An extraordinary end to Tropical Cyclone Kelvin
Thurs 22 Feb 2018
Tropical Cyclone Kelvin (see AWN earlier) backtracked eastwards then was upgraded to Category 2 level as it crossed the WA coast at Anna Plains Station, 160km SW of Broome, at 07.00 WST 18 February with wind gusts to 150km/h. Good reports on the event are on the Guardian, Reuters, Al Jazeera and ABC News.
A most unusual feature of the cyclone was that it strengthened for several hours after crossing the coast; most cyclones weaken almost immediately as their source of energy, drawn from warm ocean water beneath, is cut off and roughness from the land surface distorts the cyclone's circulation. Kelvin's eye even became more organised as it headed SSE into the Australian interior, and it was still a Category 1 cyclone as it passed Punmu, nearly 400km inland, over 24 hours later [Andrew Miskelly]. It is also unusual for a weaker cyclone to retain its strength like this for so long after landfall. Jeff Masters in his blog - scroll down to the radar images here - commented at length on these features and their possible causes. The BoM also speculated to ABC News that the great inland sea of warm, brown water that has cut the area's main Great Northern Highway could have acted as an extension of the warm sea water, sustaining Kelvin after it left the Indian Ocean while wetted desert sands may have maintained it farther inland creating a type of "landphoon" [see Savanna Explorer, Le Coin Météo†].
On 19 February, the BoM posted a remarkable list of records set at Broome. The town has had its wettest year in observations going back to 1889 - and it is only February! It has had its wettest month of January and wettest February day on record, as well as its second wettest January day and second wettest month of February which may yet be eclipsed by the time February ends. ABC News ran this retrospective of the rain in Broome on 20 February. It also ran follow-up stories on the flooding and its effects, with some good photos, on 18, 19 and 21 February.
Even after Kelvin passed into its extra-tropical phase, moving down the eastern side of WA, across the Nullarbor Plain, and out into the Great Australian Bight on 22 February, it retained its active circulation. On the Nullarbor, it gave Eucla 79.2mm in the 24 hours to 0900 WST 22 February, its highest daily total since 16 February 1960 and nine times the station's median rainfall for the whole month.
Details of the history of Kelvin are published in the BoM's Cyclone Report, and Floodlist posted this flood report.
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