Indian Ocean Dipole Shifts Negative, Albeit Weak

Discussion: Currently, the Indian Ocean dipole is in weak positive phase. The western basin is 0.32C warmer than the eastern basin identifying the +IOD regime (Fig. 1-2). The IOD trend of recent weeks is to drift into the weak positive phase. The IOD forecast was a shift into the negative phase for the last third of 2024. Due to the recent rewarming of the western tropical North Atlantic, the -IOD forecast remains, but is generally weaker and not all models project -IOD. The International multi-modal ensemble (IMME) indicates -IOD developing early in Q4/2024 (Fig. 3). The Climate Impact Company IOD analog forecast indicates weak -IOD evolving by OCT/NOV (Fig. 4). In summary, a weak -IOD remains forecast for Q4/2024 although forecast confidence has lowered and the -IOD pattern is likely weak and lacking in longevity.

Fig. 1-2: Comparing the west and east Indian Ocean tropical basin SSTA.

Fig. 3: The International multi-modal ensemble global SSTA forecast for October 2024 identifies development of the negative phase Indian Ocean dipole regime.

Fig. 4: The Climate Impact Company Indian Ocean dipole analog forecast.