Severe thunderstorms developed over northeast Illinois late in the afternoon on 9 August, and a series of tornadoes resulted. Storm Reports (from the Storm Prediction Center) are shown below. The mp4 animation above (click here for a large animated gif) shows 1-minute GOES-16 Mesoscale Sector 2 visible imagery (0.64 µm) from 1900 UTC on 9 August through 0040 UTC on 10 August. The active convection is apparent.

Part of the region hit by severe weather is in a persistent drought, as shown below (an image from this website). Rains that accompanied the severe weather provided some drought relief. (Click here for hourly CMORPH2 precipitation estimates from RealEarth)

RCM3 (RADARSAT Constellation Mission 3) Synthetic Aperture Radar (SAR) winds from a 2340 UTC overpass on 9 August (from this site) show a wind feature over Lake Michigan associated with the convection. These wind estimates might be affected by ice within the glaciated clouds

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Tropical Storm Mirinae, shown above, to the east of Japan (click here to see the same image with latitude/longitude lines), was overflown on 8 August by Radar Constellation Mission Satellite one (RCM-1) at 2013 UTC. The Synthetic Aperture Radar (SAR) imagery (from this site) is shown below, with both polarities. The two polarities help mitigate wind speed errors that might arise from ice. A peak wind of nearly 60 knots is indicated.

The storm profile winds from the Mirinae at this time are shown below (courtesy Christopher Jackson, GST/NOAA). Such plots are useful for determining max wind radii.

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GOES-16 Mid-level Water Vapor (6.9 µm) and “Clean” Infrared Window (10.35 µm) images, with pilot reports of turbulence plotted in cyan/yellow [click to play animation | MP4]

GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) and “Clean” Infrared Window (10.35 µm) images (above) revealed the formation of transverse banding along the eastern periphery of a decaying Mesoscale Convective System in the Upper Midwest during the morning hours on 07 August 2021. Transverse banding is a satellite signature that usually indicates an enhanced potential of turbulence (reference)— and there were indeed multiple reports of light-to-moderate turbulence within the 26-50,000 feet altitude range (cyan).

CIMSS Scientists have used machine-learning to create a predictive tool for moderate-or-greater (MOG) turbulence based in part on satellite imagery. The product for 1405 UTC on 7 August is shown below. A maximum is anchored on the MCS. This product is available online here. Training for this product is here.

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Synthetic Aperture Radar (SAR) winds are derived from a microwave signal pinged from a satellite; backscatter is converted into winds (given a background field that is typically from a numerical model). The wind structure here is suggestive of a bowing feature to a convective downdraft. How does it compare to radar or satellite imagery? GOES-16 Satellite imagery for the hour bracketing the imagery above is shown below. Convection (weak) is apparent moving east from the tip of Keewenaw peninsula.

What did radar imagery look like at this time? The imagery below, courtesy Nick Langlieb, the SOO at WFO Marquette, shows radar echoes (base reflectivity) at a different level than the Lake-surface values sampled by SAR, so a direct comparison is a challenge (click here to see Correlation Coefficient at the same time). It’s peculiar that no radar signal is apparent to match the strong SAR winds just offshore from the tip of the Keewenaw peninsula (between 88º and 87.5º W) — although there is a feature oriented north-south a small distance to the west of the peninsular tip; there seems to be a better (but not exact) match with the SAR winds near 87º W.

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