Current Climate - September 2013

September 2013 was characterised by much lower pressures than normal around much of the New Zealand region, except for an area of higher pressures than normal to the east of the North Island, and another area of high pressure well to the south of the country. This pressure pattern caused more west to southwest flows across New Zealand. These unstable flows caused numerous storms and fronts to affect the country in September, including a severe wind storm in Canterbury early in the month.


Patchy rainfall anomalies were observed throughout the country in September, with well above normal rainfall for the time of year (more than 150 percent of September normal) observed in parts of Northland, Auckland, Waikato, Bay of Plenty, Gisborne, Manawatu, Wellington, Marlborough, inland Canterbury, and Fiordland. Above normal rainfall (120 to 149 percent of September normal) was experienced at other locations within these regions. In contrast, below normal rainfall (50 to 80 percent of September normal) was observed in south Canterbury and Central Otago. Near normal rainfall (within 20 percent of September normal) was observed elsewhere. As at 1 October, most soils around the country were at normal soil moisture levels for the time of year. In Hawke's Bay, around Gisborne, Kaikoura, and Blenheim, soils were wetter than normal for the time of year.


Well above average temperatures (more than 1.2°C above September average) were experienced in Hawke's Bay and inland Gisborne in September. It was the warmest September on record for Masterton. Above average temperatures (0.5-1.2°C above September average) were recorded for most of the remainder of the North Island, except for the Far North, Wellington, and western Waikato, which experienced near average temperatures (within 0.5°C of September average). Most of the South Island recorded near average September temperatures, except for Nelson and Blenheim (above average) and Dunedin and parts of Central Otago (below average; 0.5-1.2°C below September average). The nation-wide average temperature in September 2013 was 11.0°C (0.6°C above the 1971-2000 September average from NIWA's seven-station temperature series which begins in 1909).


September was a very sunny month for Westland (well above normal sunshine totals, more than 125% of September normal). In contrast, below normal sunshine (75-90 percent of September normal) was experienced in Northland, parts of Wellington, Wairarapa, inland Canterbury, and Central Otago. Near normal sunshine hours (within 10 percent of normal September sunshine hours) were recorded elsewhere. 

Percentage of normal rainfall for September 2013.
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.
Departure from average air temperature for September 2013.