Current Climate - August 2013

August 2013 was characterised by mean sea level pressure (MSLP) which was much lower than normal across all of New Zealand, with strongly negative anomalies to the south of Australia. In contrast, MSLP anomalies were well above normal to the east of New Zealand. These regional pressure patterns resulted in more frequent northerly and north-easterly flows across the country, resulting in high mean temperatures for the time of year across much of the country.

Rainfall

August was a dry month for southwestern and eastern Southland, as well as parts of South Otago and Central Otago, and the McKenzie Country.  Well below normal rainfall (less than 50 percent of August normal) was recorded at those locations.  Below normal rainfall (50-79 percent of August normal) was recorded in most remaining areas of Southland and Otago, as well as coastal and inland Canterbury south of Christchurch, Wellington, Wanganui and parts of Waikato.  In contrast, August was a wet month for Gisborne and Hawke’s Bay.  Well above normal rainfall (more than 150 percent of August normal) was recorded throughout those regions, with some areas towards the coast recording more the double their August normal rainfall.  Above normal rainfall (120-140 percent of August normal) fell in eastern parts of Northland.  Near normal rainfall was experienced elsewhere (within 20 percent of August normal rainfall).  As at 1 September 2013, most soils throughout New Zealand were at normal soil moisture levels for the time of year.  In isolated parts of Central Otago, coastal North Otago and about Kaikoura, soils were wetter than normal for the time of year.

Temperature

A very warm August was experienced throughout New Zealand.  Mean temperatures for August were well above average (more than 1.2°C above August average) across almost the entire South Island, and most parts of the North Island.  The exception was areas of Northland, Auckland and western Waikato where temperatures were in the above average range (0.5-1.2°C above August average).  Mean temperatures of at least 2.0°C above average for August were recorded in inland parts of Southland, Otago, and Canterbury, as well as Christchurch, Banks Peninsula, West Coast, Manawatu, Taranaki, Bay of Plenty, and Waikato.  The nation-wide average temperature in August 2013 was 10.6°C, (1.9°C above the 1971-2000 August average) from NIWA’s seven-station temperature series which begins in 1909.  August 2013 recorded the highest August mean temperature on record for the seven-station series.

Sunshine

Sunshine hours for August were above normal (110-125 percent of normal August sunshine) for South Otago, and western parts of Southland and Otago. Below normal sunshine (75-90 percent of normal August sunshine) was recorded throughout Nelson, Marlborough, the northern West Coast, Wellington, western Bay of Plenty and parts of Waikato and Auckland.  Near normal sunshine was experienced elsewhere (within 10 percent of normal August sunshine).  Of the available, regularly reporting sunshine observation sites, the sunniest four centres so far in 2013 (January to August) are: Whakatane (1800 hours), New Plymouth (1706 hours), Blenheim (1604 hours) and Lake Tekapo (1591 hours).

Percentage of normal rainfall for August 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 August 2013.