December 2018 was characterised by slightly lower than normal pressure over the North Island and higher than normal pressure over the South Island. This pressure set up was associated with more easterly winds than normal.
Temperatures were well above average (> 1.20°C above average) for the regions of Southland, the West Coast, Nelson, as well as large parts of Otago, Tasman, Manawatu-Whanganui, Waikato and the Bay of Plenty. Temperatures were near average (-0.50°C to +0.50°C of average) along the coastal fringes of eastern Marlborough and Canterbury as well as for Gisborne through to Masterton. Elsewhere temperatures were above average (0.51-1.20°C above average).
Rainfall was well above normal (>149% of normal) for the majority of the North Island with the exception of Taranaki and parts of Northland and Manawatu-Whanganui where rainfall was near normal (80-119% of normal). Rainfall was also well above normal for Marlborough and northern Canterbury while the remainder of the South Island saw largely below normal (50-79% of normal) rainfall.
As of 1 January, soils were significantly wetter than normal for the time of year across large parts of the eastern and inland South Island, as well as large parts of the North Island. Soil moisture levels were lower than normal for the time of year in Nelson, Tasman, Southland, the New Plymouth district and parts of the West Coast.
Departure from average air temperature for December 2018.
End of month water balance in the pasture root zone for an average soil type where the available water capacity is taken to be 150 mm.