Outlook and outcome – November 2001 to January 2002
Normal to above normal rainfall was predicted in the north of both islands and near normal elsewhere. Rainfall was above normal in most regions, with near normal totals in the southwest South Island.
Temperatures were expected to be above normal over northern and western North Island regions, and nearer normal elsewhere. This was correct for most regions except the southwest of South Island where temperatures were higher than normal.
A gradient was predicted in river flows from normal to above normal flows in the north to below normal in the south. Flows were above normal everywhere except in inland Otago and Southland.
The three outcome maps (right column) give the tercile rankings of the rainfall totals, mean temperatures, and river flows that eventuated for November 2001 to January 2002. Terciles were obtained by dividing ranked November to January data from the past 30 years into three groups of equal frequency (lower, middle, and upper one-third values) and assigning the data for the present year to the appropriate group.
As an approximate guide, middle tercile rainfalls (33.3 to 66.7%) often range from 80 to 115% of the historical average. Middle tercile air temperatures typically occur in the range of the average plus or minus 0.5 °C.
Note that in the maps above, the upper, middle, and lower tercile ranges are described by the terms Above normal, normal, and Below normal, respectively.