Retrospective - January to March Outlook

A moderate La Niña was expected to persist over the January to March season – this was indeed the case with a 3-month SOI of around +0.5.  Mean sea level pressures were accurately forecast – these were projected to be above normal across the South Island, but below average to the north of New Zealand.  More north-easterly air flows than normal over the North Island were forecast; more frequent easterly winds were observed.

Predicted rainfall: Rainfall totals are likely to be above normal throughout the North Island, and normal or above normal in the north of the South Island. For the west, south and east of the South Island, late summer rainfall is likely to be below normal or normal.  Soil moisture levels and river flows are likely to be above normal in North Island regions, normal or above normal in Nelson-Marlborough, and below normal in the west, south and east of the South Island.

Outcome:  The outlook indicated above normal seasonal rainfall for all North Island regions.  This was a generally correct forecast, with almost all North Island regions experiencing at least 120 percent of seasonal rainfall - the exceptions being northern Northland, the Bay of Plenty, much of the Waikato, and Wanganui to Palmerston North, which experienced closer to normal seasonal rainfall. Normal or above normal seasonal rainfall was correctly projected for the Nelson and Marlborough regions. Below normal or normal rainfall was predicted for the remainder of the South Island for January - March.  This was a correct projection for Westland and Fiordland (with below normal seasonal rainfall observed), as well as much of Canterbury and coastal Southland (near normal seasonal rainfall observed); but it was a very wet season (i.e. wetter than forecast) for south Canterbury, Otago, and inland Southland.

Predicted air temperature: Air temperatures are likely to be above average throughout the North Island and in the north, west and south of the South Island. In the east of the South Island, temperatures are likely to be average or above average.

Outcome: Temperatures were much cooler than forecast for all regions of the country. Average or below average temperatures were observed over parts of Northland, coastal Bay of Plenty and the west of the South Island. Below average (lower tercile) temperatures were experienced in all other regions.