NIWA Seasonal Climate Outlook: Sept, Oct, Nov 2013

NIWA Seasonal Climate Outlook: Sept, Oct, Nov 2013

Overview

The equatorial Pacific Ocean as a whole remains in a neutral state (neither El Niño nor La Niña), although colder than normal (La Niña-like) sea temperatures persist in a shallow surface layer in the eastern equatorial Pacific. International guidance indicates that ENSO-neutral is the most likely outcome for the next three months (September–November).

In the New Zealand region, higher pressures than normal are forecast south of the country, while lower pressures than normal are expected from Queensland eastwards. This circulation pattern is expected to produce more northerlies or north-westerlies affecting the North Island, and a weaker than normal westerly flow over the South Island.

After a very warm winter, the coming spring is likely to have near or above average temperatures across the country. However, frosts and snow conditions may occur in some areas from time to time in early spring. Sea surface temperatures are forecast to be above the climatological average for the coming three months around New Zealand.

Outlook Summary

September to November temperatures are most likely (50% chance) to be above average in the east of the North Island and the north of the South Island, compared with near average (30% chance) or below average (20% chance). In all other regions, spring temperatures are equally likely (40% chance) to be above average or near average.

Rainfall totals over the September – November period as a whole are equally likely (40% chance) to be in the near normal or above normal range for the north and west of the North Island and for Nelson-Marlborough, compared with below normal (20% chance). In the east of the North Island, and west of the South Island, spring rainfall totals are more likely (35-40%) to be in the near normal or below normal ranges than in the above normal range (25%). In the east of the South Island, near normal rainfall is slightly more likely (40% chance) than other categories.
Soil moisture levels are most likely to be normal or below normal (35-40% chance in each category) in the east of the North Island, near normal (40% chance) in the north and west of the South Island, and normal or above normal (35-40% chance) in other regions.

River flows are most likely to be normal or below normal (35-40% chance in each category) in the east of the North Island, slightly more likely to be normal or above normal (35%) in the north of the North Island, and most likely near normal (40-45%) in all other regions.

For regional information see attachment
SCOSept.pdf

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