Current ECMWF extended-range and GFS operational runs for Wellington on May 10 exhibit a probability distribution overwhelmingly centered on 13-16°C. 850hPa temperature forecasts indicate a persistent cool-to-neutral baroclinic zone, with no significant warm advection signature originating from the Tasman Sea or a dominant northerly anticyclonic ridge. Climatological data underpins this: the 95th percentile daily maximum for May is ~18°C, positioning 20°C as a +2 sigma event. While localized foehn effects can enhance temperatures, the necessary ambient airmass warmth and upper-level support for a 20°C reading at sea level are consistently absent across all major model suites. Ensemble means firmly project maximums below the 17°C threshold, signaling a low-probability outlier. 98% NO — invalid if all major models flip to +2 sigma anomaly by T-72h.
Current ECMWF extended-range and GFS operational runs for Wellington on May 10 exhibit a probability distribution overwhelmingly centered on 13-16°C. 850hPa temperature forecasts indicate a persistent cool-to-neutral baroclinic zone, with no significant warm advection signature originating from the Tasman Sea or a dominant northerly anticyclonic ridge. Climatological data underpins this: the 95th percentile daily maximum for May is ~18°C, positioning 20°C as a +2 sigma event. While localized foehn effects can enhance temperatures, the necessary ambient airmass warmth and upper-level support for a 20°C reading at sea level are consistently absent across all major model suites. Ensemble means firmly project maximums below the 17°C threshold, signaling a low-probability outlier. 98% NO — invalid if all major models flip to +2 sigma anomaly by T-72h.
