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Sample Forecast for New Zealand

Summary for New Zealand

Synopsis: El Niño is expected to remain strong through the Southern Hemisphere summer 2015-16, with a transition to ENSO-neutral anticipated during late autumn or early winter 2016.

A strong El Niño continued during November as indicated by well above-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean. The Niño-4, Niño-3.4 and Niño-3 indices rose to their highest levels so far during this event, while the Niño-1+2 index remained approximately steady. The subsurface temperatures in the central and eastern Pacific, while still well above average, decreased slightly due to the eastward push of the upwelling phase of an equatorial oceanic Kelvin wave. Low-level westerly wind anomalies and upper-level easterly wind anomalies continued over the most of the tropical Pacific. The traditional and equatorial Southern Oscillation Index (SOI) values remained negative. These conditions are associated with enhanced convection over the central tropical Pacific and suppressed convection over Indonesia. Collectively, these atmospheric and oceanic anomalies reflect a strong El Niño episode that has matured.

Most models indicate that a strong El Niño will continue through the Southern Hemisphere summer 2015-16, followed by weakening and a transition to ENSO-neutral during the late autumn or early winter. The forecaster consensus remains nearly unchanged from last month, with the expectation that this El Niño will rank among the three strongest episodes as measured by the 3-month SST departures in the Niño 3.4 region dating back to 1950. El Niño is expected to remain strong through Southern Hemisphere summer 2015-16, with a transition to ENSO-neutral anticipated during the late autumn or early winter 2016.

North Island

Temperature

January

Almost all of the North Island should be near normal to slightly above normal.

February

Almost all of the North Island should be near normal.

Precipitation

January

From Northland to Wellington and across to Taranaki and east to East Cape it should be near normal to slightly drier than normal. Only the east coast from Gisborne through Hawkes Bay and eastern Wellington should be near normal to in isolated places slightly wetter than normal. The eastern Waikato and Bay of Plenty should be slightly drier than normal with some isolate areas perhaps moderately drier than normal.

February

Near normal to slightly wetter than normal across nearly the entire island with slightly wetter parts in far Northland and East Cape through Hawkes Bay and eastern Wellington. Slightly drier in the volcanic plateau.

South Island

Temperature

January

Almost all of the South Island should be slightly to moderately above normal. The Canterbury Plains and the far southeast and West Coast should be near normal.

February

Almost all of the South Island should be near normal.

Precipitation

January

Most of the northern half of the island should be near normal except for the Alps that should be slightly drier than normal. The southern half of the island should all be slightly drier than normal.

February

Slightly drier than normal on the West Coast and the remainder of the island near normal.