Outlook and outcome – February 2004 to April 2004
Mean atmospheric pressure was below average to the south of New Zealand as predicted, but wind patterns were more southwesterly than expected, bringing lower than average air temperatures over the country.
Rainfall was well predicted in most places.
Although April was a dry month over much of the country, a sequence of severe February floods gave exceptionally high February-April streamflows for most of the North Island apart from the Bay of Plenty, East Cape, and northern Hawke’s Bay regions, where normal or above normal flows occurred. In the South Island, February-April river flows were above normal in the Buller region and normal to above normal elsewhere.
The outcome maps shown here give the tercile rankings of the rainfall totals and mean temperatures that eventuated for these months. Terciles were obtained by dividing ranked February to April 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. (Click to enlarge)
As an approximate guide, middle tercile rainfalls 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.