Airbus Industrie Undifferentiated or Other Model
Dispatch Dispatcher
Communication Breakdown
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem
Weather; Human Factors
At XA35z; Dispatch received a pirep via voice from Aircraft X regarding Popocatepetl volcanic ash. Crew reported seeing volcanic ashes at FLXA0 and stayed at FL120 for approximately 40nm to remain underneath the layer.Dispatch immediately notified other Dispatcher and walked over to The Weather Channel WSI rep inside IOC.  Gave IOC WSI rep a pictorial screenshot of Aircraft X.  VAAC and the local government had a forecast for volcanic ashes from SFC-FL200.  WSI had elected to remove their SIGMET a few hours prior.Dispatch had the webcam up and noticed that even though WSI had removed their forecast; Popocatepetl has still emitting sporadic emissions.  All flights inbound and outbound from MEX had been given thorough briefs regarding the volcano activity and even given recommendations to remain at lower flight levels based upon past WSI SIGMETS; volcanic VAAC forecasts and pireps from inbound flights.AT XA47z; WSI wrote a volcanic ashes SIGMET that went directly over the field.  Dispatch began the process of implementing the volcanic ashes Fallout Checklist as per the DPM.  Five minutes later; WSI writes another volcanic ashes SIGMET that no longer sits over the airport.Dispatcher immediately notifies the Chief Dispatcher of the disparity.  While in the presence of the Chief; the IOC WSI rep also briefs the Chief about Popocatepet and admits that they decided to change the forecast off the field.As per one of the screenshots attached; the WSI SIGMET is 3nm east of the airport.  Aircraft X observed and reported the volcanic ashes immediately after takeoff.  The volcanic ashes is in fact within 10nm of the airport.As per FAA/NOAA Key to Aerodome Forecast (TAF) and Aviation Routine Weather Report (METAR) ; a TAF and SPECI METAR should have been issued to indicate volcanic ashes since the observation was made within those parameters (5-10nm or 8; 000 meters of the airport).  WSI is not putting out an accurate product.This is not the first time; Dispatch has observed WSI writing volcanic ashes SIGMETs just a 'hair' outside the terminal airport and in direct conflict with what the VAAC and government forecast. For the [two days]; WSI was the only weather source forecasting MEX airport to be in the clear.WSI (for unknown reasons) refuses to write a volcanic ashes SIGMET over the airfield or update TAF's to reflect the volcanic ashes within vicinity of the airport.
Airline Dispatcher reported disparities between current volcanic ash activity in the airport vicinity and active SIGMET utilized for airline operations.