![](\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/images\/2025\/02\/HIM09_VIS_SWIR_IR_AUS_PYROCB_04FEB2024_loop_HIMAWARI-9_2025035_030000_2025035_051000.gif\")
<\/a>JMA Himawari-9 \u201cRed\u201d Visible (0.64 \u00b5m, top), Shortwave Infrared (3.9 \u00b5m, center) and \u201cClean\u201d Infrared Window (10.4 \u00b5m, bottom) images from 0300-0510 UTC on 4th February, with plots of surface reports at Melbourne YMML [click to play animated GIF | MP4<\/strong><\/a>]<\/p><\/div>10-minute JMA<\/strong><\/a> Himawari-9 AHI<\/strong><\/a> \u201cRed\u201d Visible (0.64 \u00b5m), Shortwave Infrared (3.9 \u00b5m) and \u201cClean\u201d Infrared Window (10.4 \u00b5m) images (above)<\/strong><\/em> showed the formation of a pyrocumulonimbus<\/strong><\/a> (pyroCb) cloud that was spawned by a bushfire in Grampians National Park<\/strong><\/a> in far southeast Australia on 4th February 2025. The pyroCb exhibited cloud-top 10.4 \u00b5m infrared brightness temperatures (IRBTs) in the -40s C (denoted by shades of blue to cyan), attaining a minimum IRBT of -49.9\u00ba C at 0430 UTC<\/strong><\/a>. This temperature roughly corresponded to an altitude around 11 km — not far below the tropopause — according to rawinsonde data from Melbourne: (plot<\/strong><\/a> | text<\/strong><\/a>). The pyroCb cloud drifted southeast, eventually passing just south of Melbourne Airport (YMML).<\/p>\n Himawari-9 True Color RGB images created using Geo2Grid<\/strong><\/a> (below)<\/em><\/strong> displayed the pyroCb cloud that was being transported southeastward — and dense smoke (shades of tan) was evident in the vicinity (and immediately downwind) of the Grampians bushfire.<\/p>\n JMA Himawari-9 True Color RGB images, from 0250-0600 UTC on 4th February [click to play animated GIF | MP4<\/strong><\/a>]<\/p><\/div>As a surface trough of low pressure was moving east-northeastward across the state of Victoria during that time period (surface analyses<\/strong><\/a>), strong southerly winds behind the trough axis (surface observations at Melbourne<\/strong><\/a>) helped to intensify the Grampians fire complex \u2014 and the pyroCb cloud developed just after the trough passed through the area. Himawari-9 Fire Temperature RGB<\/strong><\/a> images (below)<\/strong><\/em> revealed (1) the northward expansion of the Grampians bushfire following the ~0300 UTC trough passage (along with flare-up of new fires to the NW), and (2) the pyroCb formation just after the time of the trough passage (0340 UTC image<\/strong><\/a>). Note that in the Himawari-9 True Color RGB images shown above, the trough passage also initiated a northward transport of boundary layer smoke from the bushfire source region.<\/p>\n<\/a>