Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Situational Awareness; Time Pressure
Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Weather / Turbulence
Flight Crew Became Reoriented
Procedure; Environment - Non Weather Related; Software and Automation
BHM ATIS advised runways 6 and 36 were active; with visual and RNAV approaches in use to both. Conditions were VMC with good visibility. Upon initial contact with BHM Approach; we were advised to expect Runway 6. The First Officer briefed a visual approach to be backed up with the RNAV Runway 6. As we approached the terminal area; we observed a single heavy rain shower cell located directly on the final approach course for Runway 6; very near the final approach fix. This cell was approximately 5 NM wide and ATC had advised two other aircraft that this weather contained 'light to heavy' precipitation. It seemed to us that if we were to continue to pursue the approach for Runway 6; we would most likely fly through this weather.After brief discussion; the First Officer and I determined that an approach and landing to Runway 36 would keep us clear of that weather. BHM Approach agreed and vectored us for an RNAV approach to Runway 36. The First Officer briefed the RNAV 36 approach and I entered the landing data for Runway 36; including current ATIS reported winds - 110 at 6 kt. The approach proceeded normally with the aircraft configured normally for landing and in a stable condition. The First Officer had switched off the autopilot at just below 1;000 ft. and maintained the proper glide path with the 'snowflake' showing on glide path. At some point just below DDA; 1;530 ft.; and MDA; 1;480 ft.; very near the ridge just south of the airport; we received a terrain caution with [a] 'too low terrain' audible message. The First Officer adjusted pitch and we went very slightly above glide path momentarily. We received no additional warnings or cautions and the First Officer readjusted pitch to resume normal glide path. Touchdown on Runway 36 was normal and within the touchdown zone. At no time did we receive any 'pull up' or 'obstacle pull up' alerts; only the one 'too low terrain' alert. At the time of alert; the FO (First Officer) responded in accordance with the note in [the] POH Bulletin XX-XX; X.X.X. Conditions during the event were day VMC with good visibility; 10 SM.I believe this terrain caution could have been avoided by not performing an approach to Runway 36 in the first place and by maintaining a profile slightly above glide path. I did not observe us ever being below glide path. In thinking about the event afterwards; I realize that while the charted procedure guarantees obstacle clearance down to the MDA; it is the pilot's responsibility to maintain visual clearance from terrain and obstacles once below MDA. In the case of this particular approach; doing that requires one to fly a profile above a normal glide path. I had always known about the ridge and antennas south of the airport; but had never flown an approach to Runway 36 in BHM. Despite it being a charted procedure which is permissible in day VFR conditions; I'm not convinced that it is an approach that I would use in the future - due to the need to maintain a higher than normal glide path in order to avoid the terrain alert. In my opinion; flying a steeper approach could potentially lead to other issues such as landing long or past the touchdown zone if not managed very carefully. In the future; I would likely only use Runway 36 if in an emergency if Runway 6/24 was not available.
Captain reported triggering a low terrain alert while flying below the normal glide path profile during an approach to the runway.