ENSO Update

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Bulletin March 2020 - Summary

31st March 2020 Update:

ENSO remains Neutral for the whole Pacific. There is no El Nino, or La Nina. Neutral will likely remain through June-August.

MJO will be active from the 26th of March 2020, towards the first week of April.

Cloudiness was below normal over Vanuatu for the last 30days ending 7th March.

Rainfall has been near-normal in February 2020. For the next three months (Apr - Jun), expect above-normal rainfall over Torba and Penama, Northeast of Santo and North of Ambrym, with normal rainfall elsewhere.

Sea surface temperatures have been near-normal over Vanuatu in February 2020.

MSLP for March 2020 is normal.

SPCZ shifted east away from Vanuatu in the previous month.

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Bulletin March 2020 - El Nino Oscillation

Latest ENSO update: ENSO remains Neutral for the whole Pacific.

El Niño Southern Oscillation (ENSO) is a single climate feature that has three states: El Niño, La Niña, and Neutral.

During an El Niño, ocean surface tends to warm in the CENTRAL and EASTERN tropical Pacific Ocean. Countries in this region would receive extreme rainfall, while countries in the western tropical Pacific (like Vanuatu) would experience extreme dry conditions.

During a La Niña, ocean surface tends to warm in the CENTRAL and WESTERN tropical Pacific Ocean. Countries in this region (like Vanuatu) would receive extreme rainfall, while countries in the eastern tropical Pacific would experience extreme dry conditions.

During a Neutral phase, ENSO indicators are generally normal. Neither an El Niño or La Niña is active.

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Bulletin March 2020 - MJO

17th March 2020, MJO Update:
MJO was active over the Maritime Continent on the 4th to 10th of March. MJO is expected to be active again from the 26th of March over the Maritime Continent. Associated rainfall from this MJO would be experienced over Vanuatu from the 26th of March, towards the first week of April.

What is an MJO (Madden-Julian Oscillation)?
An MJO is a group of cloud and rain that circulates the globe near the equator, and usually occurs every 30-60 days. When an MJO passes over an area, it brings heavy rain with varying wind speed. During cyclone season, an MJO can help develop tropical cyclones by fueling any overlying low pressure systems.

The diagram below shows the track of the MJO for the past 40 days (coloured lines). [Click to enlarge the diagram]. When the lines are within the circle, MJO is weak and has no influence on rainfall. Outside the circle, the MJO is active and will usually move in an anti-clockwise direction. Vanuatu will most likely experience related rainfall from an MJO event when it moves over the Maritime Continent on the diagram.

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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 March 2020 - Cloud

17th March 2020, Cloud Update:
Cloudiness for the 30 days ending in 7 March was below normal over Vanuatu, indicating suppressed conditions over the country for the past 30 days.

The above maps show regions experiencing more or less cloudiness. The top map is the total outgoing long-wave radiation (OLR), and the bottom map is the cloud anomaly. Outgoing longwave radiation (OLR) is often used as a way to identify tall, thick, convective rain clouds. This means, a region which experiences lower outgoing radiation is an indication of more cloudiness over the area.

The purple shading indicates higher than normal, active or enhanced tropical weather (above normal cloudiness), while brown shading indicates lower than normal cloud or suppressed conditions.

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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 March 2020 - Rainfall

Rainfall for February 2020:
Rainfall has been generally near-normal over the country in the previous month. For specific stations within the country, rainfall has been below-normal at Sola, Bauerfield & Port Vila, and above-normal at Pekoa, Lamap, White-grass and Aneityum.

3-month Rainfall Outlook; April - June 2020:
"General forecast over the country"; expect above-normal rainfall over Torba and Penama, Northeast of Santo and North of Ambrym, with normal rainfall elsewhere.
"Specific forecast for 7 main stations"; expect below-normal to normal rainfall at Sola and Bauerfield, and below-normal rainfall at Pekoa, Lamap, Port Vila, Whitegrass and Aneityum.

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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 March 2020 - SST

17th March 2020, Sea Surface Temperature Update:
Sea surface temperatures have been near-normal over Vanuatu in February 2020.

Top Image: Monthly Sub-surface Temperatures.
This diagram shows temperatures below the sea surface along the equator. During an El Nino, extreme warming of sub-surface temperatures will be evident in the eastern Pacific (RED color will shift and intensify towards the right side of the diagram). While during a La Nina, extreme cooling of sub-surface temperatures will be evident in the eastern Pacific (BLUE color will shift and intensify towards the right side of the diagram). Sub-surface temperatures for March 2020 indicate an ENSO-neutral phase (No El Nino or La Nina).

Bottom Image: Weekly Sub-surface Temperatures.
This diagram shows sub-surface temperatures on a weekly basis. For the week ending on 8th March 2020 (refer to last diagram), only a small region reached more than three degrees warmer than average. Elsewhere, temperatures were generally close to average.

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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 March 2020 - MSLP

17th March 2020, Mean Sea Level Pressure Update:
The March MSLP anomaly map shows atmospheric pressure over Vanuatu was normal over Vanuatu; -1 to 0 over the northern region, and 0 to +1 over the southern region.

Regions of HIGH pressure anomalies (brown shades) are associated with lower rainfall, while higher rainfall are associated with regions of LOW pressure anomalies (purple shades).

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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 March 2020 - Model Outlooks

Six of the eight international climate models surveyed by the Bureau indicate central tropical Pacific sea surface temperatures in the NINO3.4 region will remain at ENSO-neutral levels through the southern hemisphere winter. The remaining two models exceed the La Niña threshold during winter.

ENSO predictions made during autumn tend to have lower accuracy than predictions made at other times of the year. This means that current ENSO forecasts beyond May should be used with some caution.

ENSO events, that is, either El Niño or La Niña, typically begin to develop during autumn, before strengthening in winter/spring. The Bureau will continue to closely monitor the potential for either to develop this year.

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Bulletin March 2020 - SPCZ

A broad convective region was centred on or just north of the equator, with the strongest intensity near 170°E (A). The ITCZ extended eastwards out from this convective region across the northern tropical Pacific (B), while the SPCZ extended southeastward towards Samoa and the southern Cooks. The SPCZ looks to be east of its normal location.

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