Vanuatu Monthly Climate Summary Issued Jan 16 Vanuatu Meteorology and Geo-Hazards

VANUATU MONTHLY CLIMATE SUMMARY ISSUED JAN 16 VANUATU METEOROLOGY AND GEO-HAZARDS

DEPARTMENT Vanuatu Monthly Climate Summary: December 2015 El Niño Southern Oscillation Status  Strong El Niño conditions continued in December 2015.  A number of El Niño-Southern Oscillation (ENSO) indicators suggest that the 2015-16 El Niño peaked during the month of December 2015. Tropical Pacific Ocean temperatures suggest this event is one of the top three strongest El Niño events of the past 50 years.  Strong El Niño continues to dominate the climate of most countries within the Pacific Ocean. Significant Climate Drivers: El Niño Southern Oscillation (ENSO), South Pacific Convergence Zone (SPCZ), Madden Julien Oscillation (MJO), Intertropical Convergence Zone (ITCZ).

 El Niño conditions continued to persist during the month.  The South Pacific Convergence Zone (SPCZ) was displaced northeast of its normal position, bringing higher than normal rainfall totals for the region from the Solomon Islands eastward. The Inter-Tropical Convergence Zone (ITCZ) was displaced southward of its normal position, suppressing rainfall in parts of the north Pacific.  A moderate to strong Madden-Julian Oscillation (MJO) event entered the western Pacific in the last week of December, disrupting the dry conditions associated with the displacement of the SPCZ. Convection was enhanced which increased the chances of Tropical Cyclone in the southwest Pacific. The MJO also brought the rainfall Vanuatu experienced in the last week of December.  Tropical cyclone Ula, the second cyclone of the season, formed in late December and impacted the southern islands of Vanuatu in early January 2016.

ITCZ

SPCZ

[Source: www.niwa.co.nz/climate/icu ]

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VANUATU MONTHLY CLIMATE SUMMARY ISSUED JAN 16 VANUATU METEOROLOGY AND GEO-HAZARDS

DEPARTMENT Significant Weather events: Tropical Cyclones, Trough/Lows & High Pressure systems  Tropical Cyclone Ula – started developing in the last week of December 2015 and entered the Vanuatu waters during early January 2016. Rainfall performance  The average Total Rainfall Measuring Mission (TRMM) rainfall for the month of December (map below) shows Vanuatu receiving below 10mm rainfall per day . December synoptic station records showed that rainfall was normal for Sola, Pekoa and Bauerfield and above normal for Lamap, Port Vila, Whitegrass and Aneityum. The graph below shows the rainfall recorded at each station for the month compared to the long term average rainfall for the month of December at each station. Despite the

December 2015 rainfall vs December long term average 500 400 300 200

Rainfall ( ml) Rainfall 100 Dec 2015 0 Dec long term average rainfall

Stations

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VANUATU MONTHLY CLIMATE SUMMARY ISSUED JAN 16 VANUATU METEOROLOGY AND GEO-HAZARDS

ongoing El Niño, rainfall was DEPARTMENT high all throughout because of the MJO event that occurred during the last week of December.

Selected Vanuatu Rainfall Network ( VRN) sites recorded Rainfall for the month of December are displayed above. Temperature and Atmospheric Pressure  The regional atmospheric circulation pattern for December 2015 was characterised by low pressure anomalies to the east of New Zealand and over Samoa, the Cook Islands, and French Polynesia. High pressure anomalies were present over the Tasman Sea, the Coral Sea, the Solomon Islands and Papua New Guinea. This atmospheric circulation pattern produced anomalous southerly flow across many islands south of 10°S including Vanuatu. Westerly anomalies dominated the western Equatorial Pacific, consistent with strong El Niño conditions..  Vanuatu also experienced pressure anomalies that were slightly higher than normal geopotential height (+10) during the month as showing in the map below.

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VANUATU MONTHLY CLIMATE SUMMARY ISSUED JAN 16 VANUATU METEOROLOGY AND GEO-HAZARDS

Sea level Pressure DEPARTMENT The December Mean Sea Level Pressure (MSLP) anomaly map below shows positive anomalies greater than +1 hPa over the western tropical and subtropical south Pacific to the west of the Solomon Islands, exceeding +2 hPa over northeast Australia and to the south of New Caledonia. These MSLP anomaly patterns are typical for El Niño, with negative MSLP anomalies being associated with enhanced convection close to the equator in the central and eastern Pacific. Areas of above (right) average MSLP usually coincide with areas of suppressed (enhanced) convection and rain throughout the month. Vanuatu was within the above average MSLP during the month of December.

Wind  The trade winds were slightly stronger than normal in the central and west Pacific, and slightly weaker than normal in the eastern Pacific, but remain within the normal range. As shown in the map below there were higher than normal westerly wind anomalies over the country towards the end of December which are consistent with the current El Niño.

Call: (+678) 23866, Email: [email protected], Visit: www.meteo.gov.vu

VANUATU MONTHLY CLIMATE SUMMARY ISSUED JAN 16 VANUATU METEOROLOGY AND GEO-HAZARDS

[source: http://www.bom.gov.au/climate/mjo/#tabs=TimeDEPARTMENT -longitude ] Sea Surface Temperatures (SST)  December sea surface temperature (SST) anomalies were greater than +2.0 °C in the equatorial Pacific between the Date Line and South America.  Above normal sea surface temperatures remained strong along the Equator, around south-eastern Australia and the Tasman Sea, and also around Vanuatu and south of French Polynesia. Negative sea surface temperature anomalies strengthened to the east of New Zealand and southeast of Fiji.

[Source: http://www.niwa.co.nz/climate/icu/island-climate-update-184-january-2016/el- ni%C3%B1osouthern-oscillation-enso ] Sea level  Positive sea level anomalies persist in the central and eastern equatorial Pacific. East of 160°W these anomalies exceed +24 cm. As shown in the graphs below sea level records (high tide and low tides) for the month of December were higher at Port Vila compared to Luganville meaning norther region of Vanuatu will experience lower sea level thank southern region

[source : http://www.ioc-sealevelmonitoring.org/station.php?code=luga ]

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VANUATU MONTHLY CLIMATE SUMMARY ISSUED JAN 16 VANUATU METEOROLOGY AND GEO-HAZARDS

Coral Reef DEPARTMENT  Coral bleaching alerts were current for most of the central equatorial Pacific in December. Models had shown bleaching warnings for Vanuatu. Summary December’s atmospheric and ocean conditions reflected the ongoing El Niño event. Atmospheric pressures, SST and wind anomalies were slightly higher than normal in December. The El Niño -typical ongoing shift of the SPCZ to the northeast meant that supressed rainfall over Vanuatu was expected, but the presence of the MJO brought average and above average rainfall to the country. The dominant climate drivers for the month of December were El Niño and MJO.

Call: (+678) 23866, Email: [email protected], Visit: www.meteo.gov.vu