Analysis of 00Z and 12Z GFS/ECMWF operational runs indicates a robust transient ridging pattern developing west of the Tasman Sea, vectoring a predominant zonal to slight northwesterly flow component over the North Island for April 27th. Surface pressure gradients show an initial weak frontal passage followed by a rapid post-frontal warming trend facilitated by increasing insolation and advection of warmer air from the Tasman. Upper-level geopotential heights are slightly above climatological mean, preventing significant troughing that would usher in cold southerly air. Wellington's typical April mean maximum is 17.3°C. The 14°C threshold is well below this climatological average. Current model ensemble mean for central Wellington peaks at 15.8°C, with 80% of members exceeding 14°C, implying strong thermal support. Expect peak afternoon temperatures to comfortably clear the mark. This is a clear YES signal. 90% YES — invalid if a sudden southerly change develops from an intensifying Tasman Sea low.
