ProbSevere (version 3) is an online tool that is available at this link. It gives the probability that the designated radar object will product severe weather in the next 60 minutes, and it was designed to be used in conjunction with other radar, satellite and model data to increase confidence in warning issuance. It is available online here; ProbSevere (version 2) is also online — and available within AWIPS. The RealEarth-based readout, above, shows the radar object that produced the EF-3 Tornado in Gaylord. (Click here for the NWS Gaylord writeup). ProbSevere values were consistently high with the radar object thoughout the trek across the northern Lower Peninsula of Michigan. Here is an image showing the accumulated ProbSevere values across northern Michigan (from this RealEarth link)

Read-outs of PSv3 and PSv2 values are available at this link, and the plot for the radar object in the animation above (#170831) is shown below (Here is a permanent link that allows you to view values!). Of note here is that PSv2 values are larger than PSv3 values. This is because PSv3 is better calibrated. For example, the Gaylord Tornado has a ProbTor value (plotted in red) of 90%! However, it is not the case that ProbTor (version 2) predictions with values of 90% lead to tornadoes 90% of the time: ProbTor v2 is overpredicting values in that case. ProbTor (version 3) is better calibrated, and the lower values are more in line with observations. Users familiar with ProbTor version 2 will need to adjust their expectations when transitioning to ProbTor version 3 (or indeed from any of the ProbSevere version 2 products to ProbSevere version 3 products).

NOAA-20 overflew the region of severe weather just before 1800 UTC (link). Gridded NUCAPS fields from this site, below, show marked instability over the northwestern Lower Peninsula of Michigan, especially in the 700-500 mb layer, where gridded values exceed 7 C/km. The gridded values also show a decrease in stability for any storms moving into the Lower Peninsula from the west; however, Quality Control flags (shown below in a toggle with 850-mb Temperature), show profiles that did not converge over Lake Michigan.

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A benefit of the CSPP Geosphere site is that long animations can be constructed that don’t include every image. The animation above (link) shows hourly true-color (daytime) and Night Time microphysics RGB (nighttime) from 1801 UTC on 18 May 2022 to 2001 UTC on 20 May 2022. This is achieved after clicking on the date in the upper right corner of the image by adjusting the ‘stride’ to — in this case — every 12th image, and increasing the number of frames viewed. The animation above shows a Mesoscale Convective System (MCS) generating over the High Plains late in the day on 18 May and developing into a Mesoscale Convective Vortex (MCV) that persists through late in the day on 20 May 2022 over the mid-Atlantic States. It is unusual for MCVs to persist through the night.

For a MCV to persist, certain environmental conditions must be present. In particular, atmospheric wind shear should be small, and moisture and instability should be greater than normal. In this way, convection can be continually generated to help sustain the cyclonic vortex. The stepped animation below shows 6-h HRRR forecasts (from this website) of Most Unstable Convective Available Potential Energy (CAPE), Total Precipitable Water, and 0-6 km shear, valid at 1800 UTC on 19 May (when the MCV was over central Missouri) and 0600 UTC on 20 May 2022 (when the MCV was over Ohio). The region near the MCV center has small values of shear, and large values of moisture and instability.

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The true-color animation above, produced from the CSPP Geosphere site, shows bore-like cloud features over northern Lake Michigan shortly after sunrise on 20 May 2022. These parallel lines of clouds are mostly likely to persist in regions where a low-level inversion is present. NUCAPS profiles from the 0800 UTC overpass of NOAA-20, shown below, show an inversion below 850 mb over the central parts of the Upper Peninsula of Michigan. The cold waters over the lake would likely amplify the strength of this inversion. The Green Bay soundings from 1200 UTC (here, from this site), also shows a low-level stable layer.

Thanks to Rick Mamrosh, WFO GRB, for bringing these cloud features to our attention! Check out the link on their Facebook page.

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Synthetic Aperture Radar imagery can give very high-resolution observations of winds in regions where wind observations are otherwise sparse (or non-existent). The image above and below show data from an ascending pass of Canada’s RADARSAT Constellation Mission 2 (RCM2) satellite. These data are available online (click here for the image above, and here for the image below), but netcdf files can also be inserted into AWIPS for a direct comparison to other satellite imagery. The image above shows the increase in wind speeds (about 11 m/s) associated with a broken line of cumulus clouds, with stronger winds over the northwest part of the SAR domain. The later image, below, farther north, shows generally stronger winds, and it also shows local wind maxima out in front of cloud formations (in the southeast corner of the SAR domain).

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