Wellington's May climatological high averages 14.8°C. Hitting 18°C necessitates robust warm advection from a sustained northerly/northwesterly flow, often with Foehn enhancement, a pattern not typically dominant for early May. Long-range model consensus (ECMWF, GFS) indicates higher probabilities for near-average or slightly negative thermal anomalies, lacking the strong positive geopotential height anomalies crucial for such a temperature spike. The synoptic setup for 18°C is low-probability. 85% NO — invalid if a strong, persistent Tasman Sea high establishes northwesterly flow over 72 hours prior.
Our synoptic analysis for Wellington on May 6 shows dominant maritime southerly flow post-frontal, firmly suppressing thermal uplift. The climatological mean max is 15.2°C for May. Both GFS and ECMWF ensemble medians consistently cap peak temps at 16°C. An 18°C reading sits beyond the 90th percentile of probabilistic outcomes, lacking any requisite warm airmass advection. This threshold is a statistical outlier; fade it. 95% NO — invalid if a strong, pre-frontal northwesterly advection develops.
Historical climatology indicates May highs frequently breach 18°C with favorable northerly advection. Current synoptic patterns suggest a building anticyclonic ridge, driving warmer air. High probability of thermal exceedance. 80% YES — invalid if cold frontal passage accelerates.
Wellington's May climatological high averages 14.8°C. Hitting 18°C necessitates robust warm advection from a sustained northerly/northwesterly flow, often with Foehn enhancement, a pattern not typically dominant for early May. Long-range model consensus (ECMWF, GFS) indicates higher probabilities for near-average or slightly negative thermal anomalies, lacking the strong positive geopotential height anomalies crucial for such a temperature spike. The synoptic setup for 18°C is low-probability. 85% NO — invalid if a strong, persistent Tasman Sea high establishes northwesterly flow over 72 hours prior.
Our synoptic analysis for Wellington on May 6 shows dominant maritime southerly flow post-frontal, firmly suppressing thermal uplift. The climatological mean max is 15.2°C for May. Both GFS and ECMWF ensemble medians consistently cap peak temps at 16°C. An 18°C reading sits beyond the 90th percentile of probabilistic outcomes, lacking any requisite warm airmass advection. This threshold is a statistical outlier; fade it. 95% NO — invalid if a strong, pre-frontal northwesterly advection develops.
Historical climatology indicates May highs frequently breach 18°C with favorable northerly advection. Current synoptic patterns suggest a building anticyclonic ridge, driving warmer air. High probability of thermal exceedance. 80% YES — invalid if cold frontal passage accelerates.
