Current climate: January 2016

During January 2016, strong El Niño conditions continued in the Tropical Pacific. However, rather than the typical south-westerly flow anomaly over New Zealand that is associated with El Niño at this time of year, high pressure anomalies to the east of New Zealand, as well as to the south and west of the South Island caused northeast flow anomalies over the North Island and southeast flow anomalies over the South Island in January.

Rainfall

The moist tropical air masses (including ex-tropical cyclones Ula and Victor) that affected New Zealand brought significant rainfall. Rainfall totals for January were well above normal (>149% of January normal) in northern and eastern regions of both Islands. Notably, Timaru received almost three times its normal rainfall for January (296% of January normal rainfall), with over half of that occurring in one day (81 mm, the highest 1-day rainfall total for January in Timaru, in records going back to 1881). Rainfall was above normal (120-149% of January normal) for many other locations in the North Island. Few locations recorded below normal (50-79% of January normal) or well below normal (<50% of January normal) rainfall in January – this only occurred in isolated parts of Taranaki Region and Queenstown-Lakes District.

Temperature

The northeast flow anomaly over the North Island during January caused warm and humid tropically-derived air masses (including two ex-tropical cyclones) to affect New Zealand during the month. Above average (+0.51°C to +1.20 °C above the January average) and well above average (> +1.20 °C above the January average) temperatures were observed for the entire Island, as well as the north and west South Island. In contrast, the predominant southeast flow anomaly over the South Island caused below average (-1.20°C to -0.51°C below the January average) or well below average (<-1.20°C below the January average) temperatures for the east and south of the South Island. The nation-wide average temperature in January 2016 was 17.6°C (0.6°C above the 1981-2010 January average from NIWA’s seven station temperature series which begins in 1909).

Sunshine

Sunshine was near normal (90-109% of January normal) or below normal (75-90% of January normal) for the North Island in January. Sunshine was below normal or well below normal (<75% of January normal) for the South Island. The wet and stormy conditions across much of the country during the month caused sunshine totals to be lower than normal for most places.

Soil Moisture

At the end of December 2015, soil moisture levels were extremely low for many parts of the country, particularly in the North Island and the north and south of the South Island. However, numerous rainfall events throughout the country in January alleviated soil moisture deficits, and as of 1 February 2016, soil moisture levels were above normal for the time of year for eastern Northland, Coromandel, northern Hawke’s Bay and Gisborne, as well as northern Tasman, Nelson, and coastal Canterbury. Drier than normal soils were present in the remainder of the North Island, south Tasman, Otago and Southland. Near normal soil moisture conditions were evident elsewhere.

Departure from average air temperature for January 2016.
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 January 2016.