Current Climate - April 2013

April 2013 was characterised by lower pressures than usual over New Zealand and to the south and west of the country, with higher pressures than normal to the east of the Chatham Islands. This meant more northwesterly winds than normal affected the country, resulting in a very warm month for many regions. Northwesterly fronts resulted in extremely heavy rainfall in the western Bay of Plenty on 20 April and in the Nelson and Tasman regions on 21 April.


More than double the normal April rainfall total was recorded in the north of the South Island. Motueka received 267 percent (over two-and-a-half-times) normal April rainfall, with almost half of this occurring in one day, on the 21st (116 mm). Also, Tauranga received almost two-and-a-half-times its normal rainfall for April (284 mm, 236 percent of normal). Rainfall was also well above normal (above 150 percent of April normal) in parts of Waikato, Bay of Plenty, and Manawatu. Rainfall was above normal (120-150 percent of April normal) in parts of: Northland, Auckland, Kapiti Coast, Canterbury, and coastal Southland. In contrast, April rainfall was below normal (50 to 80 percent of normal April rainfall) in central Otago, with some locations recording well below normal rainfall (less than 50 percent of normal April rainfall). As at 1 May, significant soil moisture deficits (more than 110 mm of deficit) were evident in parts of Canterbury and central Otago. The rainfall during April recharged soils throughout most of New Zealand.


Mean temperatures for April were well above average (more than 1.2°C above the April average) across most of the North Island. Mean temperatures were above average (between 0.5°C and 1.2°C above the April average) for most of the South Island except for parts of inland Canterbury and Otago (near average temperatures for April there). It was the warmest April on record for Leigh, Masterton, Gisborne, Wairoa, and Ohakune. The nation-wide average temperature in April 2013 was 14.0°C (0.7°C above the 1971-2010 April average, using NIWA’s seven-station temperature series which begins in 1909).


The dominance of low pressures during April resulted in a cloudy month for the lower North Island and northern and eastern South Island, with below normal sunshine hours for those areas (75 to 90 percent of normal April sunshine hours). In contrast, it was a very sunny month for the West Coast of the South Island, south of Franz Josef (more than 125 percent of normal April sunshine). Sunshine was near normal (within 10 percent of normal April sunshine hours) elsewhere. Of the available, regularly reporting sunshine observation sites, the sunniest four centres so far in 2013 (January to April) are: New Plymouth (1118 hours), Whakatane (1097 hours), Paraparaumu (1006 hours), and Lake Tekapo (1003 hours).

Percentage of normal rainfall for April 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 April 2013.