Aus Seasonal Briefiing July 2018

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Seasonal Forecast Australia – National Electricity Market Updated 13 JULY 2018

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Overview 2 Teleconnections El Nino Southern Oscillation (ENSO) Index – current and forecast Indian Ocean Dipole (IOD) Index – current and forecast Six Month Forecast (ECMWF SEAS5 Seasonal Forecasting System) Temperature & Precipitation anomaly forecasts Forecast Maps Temperature, precipitation, surface pressure, and sea-surface temperature forecasts

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ENSO – Current conditions 3 The NINO 3.4 SST Index is currently in a neutral phase, but a recent warming trend has the index approaching weak El Nino criteria. strong moderate weak neutral weak moderate ← La Nina El Nino →

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ECMWF 4 BoM NCEP ENSO – Forecasts

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ECMWF’s El Nino Forecast: How Accurate is it? 5 Last Year: By July, the signal for an El Nino summer had already dematerialised, and further trended to a weak La Nina in Aug/Sep. This Year: The prediction for El Nino conditions for the upcoming summer has continually strengthened in the last few months. ENSO forecasts suffer from a “predictability barrier” through the autumn months: a period of traditionally low forecast accuracy. From May onwards, ENSO forecasts for the following summer become increasingly more confident, and can often exhibit a trend from one predicted state to another. Here is a look at last year’s and this year’s forecast progressions:

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6 A growing consensus of long-range models are predicting a weak to moderate El Nino event for the upcoming Summer 2018-19 season. El Nino events are typically associated with warmer temperatures and drier conditions. ENSO – Forecasts

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IOD – forecasts 7 What is the Indian Ocean Dipole? The Indian Ocean Dipole (IOD) is a sea-surface temperature oscillation in which the western Indian Ocean becomes alternately warmer and then colder than the eastern part of the ocean. This phenomena occurs during the winter-spring months, with Q3 being the most affected. Current IOD Forecast The model consensus is predicting neutral IOD conditions through the rest of 2018; however, some models are suggesting a potential positive IOD event.

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Positive IOD Events – Impacts on Precipitation 8

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Positive IOD Events – Impacts on Temperature 9

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ECMWF SEAS5 – Temperature Anomalies 10

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ECMWF SEAS5 – Temperature (change from previous forecast) 11

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ECMWF SEAS5 – Precipitation 12

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13 ECMWF SEAS5 – August / September / October Pressure Anomaly Sea Surface Temperature Anomaly Precipitation Anomaly Temperature Anomaly NINO 3.4 IOD

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14 ECMWF SEAS5 – September / October / November Pressure Anomaly Sea Surface Temperature Anomaly Precipitation Anomaly Temperature Anomaly NINO 3.4 IOD

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15 ECMWF SEAS5 – October / November / December Pressure Anomaly Sea Surface Temperature Anomaly Precipitation Anomaly Temperature Anomaly NINO 3.4 IOD

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16 ECMWF SEAS5 – November / December / January Pressure Anomaly Sea Surface Temperature Anomaly Precipitation Anomaly Temperature Anomaly NINO 3.4 IOD

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