B737-800
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
ATC Issue All Types; Inflight Event / Encounter Wake Vortex Encounter
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action
Environment - Non Weather Related; Procedure
Approximately 80 miles before top of descent MIA Center descended us to FL360 behind a widebody which was left at FL380. There was a quartering left tailwind of approximately 30-35 knots. We were given 280 knots assigned for spacing. The widebody entered the STAR from our left or the east. Our separation grew from less than 10 miles to just at or slightly over 10 miles with our descent and speed. At approximately 60-55 miles from the new top of descent from FL360 we experienced a rapid roll to the left of approximately 30 degrees. I turned off the autopilot and the plane then rolled right rapidly; about 20 seconds later. We [asked] for a speed of 250 [kts]. ATC gave the speed when we reported the wake turbulence. I continued to hand fly for a while until we could assure ourselves the wind dropped a bit and our separation had increased. I had the FO (First Officer) call the FAs (Flight Attendants) everything was secure and everyone was okay. We had them take their seats [and] the seatbelt sign was on at the time of the event. Upon leveling at 8;000 [feet] and turning westbound we had a second event even though the 777 was turning base ahead and we were just entering the downwind and crossing the bay. Approach had kept the 777 high and gave them relief on the restrictions as they descended. The next day; MIA Approach cleared us to 8;000 [feet] behind an aircraft ahead with tight spacing. We did get a slight roll left then right but I immediately slowed to 230 and had the FO tell MIA we were slowing. This time the aircraft ahead was not kept high and so I hand flew slightly above VNAV path to assure at FL230 we would not have wake turbulence. Later [that day] Tower cleared us to takeoff before [another air carrier aircraft] had rotated. After I lined the jet up on the centerline and after takeoff clearance; we waited 8-10 seconds for [the other air carrier aircraft] to rotate. We then took off. We were given heading 105 [on departure; and the other air carrier was given heading 120]. The aircraft behind us was given 090. We encountered wake turbulence behind [the other air carrier aircraft] due to crosswinds. MIA has minimized separation and rushed operations such that it is my experience safety is impacted.First; the next time MIA says keep it rolling and cleared to takeoff; I will ask to exit when an aircraft is still not near rotating. Second; MIA needs to review the operating practices in play. Lack of separation at FL380; being placed below and behind a heavy with a quartering tailwind; 10+ miles separation was not enough with 30+ knot tailwind. Change the practice of [descending] a non-heavy behind and below a heavy to descending the heavy below the following aircraft.
B737 Captain reported encountering wake turbulence on descent into MIA.