After looking at the Cloud Top Cooling and Divergence, there was a case from MPX where a severe thunder warning was issued across southwest Minnesota. The cloud top divergence overlaid with visible satellite did a really nice job showing areas of deep convection (texture) with areas of divergence. This signal preceded the MESH severe hail by 5 to 10 minutes.

Animated GIF showing a 4-panel plow with visible satellite (channel 2) underlaid on all 4 images. The contrast between the cold and warm hues in the top left was one of the strongest seen of the day. The other 3 panels show cloud top divergence (CTD) with small smooth (top right), medium smooth (lower left) and high smooth (lower right). MESH greater than 1 inch is shown in the lower left as well using the default MESH color curve. Green is > 1 inch hail, an the occasional yellow pixels are >2 inch hail. The white text on the lower right is just a placeholder to mark areas of high CTD at the start of the loop.

Notice the area of high cloud top divergence at the start of the loop (red, center of panels). However, there is not a coarse texture of the clouds indicating a strong updraft. Later on in the loop, you’ll see that same red area overlaid with deep, coarse texture of rigorous updrafts on the southwest part of the storm. This is followed by MESH output of severe hail.

A SVR was issued at 2146Z, MESH shows 2” hail at 2152Z, and the satellite signature preceded both of those.

At 2145Z, 1 minute prior to severe TS warning issuance. There is a strong signal of cloud top divergence colocated with a rigorous updraft. The MESH (green, lower right) had a hail greater than an inch at this time.

At 2152Z, MESH (green, lower right) had a hail greater than 2 inches at this time.

At 2110Z, MESH indicated another small area of hail greater than 2 inches. There were two reports (green dots) of 1.25” hail with this storm near this time.

– Updraft