Island Climate Update

The NINO3.4 Index anomaly (in the central Pacific) for the last month (through the 3 rd of January) was 0.84˚C, increasing from 1.03˚C from last month. This likely means that the oceanic La Niña has peaked however, La Niña’s influence on the atmosphere is expected to last for months to come.

During November, the NINO3.4 Index anomaly (central Pacific) was 1.02˚C. The NINO 1+2 Index (eastern Pacific) was 0.54 C. The most unusually cool SSTs have now shifted into the central Pacific.

During October, the NINO3.4 Index anomaly (central Pacific) was 0.86˚C. The NINO 1+2 Index (eastern Pacific) was 0.56 C. Upper oceanic heat content continued to decrease in the east central part of the Pacific basin. Heat content continued to be higher than normal in the western Pacific. Overall, the pattern is consistent with La Niña conditions.

During September, the NINO3.4 Index anomaly (central Pacific) was 0.71˚C. The NINO 1+2 Index (eastern Pacific) was 0.76 C. Upper oceanic heat content remained lower than normal with continued decreases observed in the east central part of the Pacific basin since August. Heat content continued to be higher than normal in the western Pacific. Overall, the pattern is consistent with La Niña conditions.

During August, the NINO3.4 Index anomaly (in the central Pacific) was 0.42˚ C. The NINO 1+2 Index (eastern Pacific) was 0.85 C. Upper oceanic heat content remained lower than normal in the eastern and central equatorial Pacific with a substantial decrease observed in the east central part of the basin. Overall , the pattern is well aligned with a developing La Niña event.

During July, the NINO3.4 Index anomaly (in the central Pacific) was +0.04˚C. The NINO 1+2 Index (eastern Pacific) was 0.72 C, decreasing from 0.57 C in June.

During June, the NINO3.4 Index anomaly (in the central Pacific) was 0.12˚C. Upper oceanic heat content decreased notably across the east central equatorial Pacific.

During May the NINO3.4 Index anomaly (in the central Pacific) for May was +0.01˚C, with upper oceanic heat content continuing to decrease across the equatorial Pacific.

Trade winds during April were slightly stronger than normal along the equator. This pattern is expected to continue over the next 1 2 months, most likely leading to continued cooling in the west central Pacific.

El Nino –Southern Oscillation (ENSO) neutral conditions continued during December 2019. Both the Southern Oscillation Index (SOI) and sea surface temperatures (SSTs) remained on the El Niño side of neutral but weakened compared to previous months.

ENSO-neutral conditions continued during November 2019, although the Southern Oscillation Index (SOI) dipped into El Niño territory and sea surface temperatures (SSTs) were on the El Niño side of neutral.

ENSO-neutral conditions continued during October 2019, although the Southern Oscillation Index (SOI) and sea surface temperatures (SSTs) were on the El Niño side of neutral.

Upper-oceanic heat content anomalies continued to decrease in the eastern and east-central equatorial Pacific during September. The core of the warm pool that had been associated with a central Pacific El Niño earlier in the year was located just west of the International Dateline.

Upper-oceanic heat content anomalies continued to decrease, but remained slightly above average in the west-central equatorial Pacific.

During July 2019, SSTs dipped below El Niño thresholds in the central Pacific for the first time in 5 months.

During June 2019, the atmosphere continued to respond to a warm pool of water in the central and western Pacific, with above normal rainfall and cloud centred along and just west of the International Dateline.

During May 2019, the atmosphere continued to respond to a warm pool of water in the central and western Pacific.

During April 2019, the atmosphere once again responded to a warm pool of water in the central and western Pacific, withabove normal rainfall and cloud centred along and just west of the International Dateline

Warmer than average sea surface temperatures (SSTs) now cover the tropical Pacific uniformly, a sign of a strengthening oceanic El Niño event.

Over the past month, Sea surface temperatures (SSTs) remained above average in the equatorial Pacific Ocean, particularly near and just west of the International Dateline. The NINO3.4 index SST anomalies however remained just below +0.5 ̊C during February 2019.

Over the past month, sea surface temperatures (SSTs) in the central Pacific have remained above normal particularly near and west of the International Dateline, although declined slightly below the conventional threshold for El Niño.