![](\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/images\/2024\/12\/241220_himawari9_visible_shortwaveInfrared_infraredWindow_Australia_pyroCb_anim.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 0330-0640 UTC on 20th December, with hourly plots of surface reports [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 20th December 2024. The pyroCb cloud exhibited cloud-top 10.4 \u00b5m infrared brightness temperatures (IRBTs) of -40\u00baC and colder (denoted by the shades of blue) \u2014 attaining a minimum IRBT of -44\u00ba C at 0530 UTC<\/strong><\/a> (the air temperature at an altitude around 10 km, according to rawinsonde data from Melbourne: plot<\/strong><\/a> | text<\/strong><\/a>). The pyroCb cloud eventually drifted southeast over Melbourne Airport (YMML).<\/p>\n Himawari-9 True Color RGB images created using Geo2Grid<\/strong><\/a> (below)<\/strong><\/em> displayed the broad smoke plume that was being transported east-southeastward from the Grampians bushfire — along with the high-altitude pyroCb cloud that cast a shadow upon the smoke layer below.<\/p>\n JMA Himawari-9 True Color RGB images, from 0350-0640 UTC on 20th December [click to play animated GIF | MP4<\/strong><\/a>]<\/p><\/div>A NOAA-20 (mislabeled as NPP) VIIRS Day\/Night Band (0.7 \u00b5m) image valid at 0450 UTC (below)<\/strong><\/em> provided another view of the pyroCb cloud shortly after its formation.<\/p>\n NOAA-20 VIIRS Day\/Night Band (0.7 \u00b5m) image valid at 0450 UTC on 20th December; the 0500 UTC surface report for Melbourne Airport YMML is plotted in cyan [click to enlarge]<\/p><\/div>As a surface trough of low pressure was moving east-northeastward across the state of Victoria (surface analyses<\/strong><\/a>), strong S-SW winds behind the trough axis (surface observations at Melbourne<\/strong><\/a> and Avalon<\/strong><\/a>) helped to intensify the Grampians fire complex — 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 rapid northward run of the Grampians bushfire following the ~0400 UTC trough passage, (2) the pyroCb formation shortly after the time of the trough passage, and (3) the northeastward surge of cooler air (darker shades of purple over cloud-free land surfaces) in the wake of the trough passage. 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><\/a>