Strong near-surface inversions over the upper-midwest early on 1 June 2019 (as shown by 1200 UTC Skew-Ts at Green Bay, WI, Detroit/WhiteLake, MI and Gaylord, MI) helped support the presence of southward-propagating bore features, as shown in the still image (an animation) of radar imagery above (Courtesy Fred Best, SSEC), and (more subtly) in the water vapor imagery (Courtesy Scott Bachmeier) below.

The pressure sensor at the top of the Atmospheric Oceanic and Space Science Building showed many small time-scale pressure perturbations on this day. (Image courtesy Pete Pokrandt)

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Later in the day, strong convection developed over southwestern Lower Michigan, starting shortly after 2215 UTC.  The visible imagery below shows 1-minute imagery (GOES-16 ABI Band 2, 0.64 µm) from a Mesoscale sector positioned over the convection.  At the start, the parallel lines of low clouds suggest a bore feature is propagating southward towards strong convection over northern Indiana and northern Ohio.  Two things happen when that feature meets the convective outflow: some energy is apparently reflected to the north, but very strong convection rapidly develops near Battle Creek MI, where 2″ hail was observed at 2235 UTC (SPC Storm Reports).

The clean window (GOES 16 ABI Band 13, 10.3 µm) animation during the day, below, show many features suggesting bore/gravity wave propagation over the area. It is challenging to pick out the impulse from this animation that lead to the severe convection that hit Battle Creek.

The Low-Level water vapor animation, shown below, also shows many features that resemble gravity waves or bores, but it also shows a line of parallel features moving towards the site of convective initiation (Consider this short loop from 2126 to 2156 UTC, for example).

For convection to initiate, instability should be present. The graphic below from the Storm Prediction Center mesoanalysis website shows a nose of unstable air (represented by high values of CAPE) encroaching into southwestern Lower Michigan.

GOES-16 Baseline Products can also diagnose instability. On 1 June 2019, however, abundant cloudiness limited the utility of the Baseline clear-sky only products, but AllSky versions have been developed and are available online at this website. The animation below shows the evolution of the AllSky Lifted Index from 1826 through 2356 UTC on 1 June 2019. In agreement with the SPC analysis, the AllSky product shows a nose of instability pushing into southwestern lower Michigan. An southward-propagating impulse (apparent in both visible and low-level water vapor imagery) meeting this gradient in instability did initiate convection on this day.

NOAA/CIMSS ProbSevere (v.2), a tool designed to give confidence that severe weather might occur in the next 60 minutes, shown below, tracked the rapid evolution of the storm. ProbHail increased from 7% at 2220 UTC to 81% at 2230 UTC!

The chart below, from John Cintineo, SSEC/CIMSS, graphically shows the very rapid development of Prob Hail values. Much of the increase in ProbHail was driven by MESH and Total Lightning observations. When an impulse enters a region of instability in a good environment, explosive growth can result.

Many thanks to TJ Turnage, NWS Grand Rapids, for alerting us to this very interesting case.

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GOES-16 (GOES-East) True Color Red-Green-Blue (RGB) images from the AOS site (above) revealed the arrival of a dense high-altitude smoke plume from the north, which cast a late-day shadow onto the top of a more aged layer of lower-altitude smoke over the Upper Midwest on 30 May 2019. These smoke layers were being transported from large wildfires that were burning across northern Alberta.

Images from the west-facing AOSS rooftop camera (below) showed the slow obscuration of the setting sun as the smoke layers aloft became increasingly thick.

The GOES-16 Smoke Detection product (below) flagged most of the lower-altitude smoke with its “High Confidence” category.

The higher-altitude smoke plume that moved southward contained some cirrus debris from the pyrocumulonimbus cloud that formed at the wildfire source in northern Alberta, so it was not classified as smoke by the Smoke Detection product — the plume itself did exhibit 10.3 µm infrared brightness temperatures as cold as -57ºC as it approached the Canada/US border (below).

Some of the lower-altitude smoke exhibited GOES-16 Aerosol Optical Depth values as high as 1.0 to 2.0 (below).

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GOES-17 (GOES-West) “Red” Visible (0.64 µm) images (above) revealed the mesoscale cyclonic circulations of actinoform clouds (or “actinae“) within the marine boundary layer stratocumulus cloud field over the central Pacific Ocean on 30 May 2019.

This type of cloud feature was originally identified in TIROS-V imagery over the Pacific Ocean in 1962 (below), and was featured in the first Monthly Weather Review “Picture of the Month” series in January 1963.

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Due to an overlap of GOES-17 (GOES-West) Mesoscale Domain Sectors, images were available at 30-second intervals — and “Red” Visible (0.64 µm) images (above) showed the development of thunderstorms over southeastern Oregon, southwestern Idaho and northern Nevada on 29 May 2019. Some of these thunderstorms produced heavy rainfall and small hail in southwestern Idaho, and a cold air funnel was spotted in northern Nevada (local storm reports).

A comparison of Visible images from GOES-17 and GOES-15 images (below) helps to underscore some of the improvements in the GOES-R series of satellites over their predecessors — with images every 30 seconds compared to every 4-15 minutes (with gaps of 30 minutes during the Full Disk scans every 3 hours), the short-term convective trends could be better monitored using GOES-17. Also note that the GOES-15 Visible images do not appear as bright as those from GOES-17 — prior to the GOES-R Series of satellites, the performance of visible detectors degraded over time, leading to imagery that appeared more dim as the Imager instrument aged. Visible detectors on the new ABI instrument benefit from on-orbit calibration to remedy this type of degradation.

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