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Global setting: July 2019

30 August 2019

During June2019, sea surface temperature anomalies remained above El Niño thresholds (i.e. +0.70 ̊C) in the central Pacific for the fourth consecutive month. The NINO3.4 Index (in the central Pacific) anomaly for June (to the 23rd) was +0.75 ̊C. The NINO 1+2 Index (in the far eastern Pacific) was near normal.

Upper-oceanic heat content anomalies once again increased in the central Pacific (170W-150W) but continued to decrease in the eastern (110W-100W) and western (160E to the Dateline) Pacific. The distribution of ocean heat content across the Pacific reflects ongoing El Niño-Modoki conditions.

The Southern Oscillation Index (SOI) was on the El Niño side of neutral for the second consecutive month (preliminary June value -0.7).

Trade winds were slightly stronger than normal in the western and central Pacific during June. A strong westerly wind event is expected across the central Pacific during late June and early July. Later in July, enhanced trade winds are again expected to develop. Therefore, sea surface temperatures may increase during the first half of July followed by a decrease later in the month.

Model guidance suggests that El Niño conditions will most likely (60% chance) continue over the next three months; however, a gradual weakening of sea surface temperature anomalies is possible in the equatorial Pacific. For the October –December 2019 period, the probability for El Niño continues at 60% before increasing to 65% during January –March 2020.

Sea Surface Temperatures

New Zealand’s coastal water temperatures for June 2019 remain above average for all areas except the east of the North Island. Sea surface temperatures over the Tasman Sea and far Southwest Pacific remain, in general, above average for the time of year with anomalies of around +1.0 ̊ to 1.5 ̊C. Warmer than average seas may help to modify cold air masses that move toward New Zealand from late winter into early spring and contribute to spells of above average temperatures.

Warmer than average sea surface temperatures are forecast to persist during the coming three-month period.

Monthly values of the Southern Oscillation Index (SOI), a measure of changes in atmospheric pressures across the Pacific, and the 3-month mean (black line). SOI mean values: June SOI -0.95; June-August average -0.6.
Differences from average June surface temperatures in the seas around New Zealand

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