Color-enhanced wind speeds observed from Synthetic Aperture Radar (SAR) data on the second RADARSAT Constellation Mission satellite (RCM-2), shown above in AWIPS (Click here for a similar image online at this website) show parallel lines of enhanced wind speeds, a wind structure suggestive of a bore (click here for many previous blog posts on this phenomena), over southern Lake Michigan. Peak wind values (in yellow over the water) are near 14 m/s, with minima in between the lines showing winds around 5-6 m/s. (Note that SAR wind information over land is invalid). When this kind of event happens under mostly clear skies, parallel lines of clouds (that are perpendicular to the observed wind) develop. In this case, widespread clouds prevented satellite detection of cloud bands. The toggles below show Visible (Band 2, 0.64 µm) and Infrared (Band 13, 10.3 µm) at the time of the SAR observations.

Modest convection (cloud tops are only around -48^oC) over central Lake Michigan likely generated the bore. For a bore to propagate, a strong inversion is required. Soundings at Green Bay WI and Gaylord MI likely are unrepresentative of the environment over southern Lake Michigan. The sounding at White Lake Michigan — near Detroit — (from this website) does show a surface inversion, as does the sounding at Davenport IA. The cool late-Spring waters of Lake Michigan will serve to anchor a similar low-level inversion over the Lake; bore features travel along those inversions.

This NOAA/OSPO website shows regions where SAR data are available each day. SAR data can also be imported into AWIPS, as shown in the animation above, which animation has the SAR data overlain on top of GOES-17 Band 7 (Shortwave IR, 3.9 µm) data. Note that SAR winds are not valid over the land — the stronger returns over the islands are instead telling you something about the surface. (Compare this image to a Landsat image — there’s a good correlation!)

A zoomed-in version of the imagery over the ?Alenuih?h? Channel between the Big Island of Hawai’i and Maui is shown below as a toggle between the 3.9 µm and the winds. The significant funneling between the two islands is readily apparent, with winds increasing from about 15 knots northeast of the Big Island to closer to 25 knots within the channel.

A zoom-in over Maui and Molokai, below, details winds around those islands as well, with strong winds between Molokai and Lanai, and an apparent col to the lee of Maui.

Farther north, over the open Pacific to the north of the Hawai’ian Islands, SAR data shows enhancements in wind underneath structures that are apparent in the Band 7 imagery!