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Island Climate Update 260 - May 2022

The NINO3.4 Index anomaly over the last month (to 1 May) was -0.66˚C, an increase compared to the previous month but still near the La Niña threshold. The April monthly SOI was +2.1, well within the La Niña range and the 3rd highest April value on record since at least 1876 (only April 2011 and  April 1904 were higher); this suggests that the atmospheric imprint of La Niña is strong.

Upper-oceanic heat content (OHC) continued to decrease. Below normal OHC was present in the central and eastern Pacific and above normal west of the International Date Line. This pattern was consistent with continued La Niña conditions.

In the subsurface equatorial Pacific, a narrow layer of above average waters was present just below the surface in the eastern Pacific. If this were to surface over the next month, it could lead to warming conditions in the NINO 1 and 2 regions. In the western Pacific, a warm pool of water intensified at depth (below 100 m). The potential eastward progression of this warm pool will be monitored in the coming months.

La Niña conditions are forecast to continue during May-July (60% chance). Between August- October, La Niña and ENSO neutral conditions are about equally likely (45-50% chance). During November-January, La Niña is favoured at around 50%.

The 2021-22 Southwest Pacific tropical cyclone (TC) season has ended. There were 7 TCs in total, slightly fewer than normal. A pulse of the Madden-Julian Oscillation developing in the Indian Ocean is forecast to move across the Pacific in mid-May; although TC season has ended, remain vigilant.