Two Climate Alerts: +IOD Begins to Fade; Stratospheric Warming Ahead

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Two climate alerts are issued. The positive phase of the Indian Ocean Dipole causing the Australian drought is beginning to ease increasing risk of returning beneficial rainfall late rthis summer season. A stratospheric warming event initiates in 10 days over Alaska and could cause an arctic outbreak in North America in early December.

CLIMATE ALERT 1: +IOD beginning to weaken.

Fig. 1: A classic +IOD pattern remains in-place. However, warming off the northwest coast of Australia is spreading toward the cool SSTA region in the eastern Indian Ocean signaling a weaker +IOD ahead.

Discussion: The latest wet monsoon on record recently ended across India where soil moisture may be the wettest on record for this time of year. Meanwhile harsh drought is affecting much of Australia. The catalyst to these two climate regimes has been one of the strongest positive phase Indian Ocean Dipole regimes on record. There are signs of weakening of the +IOD pattern is beginning as waters off the northwest coast of Australia are warming and shifting toward the equator. A weaker +IOD signals increased risk of wet episodes for later summer in Australia.

CLIMATE ALERT 2: Stratospheric warming event ahead.

Fig. 2: The GFS ENS identifies a stratospheric warming event over Alaska beginning in 10 days.

Discussion: All models show the second stratospheric warming episode of the 2019-20 northern hemisphere cold season appears in 10 days over Alaska and poleward. There is potential for an arctic air mass to emerge due to this event. The only issue is the warm open water south of the polar ice cap at northern latitude which could prevent or slow the arctic air generation.