3rd Quarter, 2016 Vol. 22, No. 3 ISSUED: August 23rd, 2016 Providing Information on Climate Variability in the U.S.-Affiliated Pacific Islands for the Past 20 Years. http://www.weather.gov/peac CURRENT CONDITIONS The epic El Niño of 2015/16 is now in its post-Peak phase (Fig. In response to the impact of drought conditions on water sup- 1) with the CPC’s Oceanic Niño Index poised to soon transform ply, local governments issued proclamations concerning from El Niño to ENSO-neutral (Fig. 2). Indeed, taking a wide drought: the governments of Palau and of the FSM declared view of the recent behavior of the Pacific climate, the CPC, on its drought emergencies for portions of their jurisdictions, and the 14 July diagnostic discussion, officially announced the transition government of the Republic of the Marshall Islands went even of the state of the Pacific climate system from El Niño to ENSO- further with a declaration of drought disaster. With very dry neutral. During the first half of 2016, very dry conditions pre- conditions now abating at most locations, all emergency water vailed across Micronesia and into Hawaii, with all of the report- use directives and outdoor fire restrictions have been lifted. ing locations within Micronesia receiving below average rainfall Information about the nature and extent of drought impacts is (Figs 3 and 4). Several records for low rainfall were set still being gathered and assessed. During June 2016, Universi- (repeated for emphasis from the 2Q Newsletter): ty of Guam (UOG) PEAC scientists completed drought assess- ment trips to Saipan and to Yap, and will soon travel to (1) Koror, Palau — driest Oct-Mar, driest Apr-Mar; Chuuk, Pohnpei and Kosrae to assess the impact of the 2015 (2) Yap Island — driest Oct-Mar; El Niño in these locations. The PEAC continues to be actively (3) Pohnpei Island — 3rd driest Oct-Mar, 4th driest Apr-Mar; involved in cataloging and assigning drought impacts to the (4) Nukuoro (Pohnpei State) — driest Apr-Mar, 3rd driest Oct-Mar; (5) Ulithi (Yap State) — 2nd driest Oct-Mar, driest March; drought categories (D0, D1, D2, D3 and D4) used in the U.S. (6) Woleai (Yap State) — driest Oct-Mar, driest Apr-Mar; National Drought Monitor to portray the severity of drought. (7) Alingalapalap (RMI) — 2nd driest Oct-Mar; In an ongoing project to incorporate the US-API into the (8) Kwajalein (RMI) — 5th driest Oct-Mar; USDM, the PEAC is working closely with Mr. Richard Heim (9) Majuro (RMI) — driest Oct-Mar; (co-author of the weekly USDM) and the Guam Weather Fore- (10) Jaluit (RMI) — driest Oct-Mar, driest Apr-Mar; cast Office and other regional Weather Service Offices. (11) Mili (RMI) — 2nd driest Oct-Mar, driest March. 80 2016 1st Half (JFMAMJ) Rainfall (Inches) 70 60 50 40 30 RAINFALL (INCHES) 20 10 0 Mili Ulithi Rota Koror Tinian Palikir Wotje Utirik Woleai Fananu Kosrae Nukuoro Yap WSO Lukunoch Kwajalein Pago Pago Guam WFO Palau Airport Saipan C. H. Guam AAFBChuuk WSO Majuro WSO Saipan Airport Pohnpei WSO Kapingamarangi Figure 3. 2016 First Half rainfall amounts in inches. Figure 1. Typical evolution of the Niño 3.4 ENSO index following a 150 2016 1st Half (JFMAMJ) Rainfall strong El Niño event, with timing of “post-Peak” and subsequent phases Percent of Average indicated. 125 100 75 50 PERCENT OF AVERAGE PERCENT 25 0 Mili Ulithi Rota Koror Tinian Palikir Wotje Utirik Woleai Fananu Kosrae Nukuoro Yap WSO Lukunoch Kwajalein Pago Pago Guam WFO Palau Airport Saipan C. H. Guam AAFBChuuk WSO Majuro WSO Saipan Airport Pohnpei WSO Kapingamarangi Figure 2. The NCEP Oceanic Niño Index (ONI) for the period 1996 Figure 4. 2016 First Half rainfall as a percent of average . through the value plotted for AMJ 2016. Page 2 Pacific ENSO Update CURRENT CONDITIONS Sea Level : After nearly a decade of very high values, the sea Synopsis: La Niña is slightly favored to develop during Au- level dramatically lowered across Micronesia during 2014 and gust - October 2016, with about a 55-60% chance of La Niña 2015 (Fig. 5; also see sea level section). Since the middle of during the fall and winter 2016-17. 2013 to the end of 2015, the total drop in the sea level at both Guam and at Kwajalein was approximately 40 cm, or 1.3 feet! A sharp drop of mean sea level typically occurs during El Ni- “ENSO-neutral conditions were observed during the past month, ño, with the lowest value of sea level occurring in December of the El Niño year. A sharp rise of sea level typically occurs featuring slightly below average sea surface temperatures in the first few months of the post-Peak year of an El Niño (SSTs) close to the equator across the eastern tropical Pacific event. By February 2016, the sea level across Micronesia saw Ocean (Fig. 6). While the weekly Niño-1+2 and Niño-4 regions a sharp reversal of its prior steep downward trend to begin the were near average, the Niño-3 and Niño-3.4 indices were slight- anticipated steady rise of sea level for the rest of 2016. See ly below average (approaching -0.5°C) during July. Although the sea level discussion for more details and specific forecasts. below-average subsurface temperatures continued, they weak- ened during the past month but remained near the surface in parts of the central and eastern equatorial Pacific. Atmospheric anomalies over the tropical Pacific Ocean also indicated ENSO- neutral conditions. Both the traditional Southern Oscillation index and the equatorial Southern Oscillation index were near average during July, while the upper and lower-level winds also were near average across most of the tropical Pacific. Convec- tion was suppressed over portions of the western and central tropical Pacific and enhanced over part of Indonesia. Overall, the combined ocean and atmosphere system is reflective of EN- SO-neutral.” “Many models favor La Niña (3-month average Niño-3.4 index less than or equal to -0.5°C) by the beginning of the Northern Hemisphere fall, continuing into winter. Statistical models pre- Figure 5. Time series of sea level at Guam and Kwajalein from dict a slightly later onset time (i.e., mid- to late fall) than dynam- January 2012 through May 2016. Note the steady decline that reach- ical models, and also predict a slightly weaker event. The fore- es a low point at the end of 2015. This is consistent with El Niño caster consensus favors La Niña onset during the August- reaching its peak in late 2015. Note also the abrupt upturn in early October season, and predicts a weak event (Niño-3.4 index be- 2016 (within the red oval). This is consistent with the decay of El tween -0.5°C and -1.0°C) if La Niña forms. Overall, La Niña is Niño. slightly favored to develop during August - October 2016, with about a 55-60% chance of La Niña during the fall and winter CURRENT STATE OF ENSO 2016-17. ... ”. Climate Prediction Center National Centers for Environmen- Current Situation and Outlook Summary tal Prediction. NOAA/National Weather Service. College Park, MD 20740 ENSO-neutral conditions have persisted since the end of the strong El Niño in May. The majority of the models surveyed and expert opinion suggest La Niña development is possible in the third quarter of 2016, with about a 50-65% probability, lasting through the remainder of 2016. The most likely strength of a La Niña, should it develop, is weak. There is virtually no chance of El Niño re-development in 2016. Figure 6. Average sea surface temperature (SST) anomalies (°C) for the Pacific ENSO Update is Now Available Online: week centered on 4 May 2016. Anomalies are computed with To receive notification when the newsletter is available online respect to the 1981-2010 base period weekly means. visit: http://www.weather..gov/peac/update.php Also see: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ . enso_advisory/ensodisc.pdf 3rd Quarter, 2016 Pacific ENSO Update Page 3 TROPICAL CYCLONE ACTIVITY The PEAC archives western North Pacific tropical cyclone (TC) numbers, track coordinates, and 1-minute average maximum sustained wind taken from operational warnings issued by the Joint Typhoon Warning Center (JTWC) of the U. S. Air Force and Navy, located at Pearl Harbor, Hawaii. Western North Pacific tropical cyclone names are obtained from warnings issued by the Japan Meteorological Agency (JMA), which is the World Meteorological Organization's Regional Specialized Meteorological Center (RSMC) for the western North Pacific basin. The PEAC archives South Pacific TC names, track coordinates, central pressures, and 10-minute average maximum sustained wind estimates from advisories issued by the Tropical Cyclone Warning Centers at Brisbane, Nadi, and Wellington. The numbering scheme and the 1-minute average maximum sustained wind estimates are taken from warnings issued by the JTWC. There are sometimes significant differences in the statistics (e.g., storm maximum intensity) for a given cyclone among the agencies that are noted in this summary. Tropical Cyclone Summary As anticipated far in advance, TC activity in the western North JAN - JUL Pacific was very low during the first half of 2016. The season had 2015 a very late start, with the first named storm (Super Typhoon Nepartak) reaching tropical storm intensity on the 3rd of July and then becoming an intense (150 kt) super typhoon on the 6th of July after a period of rapid intensification. Also as anticipated, the TC activity (what there was of it) during the first half of 2016 was displaced to the west and north of average, in stark contrast to the activity during the first half of 2015, which was unusually abun- dant and displaced eastward in to Micronesia (Fig.