08/11/2022, 10:01 am EDT

Indian Ocean Dipole Outlook

Highlight: -IOD onset arrives. Moderate-to-strong -IOD ahead.   Fig. 1: Australia Bureau of Meteorology is forecasting an intensifying Indian Ocean Dipole ahead. Discussion: Another negative phase of the Indian Ocean Dipole (-IOD) has started as waters have cooled in the eastern equatorial Indian Ocean while northwest of Australia SSTA is warmer than normal. The latest Australia Bureau of Meteorology (ABM) IOD forecast indicates intensification is ahead with peak intensity of the negative phase occurring in September (Fig. 1). -IOD is forecast to linger through the end of 2022. Notable is the -IOD projection by ABM last April indicating a -1.5 index for August (Fig. 2). Verification indicates -IOD initiates in August at approximately half the intensity expected. Is the -IOD forecast valid for the remainder of 2022 overdone? Currently, soil moisture anomalies across Australia indicate moderate-to-strong wet signatures across north and east portions of the continent while dryness has dominated west and south portions of Western Australia (Fig. 3). The wet pattern across the north and east continent is mostly caused by a lengthy La Nina climate. The La Nina pattern remains and may gain some strength during the next 1-3 months. Coupled with -IOD, a wet forecast is indicated by NCEP CFS V2 as the model features a strong upper-level (wet) low-pressure trough across southern continent for springtime and the upper trough remains albeit weaker on the East Coast for upcoming summer (Fig. 4-5). Fig. 2-3: ABM projection of -IOD from a forecast issued last April and the July 2022 Australia soil moisture rankings. Fig. 4-5: NCEP CFS V2 upper air forecast across Australia for spring 2022 and summer 2022-23.