The 2015 El Niño continues to strengthen, Australian Bureau of Meteorology (BOM) said in their June 23, 2015 update. International climate models surveyed by BOM indicate further consolidation is likely.
Central and eastern tropical Pacific Ocean sea surface temperature indices are more than 1 °C above average for the sixth consecutive week, the agency said.
El Niño events typically strengthen during the second half of the year, reaching full strength during late spring or early summer (southern hemisphere). However, it is not possible at this stage to determine how strong this El Niño will be.
The SST anomaly map for May 2015 shows positive anomalies across the equatorial Pacific. These positive anomalies extend from the South American coastline, and past the International Date Line to around 160°E. The northeast Pacific Ocean continues to remain above average, while SST anomalies surrounding Australia cooled compared to April, with May anomalies in the Australian region generally close to average.
All five NINO indices averaged over the month were greater than +1 °C, which again has not occurred since the 1997–98 El Niño.
|NINO3||+0.8||+1.2||0.4 °C warmer|
|NINO3.4||+0.8||+1.1||0.3 °C warmer|
Baseline period 1961–1990. Image and data credit: BOM.
The four-month sequence of sub-surface temperature anomalies (to June 22) shows a generally similar pattern has been maintained in June so far as was present for May and April, although the strength of warm anomalies has increased across the three month period.
For June to June 23, warm anomalies are evident across the top 100 m to 200 m of the equatorial Pacific sub-surface between about 160°E and the South American coast. Anomalies across large areas of the eastern half of the equatorial Pacific reached more than +4 °C. Cool anomalies persist in the sub-surface of the western equatorial Pacific.
Image credit: BOM.
The Southern Oscillation Index (SOI) has risen over the past two weeks, although this return to neutral values is expected to be temporary and results from local weather factors rather than a change in the broadscale pattern.
The latest 30-day SOI value to June 21 was +0.7. The 90-day SOI remains within El Niño territory, indicating persistent higher atmospheric pressure in the western Pacific at the three-month timescale.
Image credit: BOM.
Trade winds over the western half of the tropical Pacific were weaker than average for the 5 days ending June 21. Trade winds have been consistently weaker than average, and on occasion reversed in direction, since the start of 2015.
Cloudiness near the Date Line has returned to above-average values during the past two weeks. Cloudiness has been generally above average since the start of March, with brief forays into slightly below average values at the end of May and start of June.
Cloudiness along the equator, near the Date Line, is an important indicator of ENSO conditions, as it typically increases (negative OLR anomalies) near and to the east of the Date Line during El Niño and decreases (positive OLR anomalies) during La Niña.
All eight of the surveyed international climate models indicate the central Pacific Ocean will warm further during the coming months.
All surveyed models indicate that NINO3.4 will remain above El Niño thresholds until at least late 2015.
The Indian Ocean Dipole (IOD) is currently neutral. The latest weekly value of the IOD index to June 21 is −0.07 °C. Temperatures in the Indian Ocean are warmer than average over much of the basin. Three of the five surveyed international climate models indicate a positive IOD event will occur during the southern hemisphere winter or spring.
Data and analysis source: BOM
"2015 El Niño is likely to surpass that experienced in 1997-1998"
The unfolding El Niño event is predicted by climate models to be a major event, possibly one of the strongest ever recorded, UN Office for the Coordination of Humanitarian Affair said today.
What does this mean for the Pacific?
Hight risk of severe drought in PNG, Solomon Islands, Vanuatu, New Caledonia, Fiji, Tonga, Samoa, Niue and Cook Island. The risk of drought is also high for Palau, Northern Marianas and Guam, FSM and Marshall Islands.
Above normal rainfall is expected in Kiribati between June and August 2015
There is an elevated risk of intense cyclones, potentially early start and late nish of the cyclone season, and an elevated likelihood of cyclones particularly in Niue, Samoa and Cook Islands (east of Tonga).
Increased risk of disease by extreme weather events including oods and droughts that can precipitate outbreak of diseases including diarrhoea, leptospirosis and typhoid, by exposure to contaminated water or decreased hygiene due to water shortages; and increased vector borne diseases including dengue, chikungunya and Zika virus due to increase mosquito vectors and increased temperatures that can enhance reproduction and transmission of these viruses.
Image credit: UNOCHA. Click here for PDF version.
Featured image credit: BOM.