Flight crew reported departing with RVR under minimums.

Attributes
ACN	1713167
Time
Date	201912
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	Mixed
Light	Dawn
Aircraft 1
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Takeoff
Flight Plan	IFR
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 68 Flight Crew Total 276 Flight Crew Type 276
Person 2
Function	First Officer Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 178 Flight Crew Total 3714 Flight Crew Type 1326
Events
Anomaly	Deviation - Procedural Published Material / Policy Inflight Event / Encounter Weather / Turbulence

Narrative:

Initial takeoff out of ZZZ. Reviewed weather and noted that ZZZ1 was designated as takeoff alternate. Briefed both first officer and lead of the takeoff alternate. ATIS stated that RVR was 500 but continuously being updated. Tower was calling RVR of 1200 due to ground fog. First officer and I briefed both his minimums for takeoff as well as reviewed the back of the airport diagram page. Airport diagram page stated with adequate visual reference we needed 1600 or 1/4 mile. Taxiing out watched other aircraft depart as the ground fog was quickly burning off. As we approached number one tower stated 'RVR is 1400 v 3500'. They did not provide a base RVR and I did not ask. We informed tower we were ready when they were. Tower cleared us for takeoff and I stated to the first officer that visibility was good and that I could see the departure end of the 9000 ft. [Runway]. My estimate was visibility was greater than 2 miles. We took off uneventfully and shortly thereafter atis stated visibility was 3 miles. On climb out; first officer and I discussed weather and reports. Upon inquiry into the fom; it seems that we should have either queried tower for specific RVR or delayed takeoff until all numbers were above 1600. Also; I was lulled into a VFR mindset because in hindsight what I was physically seeing did not match the min RVR tower stated.

Original NASA ASRS Text

Title: Flight Crew reported departing with RVR under minimums.

Narrative: Initial takeoff out of ZZZ. Reviewed weather and noted that ZZZ1 was designated as takeoff alternate. Briefed both FO and Lead of the takeoff alternate. ATIS stated that RVR was 500 but continuously being updated. Tower was calling RVR of 1200 due to ground fog. FO and I briefed both his minimums for takeoff as well as reviewed the back of the Airport Diagram page. Airport Diagram page stated with adequate visual reference we needed 1600 or 1/4 mile. Taxiing out watched other aircraft depart as the ground fog was quickly burning off. As we approached number one Tower stated 'RVR is 1400 v 3500'. They did not provide a base RVR and I did not ask. We informed Tower we were ready when they were. Tower cleared us for takeoff and I stated to the FO that visibility was good and that I could see the departure end of the 9000 ft. [Runway]. My estimate was visibility was greater than 2 miles. We took off uneventfully and shortly thereafter atis stated visibility was 3 miles. On climb out; FO and I discussed weather and reports. Upon inquiry into the FOM; it seems that we should have either queried Tower for specific RVR or delayed takeoff until all numbers were above 1600. Also; I was lulled into a VFR mindset because in hindsight what I was physically seeing did not match the min RVR Tower stated.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.