Standing wave clouds over Virginia and North Carolina

March 7th, 2019 |

GOES-16

GOES-16 “Red” Visible (0.64 µm), “Clean” Infrared Window (10.3 µm), Cloud Top Height, Cloud Particle Size Distribution, and Cloud Phase [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm), “Clean” Infrared Window (10.3 µm), Cloud Top Height, Cloud Particle Size Distribution, and Cloud Phase (above) helped to characterize standing wave clouds that developed to the lee of the Appalachian Mountains on 07 March 2019. The primary standing wave rotor clouds were composed of smaller supercooled water droplets,  with “banner clouds” composed of larger/colder ice crystals forming downwind of the rotor clouds. For example, at 1637 UTC cloud particle sizes associated with the rotor clouds were as small as 3-10 µm (darker shades of purple).

GOES-16 Day Cloud Phase Distinction Red-Green-Blue (RGB) images from the AOS site (below) also identified the rotor clouds as supercooled water droplet features (brighter shades of white), with the banner clouds being identified as high-level ice (shades of pink) or glaciating (shades of green) features. An unrelated phenomena was the brief brightening of the bare ground across much of the Southeast US midway through the animation — a result of transient solar reflectance that is seen around the Spring and Autumn equinox.

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

In a comparison of 1-km resolution Terra MODIS Visible (0.65 µm), Near-Infrared “Cirrus” (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images at 1631 UTC (below), note that the standing wave rotor clouds appeared much warmer (darker gray) in the Shortwave Infrared images — this is due to the fact that small supercooled water droplets are very efficient reflectors of incoming solar radiation.

Terra MODIS Visible (0.65 µm), Near-Infrared

Terra MODIS Visible (0.65 µm), Near-Infrared “Cirrus” (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images [click to enlarge]

There were a few pilot reports of light to moderate turbulence in the general vicinity of the standing waves, especially around 14 UTC (below).

Terra MODIS Visible (0.65 µm) image, with pilot reports of turbulence [click to enlarge]

Terra MODIS Visible (0.65 µm) image, with pilot reports of turbulence [click to enlarge]