ENSO Update

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Bulletin January 2020 - Summary

In the Pacific Ocean, indicators of the El Niño–Southern Oscillation (ENSO) are neutral.

Most climate models indicate ENSO will remain neutral until at least the end of the southern hemisphere autumn, meaning it will have limited influence on the tropical climate.

A pulse of Madden-Julian Oscillation (MJO) is currently active over the Maritime continent. Associated rainfall was evident over the weekend and towards the beginning of week 3 (January).

SPCZ shifted away from Vanuatu and extended over Fiji towards French Polynesia, bisecting through Samoa and Cook Islands. Suppressed rainfall was experienced over most of the islands in December.

Average Sea Surface Temperatures (SSTs) remained warmer than average across much of the western equatorial Pacific Ocean, however SSTs over Vanuatu were mostly normal, with slightly warmer than average over the northern islands.

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Bulletin January 2020 - El Nino Oscillation

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 5 January is −5.7. The 90-day value is also −5.7. The 30-day SOI values have generally remained within neutral bounds over the past month.

Sustained negative values of the SOI below −7 typically indicate El Niño while sustained positive values above +7 typically indicate La Niña. Values between +7 and −7 generally indicate neutral conditions.

While the SOI is an important index that tracks changes in tropical air pressure, we consider a much wider range of atmospheric and oceanic conditions when we assess the status of ENSO. This includes winds, clouds, ocean currents and both surface and sub-surface ocean temperatures, as well as outlooks for the months ahead.

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Bulletin January 2020 - MJO

The Madden-Julian Oscillation (MJO) is a global feature of the tropical atmosphere. It affects the tropical weather on weekly to monthly timescales. The MJO is basically a "pulse" of moving cloud and rainfall that circulates the equator every 30 to 60 days.

Whenever an MJO is active over a particular location, it influences wind, cloudiness and rainfall. During cyclone season, MJO events are more likely to boost the development of Tropical cyclones.

The MJO phase diagram below illustrates the progression of MJO over 4 locations along the equator. Vanuatu is included in the Maritime Continent. When the index (numbered lines) is within the centre circle, the MJO is considered weak. Outside the circle the index is stronger and will move in an anti-clockwise direction.

The MJO is currently active over the Maritime Continent (blue line) and is expected to remain until mid-January before entering the Western Pacific. Vanuatu is to expect showers of rainfall this week, with possibility of Tropical lows developing into Tropical Cyclones.

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Note: Due to frequent images update from source provider, the quoted Sources might not give the same images as shown

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Bulletin January 2020 - Cloud

Global maps of outgoing longwave radiation (OLR) highlight regions experiencing more or less cloudiness. The top panel is the total OLR in Watts per square metre (W/m²) and the bottom panel is the anomaly (current minus the 1979-1998 climate average), in W/m². In the bottom panel, negative values (blue shading) represent above normal cloudiness while positive values (brown shading) represent below normal cloudiness.

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Note: Due to frequent images update from source provider, the quoted Sources might not give the same images as shown

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Bulletin January 2020 - Rainfall

30 day accumulated rainfall (mm):
https://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Figures/curr.p.30day.figa.gif

30 day rainfall anomalies (mm):
https://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Figures/curr.p.30day.figb.gif

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Source

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Source

Note: Due to frequent images update from source provider, the quoted Sources might not give the same images as shown

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Bulletin January 2020 - SST

Image 1: Monthly temperatures

The four-month sequence of equatorial sub-surface temperature anomalies (to January) shows the top 200m of the western to central equatorial Pacific is warmer than average, with cooler than average waters at a depth of around 50 to 200 m in the west. Small volumes of water reach more than 2 degrees warmer/cooler than average in each region respectively.

The pattern has remained somewhat similar over the past three months, with mostly weak to moderate temperature anomalies. The area of cool anomalies below the surface has migrated eastward over those three months.


Image 2: 5-day sub-surface temperatures

For the five days ending 8 January, the sub-surface of the ocean was close to average temperature along the equator. A small band of warmer than average water extends from the Date Line at 150 m depth, across to the shallow eastern Pacific, with the warmest anomalies more than 3 °C warmer than average near the Date Line. A weak pool of cooler water sits around 100 to 200 m depth in the far west.

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Source

Note: Due to frequent images update from source provider, the quoted Sources might not give the same images as shown

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Bulletin January 2020 - MSLP

The December mean sea level pressure (MSLP) anomaly map shows negative anomalies near and east of the Dateline in the equatorial Pacific and northeast of the Cook Islands. The negative anomalies over Fiji are likely to be associated with tropical cyclone Sarai which passed close to Fiji and tropical disturbance 02F which developed close to American Samoa in late December. Positive anomalies were also present east of the Dateline in the south Pacific subtropics. Areas of above (below) average MSLP usually coincide with areas of suppressed (enhanced) convection and rain through the month.

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Source

Note: Due to frequent images update from source provider, the quoted Sources might not give the same images as shown

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Bulletin January 2020 - Model Outlooks

Most international climate models indicate central tropical Pacific sea surface temperatures in the NINO3.4 region will remain at ENSO-neutral levels through the southern hemisphere autumn 2020. One model of eight approaches El Niño thresholds at times, while another exceeds La Niña thresholds in late autumn.

Link: http://www.bom.gov.au/climate/enso/#tabs=Outlooks

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Bulletin January 2020 - SPCZ

30 day accumulated rainfall (mm):
https://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Figures/curr.p.30day.figa.gif

30 day rainfall anomalies (mm):
https://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Figures/curr.p.30day.figb.gif OR http://iridl.ldeo.columbia.edu/maproom/Global/Precipitation/Anomaly.html

The South Pacific Convergence Zone (SPCZ) shifted southeast further away from the Maritime continent during the previous month, resulted in suppressed rainfall through out most of the stations in Vanuatu. The SPCZ extends southeast bisecting Fiji and Samoa and extending towards French Polynesia.

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