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This is a thread about a fantastic warning decision by NWS Charleston SC, issued on a rapidly evolving QLCS, providing lead time on a significant tornado. (1/9) https://twitter.com/BSHolloway/status/1249860438432546817
We start at 5:45 AM with a kinked-up segment of a quasi-linear convective system (QLCS) in Screven County, Georgia. Several pockets of 50-60 knot inbound winds, but no immediate tornadic concern. (2/9)
Over the next 8 minutes, things change. A marked outflow surge develops. Ahead of it, there's roughly a 20 knot gain in storm-relative inflow. My ILN colleagues have heard me call this "denting the inflow." Clear sign of increased convergent rotation near the ground. (3/9)
But it's not just what's going on near the ground that's important. KCLX shows us the convergence at 2kft, but KCAE shows us a mature, strong mesocyclone in the mid levels.
Convergent rotation sitting under a meso in a favorable tornado environment? That's bad news. (4/9)
Convergent rotation sitting under a meso in a favorable tornado environment? That's bad news. (4/9)
Tornado warning was issued (5:54 AM) and sure enough, that convergence developed into a tornado, on the ground for several minutes northeast of Newington, GA.
Tornadogenesis was anticipated /before/ a circulation appeared on the lowest slice. This is good work. (5/9)
Tornadogenesis was anticipated /before/ a circulation appeared on the lowest slice. This is good work. (5/9)
First tornado dissipated as it crossed into SC, but the fundamentals did not change. Inflow continued to strengthen, as did the mesocyclone aloft. Tornadogenesis on the big one occurred at ~6:10 AM. ~16 minutes of lead time on the initial touchdown. This is GREAT work. (6/9)
What happened next was obviously very hard to watch. An intense tornado developed in this QLCS-embedded supercell, with a TDS height of over 20kft, and fatalities in Hampton County SC. The early warning, though, hopefully saved many more lives. (7/9) https://twitter.com/thegreatzo/status/1249648069538279424
One other interesting radar note. You can track the debris from the first tornado as it gets caught up and blown downwind in the intense outflow surge -- eventually connecting to the RFD from the second tornado. (8/9)
Bottom line: in an incredibly quickly evolving QLCS situation, NWS Charleston SC used sound science and knowledge of previous storm evolution to get a warning out well ahead of a deadly tornado. This stuff isn't easy, and they did a remarkable job. (9/9)
