Current climate: September 2017

September was characterised by lower than normal sea level pressure over the Tasman Sea and New Zealand, which resulted in regular bouts of rainfall moving across the country. This included an event on 6 September which produced heavy rain that trapped two tourists in their car in Waitomo.

Rainfall

September rainfall was well above normal (>149% of the September normal) or above normal (120-149% of the September normal) for large swaths of the North Island, including much of Waikato, western Bay of Plenty, Auckland, Manawatu-Whanganui, parts of Gisborne and Hawke’s Bay, much of the northern half of the South Island, along with eastern Otago and western Southland. Below normal rainfall (50-79% of the September normal) was observed in central and southern Hawke’s Bay, central Otago, and eastern Southland.

Temperature

September temperatures were near average (-0.50°C to +0.50°C of the September average) across large swaths of the country. Temperatures were above average (+0.51°C to +1.20°C of the September average) in parts of Auckland, Coromandel, northern and central Waikato, Gisborne, Hawke’s Bay, southern Manawatu-Whanganui, northern Marlborough, northern Canterbury, and much of Otago. Well above average temperatures (>1.20°C of the September average) were observed in small pockets of Hawke’s Bay, central Canterbury, and central Otago.

Sunshine

September sunshine hours were near normal (90-109% of the September normal) for much of the country. Above normal sunshine (110-125% of the September normal) was observed in parts of western Waikato and northern Manawatu-Whanganui, with below normal sunshine (75-89% of the September normal) in the lower North Island, interior Canterbury, and interior Otago. Isolated pockets of well below normal sunshine (<75% of the September normal) were observed in Wairarapa and central Canterbury.

Soil Moisture

As of 1 October 2017, soil moisture levels were near normal for a majority of the country. Soil moisture was slightly higher than normal for some coastal areas from Blenheim to Dunedin, as well as isolated pockets in Hawke’s Bay and near Cape Reinga. Soil moisture was lower than normal in southern Hawke’s Bay and Central Otago.

Departure from average air temperature for September 2017.
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.
Percentage of normal rainfall for September 2017.