Summary for New Zealand

Synopsis: El Niño will likely peak during the Southern Hemisphere summer 2015-16, with a transition to ENSO-neutral anticipated during the late autumn or early winter 2016.

A strong El Niño continued during October as indicated by well above-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean. Most Niño indices increased during the month, although the far eastern Niño-1+2 index decreased, accentuating the maximum in anomalous SST farther west. The subsurface temperature anomalies also increased in the central and eastern Pacific, in association with another downwelling equatorial oceanic Kelvin wave. Low-level westerly wind anomalies and upper-level easterly wind anomalies continued over the western to east-central tropical Pacific. Also, the traditional and equatorial Southern Oscillation Index (SOI) values remained negative. These conditions are associated with enhanced convection over the central and eastern tropical Pacific and with suppressed convection over Indonesia. Collectively, these atmospheric and oceanic anomalies reflect a strong and mature El Niño episode.

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

North Island

Much of the North Island will be close to normal for temperatures with the Waikato north slightly above normal and the Manawatu and to the south and east near normal to slightly cooler than normal.

Temperature

January

Almost all of the North island should be slightly to moderately above normal

February

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

March

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

Precipitation

December

Northland should be near normal and the Waikato, Bay of Plenty down through Taranaki and Manawatu into Wellington should be slightly drier than normal while the east coast from Gisborne down to the east coast of Wellington should be normal to slightly and in some areas moderately wetter than normal.

January

Northland and East Cape south to Wellington should be near normal with the Waikato, bay of plenty and parts of Taranaki and the Manawatu slightly direr than normal.

February

Near normal across nearly the entire North Island but patches of slightly wetter condition in Northland and East Cape through Hakes Bay.

South Island

Temperature

December

Much of the South Island will be close to normal for temperatures with the West Coast slightly above normal and the Manawatu and to the East Coast slightly cooler than normal.

January

Almost all of the South Island should be slightly to moderately above normal.

February

Almost all of the South Island should be slightly to moderately above normal.

March

Almost all of the South Island should be slightly to moderately above normal.

April

Almost all of the South Island should be slightly to moderately above normal.

May

Almost all of the South Island should be slightly to moderately above normal.

Precipitation

December

Near normal to slightly wetter throughout the region.

January

Near normal in the east and slightly to moderately drier in the west.

February

Near normal in the east and slightly to moderately drier in the west.

March

Slightly to moderately wetter than normal in the east and normal to slightly drier in the west.

April

Slightly to moderately wetter than normal in the east and normal to slightly drier in the west.

May

Near normal throughout the island with slightly wetter conditions in the Southern Canterbury and parts of Otago.

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