PNG NATIONAL WEATHER SERVICE Seasonal Climate Outlook (Mar-May 2016)

Volume 5, Issue 3 23 Feb 2016 Strongest El Niño continues to Weaken

The strongest El Niño on record continues to weaken after causing six months of havoc in the country. All the indicators in the oceans and the atmosphere are all showing signs of declining. Sea surface temperatures (SST) are cooler than normal in the Tropical Pacific whilst the Southern Oscillation Index (SOI) continues to fall below the El Niño threshold. The International Climate models are all predicting for a return to ENSO-neutral conditions towards the second half of this year. Thanks to the monsoonal rains, much of the country is slowly recovering from the drought except for some parts of the Western Province which continue to experience drier conditions. Even though, the country is experiencing good rains, it is still premature to suggest that the drought is over. The country was starved of rainfall for the past 6 months causing severe droughts across the country and it is only sensible to suggest that the country is still in its recovery stage. It will require some more time to return to normal. This return to normal situation is dependent on how much good rains the country is expected to receive from the remaining 2 months of the monsoon season. Come May, the country heads into its dry season proper and the chances are that the country may head back into more drier conditions. However, based on the past El Niño events since 1900, around 50% have been followed by a neutral year, while 40% have been followed by La Niña. Even though, our forecast is leaning towards a neutral year, for the second half of 2016, the chances of a La Niña event happening are equally likely.

Mean Monthly NINO3.4 Forecast (POAMA)

Figure 1 below shows the POAMA monthly mean Nino 3.4 forecast commencing on 14 February 2016. The warming trend for El Niño is +0.8 or above and the cooling trend for La Niña is –0.8 or below. The forecast is predicting a return to neutral conditions towards the second half of this year. P a g e 2 Seasonal Climate Outlook (Mar- M ay 2 0 1 6 ) Volume 5, Issue 3

Papua Satellite Rainfall Monitoring

Figure A shows the satellite based rainfall estimate for the last 30 days from 26 January to 24 February 2016. Figure B shows the climatology or the normal rainfall amounts expected at this time of the year, i.e. from 26 January to 24 February 2016. Figure C shows the percentage of normal rainfall or the difference in rainfall from the observed from the normal as a percentage for the last 30 days from 26 January to 24 February 2016. Figure A The satellite observed rainfall maps shows that the highlands, parts of Western Province especially and Oro Province have been receiving very heavy rainfall for the past weeks. This heavy rainfall have been responsible for the landslides in the highlands (Chimbu) and flooding in Oro Province. Port Mo- resby, on the other hand is still dry. By comparing the observed rainfall amounts (Figure A) with the normal rainfall that the country is supposed to receive at this time of the year (Figure B), it is very clear that despite the falls, the vast parts of the Western Province, Central and Figure B and the New Guinea Is- lands continues to be in drought like situation. This is reflected very well in Figure C.

Figure C Seasonal Climate Outlook (Mar- M ay 2 0 1 6 ) Volume 5, Issue 3 P a g e 3

Country Situation

The monthly rainfall for the country is as Station Nov 15 Dec 15 Jan 16 shown in Table 1 below. 126.8 108.0 246.0 The highest rainfall for the month of January was recorded at Tokua (318.4mm) Momote 151.4 270.0 308.0 and the lowest rainfall was recorded at (42.6mm). 287.8 255.4 312.6

Momote, Kavieng and Tokua in the New Nadzab 160.6 280.0 169.2 Guinea Islands continue to receive very good rains which is a welcoming news for Tokua 144.2 - 318.4 our people on the ground. Aiyura 122.7 203.6 186.0 The forecast for the coming 3 months is as Misima 151.4 - 74.6 shown in Table 2 below. Port Moresby 2.4 82.3 42.6

Wewak 66.4 121.6 62.4

Vanimo - 294.8 - Rainfall Outlook (Mar-May 2016)

The location specific predictions from the SCOPIC model are as depicted in Table 2 below. Station Median Rainfall (mm) Probability of Exceeding Rainfall Outlook Confidence in Forecast Median Rainfall (%)

Goroka 560.8 56 Above Normal Very Low Confidence

Momote 828.9 39 Below Normal Very Low Confidence

Kavieng 831.6 62 Above Normal Very Low Confidence

Nadzab 386.0 49 Below Normal Very Low Confidence

Tokua 617.9 93 Above Normal Very High Confidence

Aiyura 590.8 54 Above Normal Very Low Confidence

Misima 801.9 3 Below Normal Very High Confidence

Port Moresby 373.2 15 Below Normal High Confidence

Wewak 604.1 39 Below Normal Very Low Confidence

Vanimo 815.0 46 Below Normal Very Low Confidence

How to interpret Table 2 Take for instance Goroka From Table 2, the median rainfall is 560.8mm. The probability of exceeding this rainfall from SCOPIC model is 56% whilst the probability of not exceeding is 44%. Hence, the chances of exceeding the median rainfall is higher therefore the expected rainfall outlook is Above Normal rainfall with very low confidence in the skill of this forecast at this time of the year. For further information please contact:

The Assistant Director Climate & Special Services PNG National Weather Service P. O. Box 1240 Boroko, NCD.

Telephone: (675) 325 5925 Fax: (675) 325 5544 Email: [email protected]

The Director PNG National Weather Service P. O. Box 1240 Boroko, NCD.

Telephone: (675) 311 2385 Fax: (675) 325 5544 Email: [email protected]

The Drought definition employed here is adopted from SCOPIC which utilizes the 6 month aggregate drought index using Standardized Precipitation Index (SPI) method for the period March to May 2016. The recent down pours have provided short term relief to the country. The long term scenario is still indicating drought like conditions across most parts of the country. Momote and Kavieng, for instance, are still suffering from a severe drought, ranked 2nd and 4th respectively on the severity scale which commenced in June 2015. Port Moresby, Nadzab and Wewak, Goroka and Aiyura, on the other hand are also in drought but with a much lesser severity classification of drought. Please note here that drought is only declared when rainfall is below the 10th percentile (i.e., within the driest 10% of all previous 6 months rainfall totals).