images, from 0602 UTC to 2347 UTC [click to play animated GIF | MP4]

Target Sector (2.5-minute interval) JMA Himawari-9 AHI Clean Infrared Window (10.4 µm) images (above) showed Typhoon Koina after it intensified to a Category 4 storm at 0600 UTC on 04 October 2023 (SATCON). The coldest cloud-top infrared brightness temperatures (-80 to -89C, shades of violet to purple) were generally confined to the southern semicircle of the storm. A faster animation (GIF | MP4) revealed a bit of trochoidal motion (wobble) to Konu’s eye.

Even though Koinu was traversing an area of warmer water (Sea Surface Temperature | Ocean Heat Content ), it was moving through an environment of increasing deep-layer wind shear (source). The general satellite presentation began to deteriorate as it approached the far southern tip of Taiwan, making landfall around 2332 UTC.

A toggle between Suomi-NPP VIIRS Day/Night Band (0.7 µm) images valid at 0450 UTC and 1719 UTC (below) also displayed the deterioration of Koinu’s eye during that 12-hour period.

Suomi-NPP VIIRS Day/Night Band (0.7 µm) images valid at 0450 UTC and 1719 UTC [click to enlarge]

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