Aircraft “distrails” over the southcentral US

January 29th, 2007 |

GOES-12 visible image

GOES-12 visible channel imagery (above; Java animation) revealed numerous aircraft dissipation trails (otherwise known as “distrails” or “hole punch clouds”) during the day over eastern Texas, northern Louisiana, southern Arkansas, and Mississippi on 29 January 2007. Corresponding GOES-12 10.7µm InfraRed (IR) imagery showed that cloud top temperatures over that region were generally between -20º and -35º C; as aircraft (likely air traffic to/from Dallas-Fort Worth airport KDFW) penetrated that supercooled cloud layer aloft, they caused the cloud droplets to glaciate and begin to fall out of the cloud (causing the “holes” and “streaks” that were evident on the visible imagery). A higher resolution view of these cloud features is available from the Terra MODIS (sourced from the NASA Rapidfire site) and Aqua MODIS overpasses. The 12 UTC rawinsonde data from Fort Worth, Texas (below) indicated that the likely elevation of the supercooled coud deck was probably around 25,000 feet or so. Photos of these cloud features can be seen on the MediaLine weather forum, Weather Underground WunderBlog, WKRG (Mobile AL), NASA Earth Observatory , and StormCenter Envirocast sites.
Fort Worth TX rawinsonde report

Snow cover in southeastern Virginia and northeastern North Carolina

January 29th, 2007 |

GOES-12 visible image

Around an inch of snow accumulated across parts of southeastern Virginia and northeastern North Carolina during the overnight hours on 28-29 January 2007. This patch of snow cover was evident the following morning on GOES-12 visible channel imagery (above). A Java animation of visible images shows that the northern portion of the snow cover (in Virginia) began to melt rather quickly during the late morning hours. The darker region within the area of snow cover is the Great Dismal Swamp National Wildlife Refuge; snow was not able to accumulate over most of that marshy surface, so it does not appear as white as the surrounding snow-covered land (MODIS true color image). In addition, we can see that the snow cover extended as far to the southeast as coastal sections of the Albemarle and Pamlico Sounds in North Carolina.

By examining AWIPS imagery of some of the MODIS channels, we can confirm that this particular image feature is indeed snow on the ground: snow is a very strong absorber at the 2.1 µm wavelength, and therefore shows up as a dark feature on the Snow/Ice (Band 7) image (below, upper right panel). Note that the MODIS IR brightness temperatures (below, bottom left panel) are several degrees colder in the region of snow cover (-5º to -8º C, darker blue enhancement) than over the surrounding bare ground (0º to -3º C, cyan enhancement).
AWIPS MODIS visible, near-IR, IR, SST images