Typhoon Lionrock (12W) in the West Pacific Ocean briefly intensified to Category 4 during the northeastward motion segment of its rather unusual track (above) — the intensity estimate from the Advanced Dvorak Technique peaked at 112.4 knots from 2140 UTC on 26 August to 0630 UTC on 27 August (plot | text).

During this period of intensification, 2.5 minute interval rapid-scan Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images (below; also available as a large 85 Mbyte animated GIF) revealed complex patterns of cloud-top radial and transverse banding. Surface mesoscale vortices were also seen at times within the open eye feature.

A few hours later, the Category 3 intensity typhoon continued to exhibit a well-defined eye structure in both DMSP-15 SSMI Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images around 18 UTC (below).

During the nighttime hours preceding the intensification to Category 4, a comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (below; courtesy of William Straka, SSEC) showed the eye of Lionrock at 1631 UTC on 26 August.

===== 28 August Update =====

Typhoon Lionrock again intensified to a Category 4 storm on 28 August; a comparison of 2.5 minute interval rapid-scan Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images is shown above (also available as a large 68 Mbyte animated GIF).