NIWA Outlook: May-July 2014

NIWA Outlook: May-July 2014

Overview

For the coming three months as a whole, mean sea level pressures are expected to be slightly lower than normal over New Zealand with higher than normal pressures to the south-east and lower than normal pressures to the north of the country. These pressure patterns are expected to produce mixed wind flows over New Zealand with perturbed conditions from time to time.

Sea surface temperatures are expected to be near average for the coming three months around New Zealand.

ENSO-neutral conditions (neither El Niño nor La Niña) continued in the equatorial Pacific Ocean in April 2014. Above normal sea surface temperatures along the equator now cover a significant part of the central and far eastern Pacific; and these warm anomalies are consistent with developing El Niño conditions. International guidance indicates that ENSO-neutral conditions are the most likely outcome for May-July 2014. However, following this period El Niño appears increasingly likely with 11 of the 14 models monitored by NIWA predicting El Niño conditions over August-Oct 2014.

Outlook Summary

May–July temperatures are most likely (50% chance) to be average for the west of the South Island, above average (50% chance) for the east of the North Island, and average or above average (40-45%) for all remaining regions of New Zealand. Cold snaps and frosts can still be expected in some parts of the country as autumn advances into winter.

May–July rainfall totals are equally likely (40% chance) to be normal or above normal in the east of the South Island, and most likely (40-50%) to be in the near-normal range for all remaining regions.

May–July soil moisture levels are most likely (40-45%) to be normal or below in the north of the North Island and west of the South Island, likely (35-40% chance) to be normal or above normal in the north of the South Island, and most likely (45-50%) to be normal for all remaining regions.

May–July river flows are equally likely (40% chance) to be normal or below normal in the north of the North Island and west of the South Island, likely (35-40% chance) to be normal or above normal in the east of the North Island and the north of the South Island, and most likely (50% chance) to be above normal in the east of the South Island. Finally, river flows are most likely (45% chance) to be normal in the west of the North Island.
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