El Niño Weakens, Neutral Conditions Most Likely
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PNG NATIONAL WEATHER SERVICE Seasonal Climate Outlook (May-Jul 2016) Volume 5, Issue 5 12 Apr 2016 El Niño Weakens, Neutral Conditions Most Likely A transition to a ENSO-neutral condition is mostly likely for the May-June-July 2016 forecast period. Even though most of the indicators in the oceans and the atmosphere are all showing signs of the El Niño weakening to a weak or moderate levels, the sea surface temperatures continue to be at El Niño level hence the effects of El Niño will continue for sometime yet. The Southern Oscillation Index (SOI) continues to remain negative, well below the El Niño threshold whilst the Trade winds are also weaker. International climate models suggests El Niño will continue to weaken during the southern autumn, returning to neutral levels by mid-2016. Although the El Niño is weakening, the effects will still be visible especially in the day time temperatures (maximum) and night time temperatures (minimum) giving rise to both hot days and warm nights, especially for maritime provinces. Based on the past El Niño events since 1900, around 50% have been followed by a neutral year, while 40% have been followed by a La Niña event. The likelihood for a La Niña event happening during the second half of this year has increased to 50%. Due to the low skill level in the forecasts of the climate models at this time of the year, it may be a bit too early to pre-empt things here. Hence, we shall be closely monitoring the situation and developments closely over the coming months and advise accordingly should the need to do so arises. Mean Monthly NINO3.4 Forecast (POAMA) Figure 1 below shows the POAMA monthly mean Nino 3.4 forecast commencing on 10 April 2016. The forecast is predicting for a return to neutral conditions towards the second half of this year. The warming trend for El Niño is +0.8 or above and the cooling trend for La Niña is –0.8 or below as illustrated in the figure below. P a g e 2 Seasonal Climate Outlook (May- J u l 2 0 1 6 ) Volume 5, Issue 5 Papua New Guinea Satellite Rainfall Monitoring Figure A shows the satellite based rainfall estimate for the last 30 days from 04 Mar to 02 Apr 2016. Figure B shows the climatology or the normal rainfall amounts expected at this time of the year, i.e. from 04 Mar to 02 Apr 2016. Figure C shows the percentage of normal rainfall as a percentage for the last 30 days from 04 Mar to 02 Apr 2016. The satellite observed rainfall maps shows that the interior Highlands, all of the Western and Oro Province, Figure A and much of the New Guinea Islands been blessed with very good rains. Unfortunately, for other parts of the New Guinea Islands and Central and Gulf Provinces are still relatively 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 interesting to note firstly that the locations receiving rainfall as noted above are doing very well compared to climatology. The rest of the country such as the Central and Gulf provinces, Milne Bay and parts of the New Guinea Islands continues to be in drought Figure B like situation. This is reflected very well in Figure C. Figure C Seasonal Climate Outlook (May- J u l 2 0 1 6 ) Volume 5, Issue 5 P a g e 3 Country Situation The monthly rainfall for the country is as Station Jan 16 Feb 16 Mar 16 shown in Table 1 below. Madang 325.2 252.3 319.0 The highest rainfall for the month of March was recorded at Momote (414.6mm) Momote 308.0 202.0 414.6 and the lowest rainfall was recorded at Wewak (38.8mm). Kavieng 312.6 295.2 346.0 The month of March is the wettest months Nadzab 169.2 207.2 109.4 for the country and it is no surprise to see all the locations in the country receiving Tokua 318.4 205.8 261.4 rainfall in the higher categories except for Wewak which received its lowest rainfall Aiyura 186.0 301.1 274.9 for March since record began. Misima 74.6 116.0 186.2 The location specific predictions from Port Moresby 42.6 228.0 120.6 SCOPIC model are as depicted in Table 2 below together with their forecast for the Wewak 62.4 111.0 38.8 coming 3 months. Vanimo - 225.4 360.0 Rainfall Outlook (May-Jul 2016) Station Median Rainfall (mm) Probability of Exceeding Rainfall Outlook Confidence in Forecast Median Rainfall (%) Madang 754.4 3 Below Normal Very High Confidence Momote 895.0 21 Below Normal Good Confidence Kavieng 725.2 34 Below Normal Very Low Confidence Nadzab 292.6 37 Below Normal Very Low Confidence Tokua 647.9 44 Below Normal Very Low Confidence Aiyura 317.0 29 Below Normal Low Confidence Misima 625.2 5 Below Normal Very High Confidence Port Moresby 118.1 47 Below Normal Low Confidence Wewak 629.8 24 Below Normal Low Confidence Vanimo 649.5 59 Above Normal Very Low Confidence Goroka 240.8 5 Below Normal Very High Confidence How to interpret Table 2 Take for instance Madang From Table 2, the median rainfall is 754.4mm. The probability of exceeding this rainfall from SCOPIC model is only 3% whilst the probability of not exceeding is 97%. Hence, the chances of exceeding the median rainfall is lower therefore the expected rainfall outlook is Below Normal rainfall with very high 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 May to July 2016. The country continue to be replenished with much needed rainfall after the prolonged drought last year. Despite this, the long term scenario is still indicating drought like conditions across certain 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. Likewise, Port Moresby and Wewak, are experiencing severe shortage of water problems ranked 3rd and 4th respectively since November and May last year. 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). .