Lake Michigan MesovortexGOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a well-defined mesoscale vortex (or “mesovortex”) moving southward across southern Lake Michigan on 31 December 2017. The default western GOES-16 Mesoscale Sector provided images at 1-minute intervals. This feature was responsible for brief periods of heavy snow at locations such as South Haven, Michigan KLWA (beginning at 1455 UTC), Benton Harbor, Michigan KBEH (beginning at 1625 UTC) and La Porte, Indiana KPPO (from 2055 to 2115 UTC).
Comparisons of POES AVHRR/Terra MODIS/Suomi NPP Infrared (10.8 µm/11.0 µm/11.45 µm) and Visible (0.86 µm/0.65 µm/0.64 µm) images along with an overlay of the corresponding Real-Time Mesoscale Analysis (RTMA) surface winds (below) provided views of the mesovortex at 1522 UTC, 1714 UTC and 1852 UTC, respectively.During the preceding nighttime hours, a comparison of Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0729 UTC along with an overlay of 07 UTC RTMA surface winds (below) showed in spite of patchy thin cirrus clouds over the region, ample illumination from the Moon (which was in the Waxing Gibbous phase, at 96% of Full) enabled a signature of the early stage of mesovortex formation to be seen on the Day/Night Band (DNB) image. Ice crystals within the thin cirrus clouds were responsible for the significant scattering city light signatures on the DNB image. As an aside, it is interesting to note that ice could be seen in the nearshore waters of Lake Michigan — both in the western part of the lake, off the coast of Wisconsin and Illinois, and in the eastern part of the lake off the coast of Lower Michigan. The lake ice appeared as darker shades of cyan in the 250-meter resolution Terra MODIS false-color (Band 7-2-1 combination) Red-Green-Blue (RGB) image from the MODIS Today site (below).