Large Transport
Dispatch Dispatcher
No Specific Anomaly Occurred All Types
General Flight Cancelled / Delayed
Company Policy; Human Factors; Weather
Took over flight from previous shift. Flight was delayed due below minimum weather at destination (KRNO). Weather was KRNO 06XA55Z 00000KT 1/16SM R16R/1800V2600FT FZFG VV002 M03/M04 A2971. (RNO needs 2400 on the RVR). Previous shift dispatcher told me Captain wanted to go as he believed he had an improving weather trend. I reviewed the weather and made calls to RNO tower to get current RVR. RNO weather sequences: SPECI KRNO 06XB07Z 00000KT 1/16SM R16R/1600V2000FT FZFG VV002 M03/M04 A2971 KRNO 06XB55Z 30003KT 1/16SM R16R/1600V2000FT FZFG VV002 M04/M04 A2969 SPECI KRNO 06XC15Z 31003KT 1/16SM R16R/1600V3500FT FZFG VV002 M03/M04 A2969 KRNO 06XC55Z 00000KT 1/2SM R16R/P6000FT FZFG BKN002 BKN100 M03/M04 A2969 At approximately XC45Z noticed a definite improving trend and spoke with RNO tower to get current RVR on the recorded telephone tape. XC55Z sequence verified tower observation. Flight filed at XD16Z. Flight departed for RNO. Flight landed safely at RNO at XD20Z.
The weather in RNO was forecast ¼ SM until XD00Z. METARs had reported 1/16 SM visibility for most of the night. The flight was scheduled to arrive in KRNO at XC15Z. The crew called me to discuss the weather in RNO. I told Captain that the weather did not meet the minimum requirements to leave for KRNO. I discussed with him the 90 minute rule that applied with an above minimums forecast and a below minimums current. This would be the situation if we delayed 45 minutes. I told him that it would require a positive trend and agreement on both our parts that all indications were that KRNO weather would be at or above minutes at arrival. I told him we would keep in touch and when the weather showed a positive trend; after the delay; we would be able to launch. The previous METAR was a slight improvement in the RVR over the XX55Z METAR; but still showed 1/16 SM. I was not in agreement that all factors indicated the weather would be up for his arrival and therefore I would not authorize departure. The RVR quickly dropped again; SPECI KRNO 06XB07Z 00000KT 1/16SM R16R/1600V2000FT FZFG. He finally agreed to wait for improved weather and I handed over the flight at about XC05z. The weather at the time was still KRNO 06XB55Z 30003KT 1/16SM R16R/1600V2000FT FZFG. At XC55z; the weather went to ½ SM and my relief confirmed the RVR was good with the tower and told the crew they could depart. The weather continued to improve and the flight landed without incident.
The Captain thought that the weather was improving and that it would be at or above minimums at the ETA and therefore it was legal to depart; while the Dispatcher did not. The Dispatcher held the flight until the weather improved to minimums.