Date: 201706
Local time of day: 1801-2400
Location: ZDV.ARTCC, CO
Flight conditions: Mixed
Weather elements / visibility: Thunderstorm
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZDV
ATC / advisory: Center ZDV
Reporter organization: Government
Reporter function: Instructor; Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Time Pressure; Workload; Communication Breakdown; Confusion; Distraction; Fatigue; Human-Machine Interface
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance
Contributing factors: Human Factors; Procedure; Weather
Primary problem: Weather

Narrative: For the initial part of the shift; I was conducting OJTI on a different sector than the ones involved here. A line of thunderstorms started forming about one hour into the shift. Eventually; these storms formed a very solid line from the eastern corner of ZDV; all the way north to Canada; with one small break near O'Neill; NE (ONL). Traffic was sent north over ONL; or south towards Hill City (HLC) and Hays (HYS) KS. I noticed (while conducting OJTI) that sectors 17/18 were unusually busy for the time of day. The volume was much higher due to increased enroute traffic in the south part of our airspace.Our area's departure sector (sector 7) receives DEN departures climbing out of Denver TRACON (D01) airspace on four different SIDs; Two of those feed into sectors 8/67; where I was conducting OJTI. The other two feed into sectors 17/18; to the south; With the line of thunderstorms starting in the far east portion of our airspace and continuing north to Canada; and a small gap still existing up towards ONL; the majority of those departures were asking to head south; towards sectors 17/18; due to the weather. This resulted in congestion and increased complexity in sector 7. 7 was staffed with an RA (Radar Assist) position.The sectors I was conducting OJTI on happen to be adjacent to the FLM desk; in our area. A CIC was on position in the area; as the FLM was on a break. I overheard the CIC make a request to TMU to give sector 7 some in-trail spacing on the DEN departures; due to complexity in sectors 7/17/18. There was discussion back and forth about this point; the gist of it being that the weather was too far away and did we really need it; etc. This is not uncommon - 'push back' from TMU is common when our area makes requests pertaining to the east departure gate. The result was that sector 7 became even more busy/complex; and the requested in-trail spacing was only minimally complied with. Sectors 17/18 got even busier.My trainee and I took a lunch break. During this break; a controller from another area told me that the hole in the weather near ONL had closed up; and indicated that ZMP controllers had 'shut off' Denver Center entirely. Controller told me that all of her area's traffic was now headed south into my area's airspace to go around the south end of the weather; because the alternative was going well north into Canada. Unfortunately; storms had also formed down south of my area's airspace; in Kansas City Center; extending south from the central portion of Kansas; and down all the way toward Texas. Those storms were moving north. This created a very narrow corridor (at the smallest; less than 20 miles wide) between two areas of storms; north of HYS; through which an enormous volume of east-west traffic; DEN departures; and DEN arrivals were all passing. This corridor also ran the boundary with ZKC/ZMP airspace.I returned from the break before my trainee did; and my FLM directed me to offer the next person a break. I went to the first person who was up in the duty list - he was assigned to the 18 RA position. I plugged in and began to monitor the situation; but the 18 RA controller was far too busy to begin a briefing. Sector 18 was busier than I had ever seen it before; with a frequency that was nonstop talking; multiple aircraft blocking almost every transmission; an unsafe volume of aircraft; and each aircraft making multiple requests for deviations and altitude changes. Eventually; I realized that my trainee would be returning; and that the next position up for break was the 17 R (Radar) controller. I told the FLM I was going to get 17 R out; and let my trainee offer 18 RA a break (while my trainee is qualified to work 17 R and 18 R; he is still a developmental; and I believed it would be an overwhelming and unsafe situation for him if he were to plug into a radar position). My trainee returned; plugged into 18 RA; and the controller being relieved ended up staying plugged in as a third person at thesector (18 H).I plugged into 17 R; and the controller wasn't able to give me a full briefing for at least 10 minutes. He stayed behind after I sat at the sector; and functioned as 17 H to provide another set of eyes. The 17 RA position was also staffed. Sector 17 was in much the same situation as Sector 18; next to me. It was a completely saturated sector; the frequency was congested to the point of being almost unworkable; and no aircraft were able to get anything they were requesting; in terms of route or altitude changes. Vertical separation was the only way to get aircraft from one side of the weather to the other. Additionally; every aircraft landing DEN had to be given a new clearance with an appropriate STAR; because those aircraft were coming over from ZKC routed direct HLC; direct DEN. I don't blame ZKC; they were just as busy as we were. Eventually; the 17 H position swapped out. Eventually; the sector calmed down enough for me to release the RA and H controllers to take positions elsewhere; and to combine sectors with 18 and 19 (low altitude). I was sent home for the night shortly after the sector combination.Let me make it abundantly clear that this was an unsafe situation; a very dangerous situation. I was barely able to read data blocks; simply because I had so many in a very small area. Multiple control instructions had to be repeated over and over because I could barely get a word in edgewise. I certainly did not have the time to describe weather to every aircraft in accordance with the 7110.65; and I am certain that ZMP/ZKC airspace was violated numerous times. Our area couldn't split up the affected airspace any more than it already was - we simply had too much volume. One sector/frequency in our area remained unopened and unused; but using two frequencies would have made a bad situation even worse; in my professional judgment. Six people were collectively working sectors 17/18 at any given time during this situation; and it still wasn't enough.In addition to the unsafe situation overall; this was an unsafe situation for every aircraft that was squeezed through that gap in the weather. Aircraft reported up to moderate turbulence; and IMC conditions in several overhangs/cloud layers; passing through the area. The storms were; as indicated by the numerous Center Weather Advisories; capable of hail up to 4 inches; tornadoes; and strong surface winds. As hazardous as these storms were; I'm unable to understand why the default solution seemed to be 'well; we'll just let them all deviate through there and put a couple sectors completely underwater.' It's contrary to everything we are taught in our weather briefings here at the ZDV. I am CIC rated in my area; and the MAP (Monitor Alert Parameter) number for Sector 17 (as well as 18) is 21 aircraft. I don't know what the number actually was; during this scenario; but my EDST (En-routed Decision Support Tools) indicated 52 in the ACL (aircraft list); during the busiest portion. I have never been as busy as I was during this time period. I have never felt that I was working a situation as unsafe as this one was. I admit that I have no working experience in TMU or ATCSCC (Air Traffic Control System Command Center); but I don't understand what on earth went so wrong. I understand that there are planning telecons throughout the day for TMU; as well as the stand-up briefing that management attends twice per day (morning; and mid-afternoon) at ZDV. Weather is a big part of the stand-up briefing at ZDV. This should have been a screaming red flag.This weather was very much in accordance with the thunderstorm forecasts from the National Weather Service; and should not have surprised anyone who was paying attention. Weather is a personal interest and hobby of mine; and I knew coming in for this shift that we had the potential for a difficult swing shift; if the forecast verified. I don't know if any recommended/required routes were issued at any point during theday; pertaining to this weather specifically. Given how saturated we became in my area; I feel as though that probably didn't happen. I don't know if ZDV TMU reached out to any external facilities to try to alleviate the congestion in my area's airspace. Routing even a portion of the en-route east/west traffic further south into Oklahoma/Texas would have been a big help. It seems unlikely; as most traffic was allowed to just deviate through the gap we had in the weather. I don't know if ZDV TMU coordinated with any internal sectors to alleviate the congestion in my area's airspace. Routing a portion of the eastbound traffic from the other parts of ZDV down into western Kansas and northern Oklahoma would have been a big help; also. Again; it seems unlikely; as most traffic was allowed to just deviate through the gap we had in the weather. I don't know why ZDV TMU/D01 TMU were unwilling/reluctant to offer us the requested assistance pertaining to the evening departures coming out of TRACON airspace; knowing that those airplanes all had to go to one point in our airspace. I don't know why some of the east departures couldn't have been swapped to the south departure gate to aim them toward an area more clear of weather. Again; push back is very common when my area asks for assistance with the east departure gate. It makes no sense to me; because when TMU calls with a monitor alert for a busy sector; they ask if we need assistance. I don't know why assistance was so difficult for them in this instance.During the calmer part of the shift; when I was conducting OJTI; my trainee was tasked with several different TMU initiatives; meant to assist/protect ZMP controllers - 25 miles in trail to ORD was one; another was a requirement to have all MSP arrivals below FL330 entering ZMP. We did everything we were asked to do. I firmly believe in looking after my fellow controllers; even the ones I don't physically sit next to. Unfortunately; it doesn't feel like anyone was looking out for us when we actually needed the help.Review ZDV TMU conduct and coordination/activity during this shift. Encourage TMU pro activity in terms of coordinating with internal sectors/external facilities when it's obvious that a sector/area will be dangerously busy. Encourage ZDV TMU to ask the affected area what kind of help they need. Again; they are good at working to accomplish traffic management initiatives for everyone around us; but I feel that sometimes in-house sectors are left by the wayside. Also; encourage ZDV TMU to actually listen to us when we specify what assistance we are requesting. We aren't asking for fun; we're asking because we need the help.Review CWSU (Center Weather Service Unit) forecasts and coordination. Review ATCSCC's actions as they pertain to this shift. Ultimately; we (controllers) need those folks who work in TMU/CWSU/ATCSCC to work well together and protect us to the extent possible; during situations such as this.




Synopsis: ZDV Center Controller reported an unsafe situation due to weather and the Traffic Management Unit not implementing flow for deviating aircraft.