April Climate Summary

April Climate Summary

Overview

April 2014 was characterised by higher pressure than normal to the southeast of New Zealand with lower than normal pressures over the Tasman Sea. This pressure pattern resulted in north-easterly quarter wind flow anomalies for most parts of the country, with the exception of the north of the North Island, where lower pressures in the Tasman resulted in anomalous north-westerly airflows.

In terms of rainfall, April featured a much welcome change for many areas of New Zealand, chiefly the North Island. Many areas that were in desperate need of rain received above normal (120 to 150% of normal) or much above normal (more than 150% of normal) rainfall for the month. This was echoed for a large part of the South Island, however there the rain was not so welcome for most locations. This is particularly true for parts of the Tasman, Nelson, Canterbury and Marlborough regions where the wet April followed a wet March. For some locations, the rainfall was exceptional compared to normal with three to five times the April normal falling at some of the aforementioned areas.

As noted above, the surplus of rain was quite beneficial for many as soil moisture levels across much of the North Island responded nicely. For example, entering into the month of April soil moisture was considerably drier than normal. However, in response to the described rainfall distribution, soil moisture levels at the beginning of May have recovered to levels much closer to normal, with some locations now observing wetter than normal soils for the time of year. Having said that, there still remains regions of the North Island, chiefly about parts of Northland and northern Auckland, which have soil moisture levels that remain drier than normal. Soils remain abnormally wet for this time of year from the Tasman east through the Marlborough regions and south into much of Canterbury region.

It was an abnormally warm month for a significant part of the country with much of the North Island experiencing mean temperatures well above average (more than 1.2°C above April average). There were only a handful of locations on the North Island that experienced normal (within 0.5°C of April average) with no locations reporting below average temperatures (0.5 to 1.2°C below April average). The South Island also experienced a warm April. However, while well above average temperatures were common, especially for the west coast of the South Island, they were not as extensive for the island as a whole. Still, outside of that area, above normal or normal temperatures were recorded for much of the South Island. Unlike the North Island, there were a few isolated pockets of below normal mean temperatures observed for the month. The nation-wide average temperature in April 2014 was 14.5°C (1.1C° above the 1971-2000 April average from NIWA’s seven station temperature series which begins in 1909).
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