Climate

The NIWA and MetService assessment of named tropical cyclone (TC) activity indicates 9 to 12 named TCs could occur in the Southwest Pacific basin between November 2021 and April 2022. The seasonal outlook is for normal to slightly above normal activity in terms of overall named TCs in the region

A mild and wet September

The NINO3.4 Index anomaly (in the central Pacific) during September was -0.23˚C. Compared to this time last year, conditions are about 0.5˚C warmer. The Southern Oscillation Index (SOI) was +0.8 during September, on the La Niña side of neutral. Notably, the three-month average SOI was +1.0, in La Niña territory.

The NINO3.4 Index anomaly (in the central Pacific) during August was -0.17 ̊C. The Southern Oscillation Index was +0.5. While both remained in neutral territory, other indicators trended toward La Niña.

New Zealand’s second consecutive warmest winter on record

A warm finish to winter for most of the country

Spring rainfall is most likely to be below normal in the east of the North Island, near normal in the west of the South Island, and about equally likely to be near normal or below normal in all remaining regions across Aotearoa New Zealand.

The NINO3.4 Index anomaly (in the central Pacific) during July was 0.08 ̊C. The Southern Oscillation Index was +1.7, firmly in La Niña territory.

Heavy downpours and unseasonable warmth

Temperatures are most likely to be above average in all regions of the country. More northwesterly air flows will likely cause spells of unseasonably warm temperatures in the north and east of both islands in particular.

The NINO3.4 Index anomaly (in the central Pacific) during June was 0.18 ̊C, the first time it has been positive since July 2020. The Southern Oscillation Index was +0.4, in the ENSO neutral range.

New Zealand’s warmest June on record

NZ’s weather patterns are expected to feature substantial week-to-week variability over the coming months, owing to an ENSO neutral state in the tropical Pacific Ocean.