Date: 201908
Local time of day: 1801-2400
Location: ATL.Airport, GA
Flight conditions: Mixed
Weather elements / visibility: Thunderstorm; Turbulence
Light: Dusk
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ATL
ATC / advisory: Center ATL
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Time Pressure; Communication Breakdown; Workload
Anomaly: Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted
Contributing factors: Human Factors; Weather
Primary problem: Weather

Narrative: As we rolled out on final for a Runway 9R at ATL; it became apparent we would not be able to keep the field in sight due to a cell located on final. We requested; and transitioned to an ILS already briefed. There were cells all around the area; but were not warned of any impacting finals. As we got closer; I noticed very heavy rain coming out of the bottom of the cell contacting the ground. It was intense; thick; and ugly; stereotypical of microbursts I have seen in experience and pictures. The radar backed up what we were seeing. I told my FO (First Officer) and Jump Seater there was no way we were going to be able to safely fly through that cell. We were handed off to Tower as I was discussing a go-around and potential windshear; and a bolt of lightning lit up the cell in front of us. I told my FO to tell Tower we were going around. As we began our go-around; we encountered some moderate chop and rain. The Controller told us to continue flying the localizer inbound/maintain runway heading; and I got on the radio and said we couldn't; and were turning right to avoid the weather. I believed this was the safest course of action; as the cell was centralized on final; I was exercising my emergency authority; and looking at the TCAS showed no traffic to our right; while my FO visually cleared right. Our hands were pretty full flying the aircraft. ATC asked if we initiated the turn on our own. I responded we did because we couldn't safely fly through that cell.We were given a heading of 180 and an immediate climb to 4000 ft.; and were handed off to Approach. We heard ATC announce a windshear alert showing a 20-knot loss. Checking in with Approach; they gave us headings away from the field in a box pattern. Approach gave us a number to call on the ground. We asked how long it would be before we were sequenced back in. Approach said Tower had told him it would be at least an hour until we accepted back in. I told him we didn't have fuel for that; and he said he was just the messenger; passing on what Tower told him. I asked him to pass on to Tower there was no way we could have flown through that cell safely; and had to make an emergency deviation for weather. (I was exercising my Captain's Authority.) He said he'd pass it on; and continued to give us headings.We began to coordinate with Dispatch on our divert plan to ZZZ. After coordination; we approached our bingo fuel; and with no hope of Tower letting us into ATL; we asked for and received clearance to ZZZ. Diverting to ZZZ was normal.I should have immediately said to Tower on my turn; I am executing an emergency deviation for weather; turning south now. What altitude and heading do you want this would have made my exercise of emergency authority clearer.We should have been warned of the weather developing on final by ATC. I believe we were punished by Tower for exercising our emergency authority. Tower saying they wouldn't accept us for at least an hour; forcing us to fly box patterns until our gas ran down; forcing us to divert. ATC should work with us in the interest of safety. Tower attempting to force us to fly through a cell that in my experience; had the potential to result in a horrific incident. My FO and I used RRM (Risk and Resource Management) to safely bring our flight to a safe stop at the gate in ZZZ. I am grateful for our training and my FOs professionalism.




Synopsis: B737-800 Captain reported exercising emergency authority to avoid significant weather with reported windshear advisories in the area.