Kevin Laws, science and operations officer at the NWS in Birmingham was on duty during the event and was the main meteorologist issuing the warnings. He invited me, the team on duty that night at the NWS and a few of the newer meteorologists to join in on a discussion about the warning process that day. Jim Stefkovich also attended and he is the meteorologist in charge at the NWS.
We discussed the atmosphere that afternoon... There were a few things going on that limited the development of widespread severe storms. The only zone of real concern developed across parts of east Mississippi and southwest Alabama. We had the wind shear and now we had the instability which storms could feed off of. While the NWS was busy tracking storms moving towards west Alabama, I was as well inside of the Storm Tracker.
Kevin loaded radar data from earlier that day when the storms became tornadic across parts of east Mississippi. The storm heading for Scooba, MS had a long history of producing tornadoes and was definitely the storm to watch as it slowly approached Sumter and Pickens County.
While I was getting in better position to meet up with the tornadic storm to get a visual on it, Kevin was trying to decide when the issue a tornado warning and how large of an area should he extend the polygon warning. Kevin knows the storm has cycled twice but will it do it again and produce another tornado as it gets close to Alabama? Radar scans come in every two minutes, but did he really want to wait another 2 minutes to issue a tornado warning just to see how the storm was developing?
Reports are coming in that a tornado is on the ground in Scooba and Kevin needs to decide whether or not to issue a tornado warning and how much of Sumter and Pickens county to include in the warning. Will the storm turn right? Will it continue northeastward? Will it never cycle and just weaken after the next scan? Will issuing a warning too soon create a false alarm? Did you know that even though the polygon warning may only include a tiny portion of a county that the entire county gets a tornado warning alert? Weather radios and sirens go off for an entire county even if a small portion of the county is under a warning. Is it unnecessary to warn all of Sumter county or do you pull the trigger?
We discussed what we would do if we were in his shoes... We all decided it was definitely worth including a small portion of Sumter county in a tornado warning just in case the storm were to turn right and in case the strong inflow and circulation would clip the northwestern portion of the county.
At this point, I am in the Storm Tracker and heading southwest on highway 17 to get in position to view the mesocylone. It's the part of the storm that is rotating and where a tornado typically forms. The NWS continues to not only pay attention to what the radar products are indicating with the storm but also what is being shared on TV and social media. They see video captured by Brett Adair and myself of the tornado on the ground and growing into a wedge as it tracks towards Aliceville. Radar imagery also showed debris and that this was developing into a strong and dangerous tornado.
Velocity data in the image on the right above shows data dropping out and all sorts of colors which signals to the meteorologists that this isn't just an ordinary tornado that it's strong. Correlation coefficient which detects debris is showing colors on the scale indicative of heavy damage occurring. Now Kevin needs to decide whether or not to change the message in the warning to say considerable or catastrophic. This storm didn't quite meet the criteria for a tornado emergency but with the tornado heading towards Carrollton, Kevin pulled the trigger due to the population of the city and the threatening storm approaching. Based on CC values he knows that this tornado is picking up large objects and a confirmed large and destructive tornado was on the ground.
The storm continued to remain strong and intact and the next step for Kevin was to extend the warning. How many counties should be included in the warning? Remember that a small portion of 1 county alerts the entire county. Kevin decided to include parts of 4 counties in the next tornado warning. He also had to keep an eye on the additional storms exhibiting some rotation back into Mississippi.
While the main storm weakened with time, the storms lining up and moving in across west Alabama needed to be watched closely. The line started to exhibit QLCS (quasi-linear convective system) characteristics and strengthening with meso vortices developing. You can see inflow in green increasing across western Pickens County in the image below.
2 minutes later the circulation tightened up and likely at this point a tornado is developing or on the ground. The NWS quickly issues a tornado warning for Pickens County.
The kind of spin ups associated with a QLCS happens quickly and they don't last long like they do with supercell thunderstorms. The spin up might show up for a scan or two at best and then be done with. You can briefly see a debris signature on the left image below and a tight circulation on the right image below. What's interesting is the fact that the tornado touched down where radial blocking from a cell tower in Columbus is located. If you didn't understand radar meteorology, you might miss the debris signature.
There is so much involved and a lot to consider when you are the meteorologist issuing the warnings. Much respect for the NWS meteorologists that have a tough and live saving job to do!
Stay safe as we approach the spring tornado season!
Know what county you live in and have multiple ways of receiving weather warning information.
Jill Gilardi WBRC First Alert Certified Meteorologist