![\"Topography](\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2018\/11\/181107_suomiNPP_viirs_infraredWindow_250winds_AK_banner_cloud_anim.gif\")
<\/a>Topography + Suomi NPP VIIRS Infrared Window (11.45 \u00b5m<\/em>) images, with\/without overlays of NAM12 250 hPa winds [click to play animation | MP4<\/strong><\/a>]<\/p><\/div>Suomi NPP VIIRS Infrared Window (11.45 \u00b5m) images (above)<\/strong><\/em> showed a well-defined banner cloud extending from the Brooks Range in northern Alaska to the Beaufort Sea on 07 November 2018. Overlays of NAM12 model 250 hPa winds revealed the presence of a branch of the polar jet stream flowing northeastward over the region. Strong southwesterly winds interacting with the topography<\/strong><\/a> of the Brooks Range created a standing wave which led to the formation of the banner cloud.<\/p>\n In a comparison of Suomi NPP VIIRS Shortwave Infrared (3.74 \u00b5m) and Infrared Window (11.45 \u00b5m) images (below),<\/strong><\/em> note the significantly warmer 3.74 \u00b5m cloud-top brightness temperatures — as much as 40 to 50\u00baC warmer at 2009 UTC<\/strong><\/a> when the sun angle was highest over Alaska — caused by enhanced solar reflectance off the very small ice crystals at the top of the banner cloud.<\/p>\n Suomi NPP VIIRS Shortwave Infrared (3.74 \u00b5m)<\/em> and Infrared Window (11.45 \u00b5m)<\/em> images [click to play animation | MP4<\/strong><\/a>]<\/p><\/div>GOES-15 (GOES-West)<\/em> Water Vapor (6.5 \u00b5m) and Infrared Window (10.7 \u00b5m) images (below)<\/strong><\/em> showed that a large banner cloud had persisted downwind of the Brooks Range fpr much of the day.<\/p>\n<\/a>