Visible imagery from near sunset on 16 May 2023, above, shows multiple horizontal cloud lines north of the islands of Oahu and Kauai. Each of the clouds lines is associated with a local modulation of the wind field in the SAR Wind field. The wind /Normalized Radar Cross Section fields are also available online (winds; NRCS). Note that a SAR Wind scene from this ascending Sentinel-1A pass (here) that was taken just before the one above has an hourglass-shaped feature (at 21.2^oN, 158.4^oW) in the derived wind field that is highlights a mismatch between the first guess field used and the NRCS data.

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Southern Wisconsin experienced the convergence of 3 cooling mechanisms during the afternoon hours of 16 May 2023: (1) the arrival of a dense band of smoke aloft — transported southward from wildfires in Alberta and Saskatchewan — which reduced incoming solar radiation, (2) a southward-moving cold front and (3) the inland surge of a lake breeze (or “Pneumonia Front“) from Lake Michigan. Signatures of all 3 features were evident in GOES-16 (GOES-East) True Color RGB images from the CSPP GeoSphere site (above), with the cold front and lake breeze marked by broken lines of cumulus clouds that could be seen through the thick veil of smoke.

In a comparison of GOES-16 Day Land Cloud RGB images at 1826 UTC that include readouts of Aerosol Optical Depth (AOD), MVFR Fog Probability, Land Surface Temperature and Fire Temperature derived products for a point beneath the thick smoke layer (above) and just south of the thick smoke layer (below), the degree to which the smoke was reducing the amount of incoming solar radiation was apparent in a reduction in Land Surface Temperature (78.26ºF beneath the thick smoke where the AOD was 2.08, vs. 83.98ºF just south of the thick smoke where the AOD was negligible). Both points — and the W-E oriented band of thickest smoke — were located south of the approaching cold front (1800 UTC surface analysis).

CIMSS Natural Color RGB images (below) include plots of surface and buoy reports along with frontal analyses — note the significant drop in air temperatures across southeast Wisconsin as the lake breeze moved inland (for example, from the low 80s F to the middle 50s F within a 30-45 minute period at Milwaukee and Racine; further inland, a notable temperature drop was also seen in Madison just after 19:30 or 7:30 PM local time). Water temperatures reported by Buoy 45007 in southern Lake Michigan were in the 44-46ºF range during the day, and just after 1800 UTC the NOAA-20 VIIRS Sea Surface Temperature value over that buoy location was 47ºF.

A plot of lidar backscatter (source) at Madison, Wisconsin (below) depicted increasing smoke within 2 layers: one at an altitude around 3 km, and another within the 5-6 km altitude range.

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True-Color imagery from GOES-East (above, from the CSPP Geosphere site) and GOES-West (below, also from the CSPP Geosphere site) from 1720-1910 UTC show multiple active fires in British Columbia, Alberta and Manitoba, and a wide plume of smoke entrained into a storm centered just north of Saskatchewan (one wonders if the rain from the storm is somewhat muddy) and also moving south of the storm into the atmosphere above the Great Lakes. Drought conditions that have been widespread over Alberta (from this site) likely are contributing to the smoke production (which has been ongoing — see this CIMSS Blog Post from early May).

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TROPICS (Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of SmallSats) satellite observations include microwave data at 12 different frequencies between 91.6 and 204.8 GHz. (Click here for a Satellite Book Club presentation on TROPICS). A TROPICS launch occurred from New Zealand in early May (link), boosting two satellites into orbit; a second launch is pending. In addition, TROPICS Pathfinder launched in 2021 (link), was designed to test TROPICS capabilities (see this blog post), and is still transmitting the data used in this Blog post. The animation above, from a website internal to SSEC, shows TROPICS data over the Indian Ocean from 11 May through 14 May. Land/sea differences are discernible in the 91.6 GHz imagery on top, but not in the 204.8 GHz imagery on the bottom; microwave energy at 204.8 GHz is absorbed by water vapor in the atmosphere.

Storm-centered (and zoomed-in) imagery from TROPICS (204.8 GHz) (courtesy the TROPICS team including Glenn Perras at Nick Zorn at MIT/LL), shown below, is compared from the DSMP SSMI/S imagery (85 GHz) (from this CIMSS Blog Post, courtesy Scott Bachmeier) at nearly the same time. The TROPICS Channel 12 data is more influenced by water vapor in the atmosphere; the SSMI/S 85 GHz data is more affected by scattering by ice. That could account for some differences in the imagery, especially in rain bands. There is excellent overall agreement between the two images, however.

Earlier overpasses over the storm are shown below (images also courtesy of from Glenn Perras and Nick Zorn, MIT/LL). The ongoing organization of the storm between the two times includes the development of a cold brightness temperature ring around they eye. The evolution of the Himawari-9 Clean Window Band 13 (10.4 µm) imagery (at half-hour time-steps) spanning the two times below is here. It also shows increasing organization.

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