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Cyclone Freddy reaches Category 4 intensity

By Scott Bachmeier •

JMA Himawari-9 Infrared Window (10.4 µm) images [click to play animated GIF | MP4]

JMA Himawari-9 Infrared Window (10.4 µm) images (above) showed Cyclone Freddy in the South Indian Ocean as it was rapidly intensifying from a Category 1 to a Category 3 storm by 12 UTC on 11 February 2023 (JTWC discussion), eventually presenting a ragged eye for several hours — then briefly reaching Category 4 intensity at 00 UTC on 12 February (SATCON | JTWC discussion). Overshooting tops within the eyewall of Freddy occasionally exhibited cloud-top infrared brightness temperatures of -90ºC and colder (yellow pixels embedded within darker purple regions).

A NOAA-20 VIIRS Day/Night Band (0.7 µm) image valid at 1825 UTC on 11 February (below) showed the eye of Freddy.

NOAA-20 VIIRS Day/Night Band (0.7 µm) image, valid at 1825 UTC on 11 February [click to enlarge]

Himawari-9 Infrared Window (11.2 µm) images from the CIMSS Tropical Cyclones site (below) include contours and streamlines of deep-layer (850-200 hPa) wind shear. The intensification of Freddy occurred in spite of this unfavorable environment of moderate to strong eaterly shear — however, the storm was moving over relatively warm water (with Sea Surface Temperature values around 29ºC).

JMA Himawari-9 Infrared Window (11.2 µm) images, with contours and streamlines of 850-200 hPa wind shear

RCM/Radarsat-2 SAR winds at 1136 UTC on 11 February (source) are shown below — a maximum wind speed of 106 knots was indicated within the northeast quadrant.

Radarsat-2 winds at 1136 UTC [click to enlarge]

Categories: Himawari-9, NOAA-20, RealEarth, SAR, Satellite winds, Tropical cyclones, VIIRS