Australian Drought to Worsen as Bureau of Meteorology/Australia Identify Positive Indian Ocean Dipole/Approaching El Nino
Discussion: About 75 to 80% of Australia has been desperately dry since April 1. Little or no rainfall has been observed during that period over much of central and northern portions of Australia. The result (as of Aug. 1) is a profound drought condition affecting much of Australia (Fig. 1). The drought has worsened in August.
Fig. 1: Soil moisture anomaly analysis across Australia for July 2018.
Fig. 2: Since April 1, 2018 the 500 MB anomaly analysis identifies a strong dry/warm high pressure ridge across Australia.
The climate pattern responsible for generating the dryness is an elongated high pressure ridge stretched west-to-east across Australia since April 1 (Fig. 2). The upper ridge has produced steady dry and warm conditions and blocked the intrusion of any strong cold fronts bringing rainfall. Interestingly, the persistent high pressure ridge is not linked to any particular SSTA pattern in the South Pacific or South Indian Ocean although recent cooling of the ocean surface west and northwest of Australia representing onset of the positive phase of the Indian Ocean Dipole (-IOD) is a drought enhancing condition for Australia.
The climate outlooks for Australia are contingent on ENSO and Indian Ocean dipole (IOD). The Bureau of Meteorology/Australia indicates an evolving El Nino episode with onset during spring (Fig. 3). Meanwhile the IOD regime has entered the positive phase which is forecast to last several months (Fig. 4). +IOD and El Nino are drought enhancers for Australia.
Fig. 3: The Bureau of Meteorology/Australia ENSO outlook indicates El Nino onset during spring.
Fig. 4: The Bureau of Meteorology/Australia IOD outlook indicates weak positive phase the next 3 months.
The Climate Impact Company climate outlooks for Australia (please see web site) indicate worsening drought through spring and early summer. The worst drought on record is likely for Australia given current conditions and the +IOD/El Nino scenario ahead.