Synopsis: ENSO-neutral conditions are favored to continue through at least the Southern Hemisphere fall 2017, with increasing chances for El Niño development by late winter and spring.
ENSO-neutral conditions continued during March, with near-average sea surface temperatures (SSTs) across the central equatorial Pacific and above-average SSTs in the eastern Pacific. The latest weekly Niño index values were near zero in the Niño-4 and Niño-3.4 regions, and +0.8 and +0.9°C farther east in the Niño-3 and Niño-1+2 regions, respectively. The upper-ocean heat content anomaly, averaged across the central and eastern Pacific, decreased to near zero during March, a reflection of above-average temperatures at depth in the east offset by below-average temperatures in the central Pacific. Atmospheric convection remained suppressed over the central tropical Pacific and enhanced over the Maritime Continent. The low-level easterly winds were enhanced over the central and western tropical Pacific, and weaker than average over the eastern Pacific. Also, upper-level westerly winds were anomalously easterly over the western and far eastern Pacific, while the Southern Oscillation Index was near average. Overall, the ocean and atmosphere system is consistent with ENSO-neutral conditions.
Most models predict the continuation of ENSO-neutral (3-month average Niño-3.4 index between -0.5°C and 0.5°C) through the late Southern Hemisphere fall (April-June). However, at least one-half of the dynamical model forecasts, including the NCEP CFSv2, anticipate an onset of El Niño as soon as the April-June season. Because of typically lower skill in forecasts made at this time of the year, and the lingering La Niña-like tropical convection and wind patterns over the western half of the Pacific basin, the forecaster consensus favors ENSO-neutral during April-June with a 60-65% chance. Thereafter, there are increasing odds for El Niño toward the second half of 2017 (~50% chance from approximately August-December). In summary, ENSO-neutral conditions are favored to continue through at least the late Southern Hemisphere fall 2017, with increasing chances for El Niño development by late winter and spring.
Almost all of the North Island should be near normal to slightly warmer than normal in the southern half.
Normal across most of the island with perhaps slightly wetter than normal in East Cape and Hawkes Bay.
Some isolate areas should be slightly warmer than normal but most of the island should be near normal.
Slightly drier across the west coast and near normal to moderately wetter than normal along much of the east coast.