JMA Himawari-9 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.4 µm, bottom) images, from 2132 UTC on 01 October to 0902 UTC on 02 October [click to play animated GIF | MP4]

Target Sector (2.5-minute interval) JMA Himawari-9 AHI Visible and Infrared images (above) showed Typhoon Koina as it intensfied to a Category 3 storm by 0000 UTC on 02 October 2023 (SATCON). Cloud-top infrared brightness temperatures were as cold as -90C.

Just prior to the start of the Himawari-9 animation, an image of RCM-3 Synthetic Aperture Radar (SAR) winds at 2122 UTC on 01 October (source) is shown below — which depicted a narrow but fully closed eyewall.

RCM-3 Synthetic Aperture Radar image at 2122 UTC on 01 October [click to enlarge]

Later in the day, Himawari-9 Infrared Window (11.2 µm) images with an overlay of deep-layer wind shear at 2100 UTC — from the CIMSS Tropical Cyclones site (below) indicated that Koinu was moving through an environment where the shear (around 15 knots) was favorable. In addition, Koinu was traversing warm water (Ocean Heat Content | Sea Surface Temperature).

Himawari-9 Infrared Window (11.2 µm) images, with an overlay of deep-layer wind shear at 2100 UTC [click to enlarge]

—————
Free Secure Email – Transcom Sigma
Transcom Hosting
Transcom Premium Domains