Date: 201811
Local time of day: 1801-2400
Location: ZTL.ARTCC, GA
Weather elements / visibility: Thunderstorm
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Descent
Second aircraft: Gulfstream IV / G350 / G450
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Confusion; Situational Awareness; Workload; Communication Breakdown
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control
When detected: In-flight
Contributing factors: Human Factors; Procedure; Staffing; Weather; Airspace Structure
Primary problem: Procedure

Narrative: [After many] years of ATC; this was possibly the most unsafe I have ever felt. I was so busy; that I didn't even realize the loss had occurred; nor did my D side; my tracker; or the FLM that was standing behind me most of the session. I only found out the next day because the facility second-in-command called me into his office to discuss the event. There were numerous factors contributing to the event.1. Increase traffic into the sector due to Area 4's arrival being unavailable due to weather. All of the ATL inbounds from FL were routed into the LaGrange sector. This; alone; is not all that rare or that challenging; however...2. There was no in-trail spacing provided by ZJX. Extra volume with zero in-trail is not a recipe for success. I believe in-trail was requested by TMU but I'm not sure how much and why it wasn't followed. 3. The ATL south departures were deviating straight into my sector. This is easily the most important factor in my mind that created the sector saturation. I expressed this to ZTL management after this session and countless sessions in my career until now. I feel like I'm talking to a brick wall. You simply cannot have departures and arrivals to the busiest airport in the world occupying the same 50-100sq miles. It doesn't work; it never will. Yet; it happens all the time and our TMU is either ignorant or willfully negligent. I expressed this concern to [name removed] and was told that TMU prefers to leave this up to the area FLMs. Why? The TMC monitoring the ATL airport can see and anticipate this happening before anyone on the floor. Why wouldn't they solve the problem before controllers are placed in these unsafe situations? Furthermore; our FLM did call TMU to shut off the south departures and the request was ignored (or must have been ignored because it didn't happen). After realizing that TMU was not going to shut off the south gate; the Area 5 FLM told the Area 4 FLM to hold their departures so that they could gain altitude first and then deviate into the LaGrange sector; so that they would be less of a factor. This also did not happen. In fact; the Area 4 FLM came into Area 5 to argue with the Area 5 FLM directly behind me while I was extremely busy.4. Weather. There was a horrible and solid line of thunderstorms spanning across the entire southern portion of ZTL. This was obviously a factor. Foremost because it caused.5. Frequency congestion. As reported; I was working sector 9 and 10 combined; using 2 frequencies. The need for deviations and other requests caused impossible frequency congestion. I have never felt so helpless in my career. I can't do my job it I can't talk to and understand airplanes; plain and simple. The sectors should have been split.6. Staffing. Nobody wants to admit that staffing is a contributing factor to these events. Our negotiated staffing number for thunderstorm season is 12 CPCs. We worked this shift with 10. 10 CPCs is simply not enough to work in the busiest facility in the world when there is weather. If we had more CPC's on shift; the sector would have been split. Period. I know my FLM will come under heat for having it combined; but he/she can only use the resources that he/she has. 7. A80. They are getting harder and harder to work with. I take full responsibility for delivering them 2 airplanes without the appropriate spacing. However; my FLM informed me that they had almost 3000 ft of altitude when I switched them and yet nothing was done to stop the aircraft off to prevent a loss. I cannot confirm this as I have not seen the FALCON and I do not want to see it. Furthermore; A80 decided to shut off our area without providing a reason. Again; this happens all the time. Aircraft come over high on the arrival due to pilot error? Shut off Area 5. Requested in-trail not enough for the controller working in A80? Shut off Area 5. God forbid an aircraft has to be vectored inside the 40 DME? Shut off Area 5. It's ridiculous. We were inan out of holding all night; even at times when we had an entire runway just for our arrivals. Lastly; there was some mention about feeding the GNDLF arrival at 10 miles in trail. That request never made it to Area 5. So we were most likely shut off because we weren't even told the requested in trail. Lastly; 'descending via' while running in-trail is incredibly difficult and nonsense. It's no surprise A80 wants it that way because it's easiest for them. The aircraft are spaced out way more than the arrival rate says they need to be; and they are lower crossing the boundary. Win win for them; lose lose for ZTL. See the common theme? I can't tell you how many times they tell us to run 20 miles in trail to A80 but leave our TBFM [Time Based Flow Management] numbers up and all the numbers are negative. Either they don't need what they ask for (likely) or TBFM is broken. Regardless; someone should stand up to them and say that we can't provide extended in-trail and continue to descend via; especially landing east. The entire system lacks accountability. The system failed me and I was put in a terribly unsafe situation and yet I'm the only one that seems to accept any kind of responsibility. With the management re-org (stupid) there's no one in this building that TMU even has to answer to; not a move that inspires confidence for an improved product.They'll probably come after the FLM for not splitting the sector and justifiably so; but he/she made a judgment call and it was a mistake. What will they do to the contributors that just did nothing? Or the ones that were asked to do something and ignored the request? What about the upper level managers that decide that there's no money in the budget to provide us with the overtime to actually staff the facility appropriately?




Synopsis: Atlanta Center Controller reported an unsafe situation that resulted in a loss of separation.