Flip-Flop on Indian Ocean Dipole Forecast?

Subsurface Equatorial Oceans Water Temperature Observations & Trends Can Foreshadow Climate Ahead
05/16/2018, 12:26 pm EDT
PDO is Neutral BUT is the Longterm Cycle Changing to Warm Phase?
05/18/2018, 11:08 am EDT
Show all

There is concern regarding a possible change in the Indian Ocean Dipole forecast for JUN/JUL/AUG 2018. Warming has taken place in the western Indian Ocean tropics where SSTA are about 1.0C warmer than the eastern Indian Ocean tropics. In April the subsurface eastern Indian Ocean was quite cool indicating the cooling at the surface could continue. The trends identified point toward the positive phase of the Indian Ocean Dipole and not the negative phase as forecast by IOD Experts at the Bureau of Meteorology/Australia. A low confidence scenario here BUT if +IOD forms with an ENSO trend toward weak EL Nino later this year Australian drought worsens.

Of considerable interest is a projected shift in the Indian Ocean Dipole (IOD) out of neutral phase. The Bureau of Meteorology/Australia forecasts evolution of the negative phase of IOD (Fig. 1). However, synoptic trends indicate warming of the western tropical Indian Ocean while both the surface and subsurface are cooling in the eastern Indian Ocean tropics (Fig. 2-3). The synoptic trend indicates the positive phase of IOD is developing. Given the cool subsurface of the eastern equatorial Indian Ocean Climate Impact Company forecasts +IOD for upcoming winter which is likely to enhance Australian drought (Fig. 4).

Fig. 1: The Bureau of Meteorology/Australia Indian Ocean Dipole forecast indicates negative phase for winter 2018.

Fig. 2: Latest Indian Ocean SSTA analysis indicates warm phase of the Indian Ocean Dipole developing as the western IO tropics have warmer.

Fig. 3: The equatorial subsurface ocean temperature anomalies during April 2018 indicate cooling in the eastern Indian Ocean suggesting a trend toward +IOD (cooler eastern IO) ahead.

Fig. 4: If +IOD forms (as trends indicate) instead of –IOD (as forecast by BOMA) a much drier winter occurs across Australia enhancing drought.