+IOD & El Nino Modoki = Increased Heat Risk & Worsening Drought Executive Summary: A positive phase of the Indian Ocean Dipole is developing and should last well into upcoming summer. +IOD favors dryness across western and southern Australia. Meanwhile an El Nino is likely for late 2018 and into 2019. When El Nino is in-place a drier than normal national climate occurs. The combination of +IOD and El Nino are red flags for worsening drought ahead. Fig. 1: Percent of normal rainfall across Australia since April 1, 2018. Climate discussion: The outlook for the next 3-6 months remains governed by the influence of an evolving positive phase of the Indian Ocean Dipole and an El Nino episode whereas the bulk of the eastern equatorial Pacific warming is biased toward the Dateline (Fig. 1). ENSO events where equatorial Pacific warm SSTA are biased toward the Dateline are known as El Nino Modoki. During the past couple weeks sudden warming has developed off the northwest coast of South America. If this warming continues a more conventional El Nino will evolve. If the warming off the coast of South America weakens the El Nino Modoki is more likely. Surface and subsurface anomalous warmth near the Dateline has been persistent the past 1/2 year with no obvious change in sight. Climate outlooks: The outlooks are based on +IOD and El Nino Modoki through summertime and just El Nino Modoki next autumn. Monthly forecasts for October and November are provided. The summer and autumn outlooks are compared to previous forecasts. October 2018: The mid-spring outlook is hot across Western Australia with dryness across most of the continent especially North-central areas and eastern New South Wales to southeast Queensland. The Australian drought worsens during October. Fig. 2-3: The Climate Impact Company October 2018 temperature and precipitation anomaly outlook for Australia is indicated. November 2018: Widespread anomalous heat is forecast as the spring season ends. The warmest anomalies are across the interior eastern portion of the continent. The precipitation outlook is very dry across the north and east continent. Drought conditions continue to worsen. Fig. 4-5: The Climate Impact Company November 2018 temperature and precipitation anomaly outlook for Australia is indicated. DEC/JAN/FEB 2018-19: Meteorological summer indicates the springtime anomalous heat continues but shifts westward and is focused on Western Australia. South and southeast Australia are also somewhat hotter than normal. Drought conditions in these regions certainly worsens for summertime. The forecast indicates some tropical rainfall on the East Coast and possibly 1 or 2 places well inland but not enough to reverse a drought condition. Most of northern portions of Australia are also hotter and drier than normal for the summer season. The forecast is not quite as wet and cool for the northeast portion of the continent as previously indicated. Fig. 6-7: The Climate Impact Company DEC/JAN/FEB 2018-19 temperature and precipitation anomaly outlook for Australia is indicated. The previous forecast is below. MAR/APR/MAY 2019: The autumn 2019 outlook changes as the southeast portion of the continent reverses from very warm to cool and anomalous heat is focused on western and northeast continent. A mostly dry climate continues. Fig. 8-9: The preliminary Climate Impact Company MAR/APR/MAY 2019 temperature and precipitation anomaly outlook for Australia is indicated. The previous forecast is below.