Date: 201911
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Anomaly: Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General None Reported / Taken
Contributing factors: Manuals; Human Factors; Company Policy
Primary problem: Ambiguous

Narrative: During preflight preparation for the leg to ZZZ1; we learned that the visibility there had dropped considerably with RVR's at 800 feet steady and freezing fog. I spoke to the gate agent and had folks board on time; expecting the RVRs to vary enough to be able to dispatch. Given the nature of RVRs and how rapidly they change; I thought it best to be ready to go the moment we got the visibility above minimums. However the RVRs were stubborn and were holding steady at 800-1000 feet. I called Dispatch to get a real-time look at the vis and they confirmed RVRs were holding steady. Making PA's to the pax (passengers) and notifying OPS; we opted to remain at the gate with door open and wait for the vis to increase. After about 50 minutes or so; Dispatch called me and told me that the SOC supervisory on duty had informed him to tell us we were legal to depart off of the TAF; which at the time was calling for 1/4SM and OVC001. This is the point where Dispatch and I came to a disagreement. Per the FOM I cannot depart for a station if weather reports or forecasts or any combination indicates weather to be below authorized landing minimums. Furthermore; FOM explicitly states that METARs must be considered if the flights ETA lands within a METARs ETA. Throughout all of training and recurrent training; it has been reinforced to me that we consider any flight less than 1 hour to be within a METARs ETA so this flight at 37 minutes long definitely fell under the METARs jurisdiction. FOM also references using the worst weather condition in any combination of reports or forecasts. Finally; FOM says that the PIC and dispatcher must be in agreement that in order to dispatch; weather conditions at the destination at ETA must be expected to be equal to or better than minutes specified in the Ops Specs (in this case; CAT II). I spoke with the Dispatch Supervisor and informed him the FOM prohibits me from departing due to the worse weather condition found in the METAR; and since the flight is under an hour I'm unable to launch due to vis below CAT II minutes. Additionally; given the RVRs steady nature; I had doubts whether or not we'd be able to actually get in. The Supervisor made the argument that the RVRs had 'been going up and down all day' and that the flight from ZZZ2 was able to launch just fine. I countered with the fact that ZZZ2 was able to launch because they didn't have to consider the METAR for a flight that long; and were able to go off of the 1/4SM and OVC001 in the TAF. I then asked to speak to the on-duty chief to get an interpretation of the FOM; because ultimately I would like to get these people to their destination and if I'm wrong in my interpretation I'd like to know. Upon speaking with the chief pilot; I was told I could launch because I had an alternate listed and the TAF was controlling; not the METAR. I wasn't 100% sold on it but accepted it; and we hung up. At this point the Dispatcher called me back and said they had decided to push the flight back to the next morning due to the late hour and the unwavering RVRs. Coordinated with local Ops at the airplane and began the deplaning process. We learned afterwards that another airline had five different flights trying to get to ZZZ1 that had to divert that night due to the fog. I'd like an interpretation (with the FAA's input) on the FOM regarding METARs and their usability in determining legality to dispatch. Multiple times now I've encountered this situation involving controlling weather on flights under an hour as a Captain and each time I've had to put the brakes on the operation because; while Dispatch and Management say to go; our manuals state we can't. The Dispatch Manual doesn't state anything about METARs being considered if a flights ETA falls within the valid period of a METAR. What is the valid period of a METAR in this context? Looking at various FAA interpretations on FOM online; I can't find a definitive answer to any of these questions. The reg and FOM both say'report OR forecast OR any combination thereof.' Are we allowed to disregard the METAR and combo of reports/forecasts in favor of the TAF because the use of 'OR?'




Synopsis: Air carrier Captain reported different interpretations of FAR weather requirements by crews and Dispatch.