The latest 00z GFS and 12z ECMWF deterministic runs for April 30 in Wellington are signaling robust warm advection. We are tracking a consolidating Tasman Sea high-pressure system extending a dominant northwesterly flow over the lower North Island, funneling warmer air into the region. Both primary models print maximum temperatures firmly above 16°C: 17.2°C from ECMWF and 16.9°C from GFS. Critically, upper-air soundings indicate strong geopotential height rises at 500hPa, signaling subsidence warming, which will suppress cloud development and enhance boundary layer heating. The GFS Ensemble Prediction System (EPS) shows a compelling 78% probability of exceeding 16°C, with the ensemble mean holding at 17.1°C. The dominant NW gradient will drive a significant foehn effect across the Tararuas, directly impacting the Wellington thermal profile. Expect clear afternoon skies, maximizing diurnal thermal gain. This pattern is unequivocal for a robust afternoon spike. 90% YES — invalid if the Tasman high tracks significantly further south, altering advective flow to more southerly quadrants.
The latest 00z GFS and 12z ECMWF deterministic runs for April 30 in Wellington are signaling robust warm advection. We are tracking a consolidating Tasman Sea high-pressure system extending a dominant northwesterly flow over the lower North Island, funneling warmer air into the region. Both primary models print maximum temperatures firmly above 16°C: 17.2°C from ECMWF and 16.9°C from GFS. Critically, upper-air soundings indicate strong geopotential height rises at 500hPa, signaling subsidence warming, which will suppress cloud development and enhance boundary layer heating. The GFS Ensemble Prediction System (EPS) shows a compelling 78% probability of exceeding 16°C, with the ensemble mean holding at 17.1°C. The dominant NW gradient will drive a significant foehn effect across the Tararuas, directly impacting the Wellington thermal profile. Expect clear afternoon skies, maximizing diurnal thermal gain. This pattern is unequivocal for a robust afternoon spike. 90% YES — invalid if the Tasman high tracks significantly further south, altering advective flow to more southerly quadrants.
