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Cyclone Olga

January 2010

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Cyclone Olga

Qldtc 20100123Olga

Tropical Cyclone Olga was initially analysed as a tropical low situated in the Pacific Ocean to the northeast of the Solomon Islands on 19 January. The low then moved in a southwest direction into the Coral Sea before it developed during the early hours on 23 January into a tropical cyclone. Olga then intensified further later that day into a category 2 system as it approached the Queensland east coast.

Olga initially crossed the coast as a tropical low approximately 25km south of Cairns early on 25 January before it began to make the journey westwards across inland Queensland and into the Roper McArthur district of the Northern Territory.

Olga then found itself under the influence of an upper trough crossing south-eastern Australia by 29 January, which then steered the system in an easterly direction over southern Gulf of Carpentaria waters. Once the system moved over the warm waters of the Gulf, Olga managed to once more re-intensify into a tropical cyclone within 12 hours.

Tropical Cyclone Olga finally made landfall about the Gulf Country coast for the final time early on 30 January as a category 1 system. The system then continued to move in a southerly direction across inland Queensland while also delivering widespread rain to much of the state.

While tracking across the Coral Sea Olga interacted with Ex-Tropical Cyclone Neville in a manner referred to as the Fujiwhara Effect, whereby two low pressure systems can influence each other to the extent that they can tend to orbit each other like two planets. At their closest point the two systems came within less that 300km of each other on the night of 23 January.

The combined effects of TCs Olga and Neville

Tropical Cyclone Olga formed over the Coral Sea near Willis Island to the east of Cairns early on the 23^rd and tracked west and deepened to category 2 late that evening. During the 24th it continued tracking toward the coast before becoming almost stationary. It weakened below cyclone strength and recurved briefly before making a coastal crossing between Cairns and Innisfail early on the 25th.

The combined effects of Tropical Cyclone Olga, Ex Tropical Cyclone Neville, the monsoon and a convergent southeast trade flow to the south brought heavy rainfall and flooding to much of the northeast tropical coast.

Ex Tropical Cyclone Olga continued west overland passing by Georgetown and Croydon before skirting the southern coast of the Gulf of Carpentaria beginning a big wet for the Gulf Country. Olga reformed briefly into a cyclone in the southern Gulf waters during the 29th and moved to the southeast Gulf accompanied by heavy rainfall and damaging winds. Both these systems enhanced the seasonal monsoonal activity bring flooding rains to the north. Tropical Cyclone Olga weakened to a tropical rain depression after crossing the coast near Karumba and continued across the interior to be near Longreach at the end of January.

Exceptionally heavy rainfall was recorded in the vicinity of the low and also near the monsoon trough as it shifted south along the east coast to lie to the south of Mackay at the end of the month. The heavy rainfall focused near the monsoon trough along the east coast also coincided with the king tides at this time of year to cause sea water coastal inundation at some locations, including near Townsville and Mackay.

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