The NIWA and MetService assessment of named tropical cyclone (TC) activity indicates 8 to 10 named TCs could occur in the Southwest Pacific basin between November 2020 and April 2021. This seasonal outlook is for normal to below normal activity in terms of overall named cyclone systems in the region.
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.
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.
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 May (through the 30th) was -0.11˚C, the smallest anomaly since July 2020. The Southern Oscillation Index (SOI) was +0.5, in the ENSO neutral range.