GREMLIN Goes Over 60dBZ?!

 A very interesting thing happened with the GREMLIN tool with today’s supercell southwest of Wichita Falls, TX. After a very strong upward burst in the updraft and surge in lightning activity, the CONUS GREMLIN actually showed simulated returns over 60dBZ, despite the product supposedly having a hard cap at that level. Simulated returns as high as around 64dBZ were noted.

Fig. 1. Clockwise from top left:GREMLIN GOES-East Meso1; MRMS Composite Reflectivity; GREMLIN GOES-East CONUS; GOES-East Meso1 Channel 13 10.35µm IR imagery.

Looking at the loop before and leading up to this time (Fig. 2), we see persistent high overshooting tops in the IR imagery, and even evidence of gravity waves surrounding propagating away from the core of the overshooting top. The Mesosector GREMLIN was a bit less and jumpy, but did eventually show consistently stronger simulated returns. Meanwhile, the CONUS GREMLIN would continue to consistently show strong returns at least approaching 60dBZ even after this loop. The GLM Flash Extent Density (Fig. 2 overlay) does show higher values in the frames leading up to GREMLIN going over 60dBZ.

Fig 2. Same as Fig 1, for a loop from 2024z to 2035z.

Fig 3. Same as Fig 2, with GOES-EAST GLM flash extent density overlaid.

- Marko Ramius