Synopsis: A strong El Niño is expected to gradually weaken through spring 2016, and to transition to ENSO-neutral during late spring or early summer. A strong El Niño continued during December, with well above-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean. All weekly Niño indices decreased slightly from the previous month. The subsurface temperatures in the central and eastern Pacific, while still well above average, weakened due to an upwelling equatorial oceanic Kelvin wave. Significant low-level westerly wind anomalies and upper-level easterly wind anomalies continued over much of the tropical Pacific. During the last week, another westerly wind burst occurred in the east-central Pacific. The traditional and equatorial Southern Oscillation Index (SOI) values remained strongly negative. Also, convection remained strong over the central and east-central tropical Pacific, and suppressed over Indonesia. Collectively, these atmospheric and oceanic anomalies reflect the continuation of a strong El Niño episode. Most models indicate that a strong El Niño will weaken with a transition to ENSO-neutral during the late autumn or early winter in the Southern hemisphere. The forecasters are in agreement with the model consensus, though the exact timing of the transition is difficult to predict. A strong El Niño is expected to gradually weaken through autumn 2016, and to transition to ENSO-neutral during late spring or early summer.
Most of the island should be slightly to moderately warmer than normal.
Almost all of the North Island should be slightly above normal.
Slightly to moderately wetter than normal across nearly the entire island with even wetter conditions possible in the far north.
Near normal across nearly the entire island with slightly drier parts in far eastern Northland and East Cape through Hawkes Bay.
Almost all of the South Island should be slightly to moderately above normal.
Almost all of the South Island should be slightly to moderately above normal.
Near normal across the island except the far north that could be moderately wetter than normal.
Most of the island should be near normal.