Retrospective - September to November Outlook

The climate we predicted and what actually happened.

Seasonal predictions for September to November 2010 correctly indicated above normal mean sea level pressures near New Zealand, for spring as a whole, with pressures at least 4 hPa above seasonal normal over the Tasman Sea and New Zealand. 

Predicted rainfall: Rainfall is likely to be near normal in most regions, averaged over the three months of spring (September, October, November). The north and east of the North Island is likely to experience normal or above normal rainfalls, according to the Centre’s latest seasonal outlook.

Outcome: September was a wet month in many areas, but a very dry October and November followed, so that spring rainfall totals were in fact near normal across much of the South Island (excluding Nelson City, south Canterbury, northern and central Otago, where rainfalls were below normal). Spring rainfall totals were below normal for Northland and Auckland (an incorrect forecast), and above normal for parts of Gisborne, southern Hawkes Bay and the Tararua Districts (correctly forecast).  Elsewhere in the North Island, spring rainfall was indeed in the near normal range (between 80 and 120 percent of seasonal normal).   

Predicted air temperature: Temperatures are likely to be above average across the whole country. However, short-term cold snaps typical of spring will still occur from time to time.

Outcome: Spring temperatures were above average for the bulk of the South Island (excluding an area of normal temperatures in the Buller and Gray Districts).  Temperatures were above average in the greater Bay of Plenty/Waikato region, and around New Plymouth and Palmerston North, but in general were near normal elsewhere in the North Island.