Banner cloud in Alaska
Suomi NPP VIIRS Infrared Window (11.45 µm) images (above) 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 of the Brooks Range created a standing wave which led to the formation of the banner cloud.In a comparison of Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images (below), note the significantly warmer 3.74 µm cloud-top brightness temperatures — as much as 40 to 50ºC warmer at 2009 UTC 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.
GOES-15 (GOES-West) Water Vapor (6.5 µm) and Infrared Window (10.7 µm) images (below) showed that a large banner cloud had persisted downwind of the Brooks Range fpr much of the day.