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Positive Indian Ocean Dipole strengthens, Enso remains neutral in Pacific Ocean


MELBOURNE, Australia – In the tropical Pacific Ocean, the El Niño–Southern Oscillation ( ENSO ) remains neutral, reports the Australian Government Bureau of Meteorology in its latest wrap up. The positive Indian Ocean Dipole (IOD) has strengthened, continuing its influence on the climate of Australia and other parts of the globe.

The very strong positive Indian Ocean Dipole event persists, characterised by cooler waters to the northwest of Australia and warmer waters further west. Values of the IOD index over the past fortnight have strengthened, and the latest value of +1.76 °C is the strongest positive weekly value since at least 2001.

All international climate models surveyed by the Bureau indicate the positive IOD is likely to persist at least until the end of the southern hemisphere spring. At the beginning of summer, the IOD pattern normally breaks down as the monsoon trough migrates into the southern hemisphere.

Typically, a positive IOD brings below average winter–spring rainfall to southern and central Australia, with warmer days for the southern two-thirds of the country. Positive IOD events are often associated with a more severe fire season for southeast Australia.

In the Pacific Ocean, the El Niño–Southern Oscillation (ENSO) remains neutral. Most atmospheric indicators are neutral, although the Southern Oscillation Index (SOI) is negative due to very high atmospheric pressures at Darwin. International climate models forecast neutral ENSO for the remainder of 2019, and into early 2020.

When ENSO is neutral, it has little effect on Australian and global climate, meaning other influences are more likely to dominate.