Ex­pect more in­tense cy­clones


Auck­land will be met with stronger but less fre­quent cy­clones in the fu­ture, cli­mate sci­en­tists say.

As the most pow­er­ful At­lantic Ocean storm in recorded his­tory tears a path of de­struc­tion across the US state of Florida and neigh­bour­ing coun­tries, it begs the ques­tion: Could such a storm ever hit New Zealand?

With top sus­tained winds of 290kmh, Hur­ri­cane Irma, which killed at least 22 peo­ple in the Caribbean, could in­flict a nat­u­ral dis­as­ter caus­ing bil­lions of dol­lars in dam­age.

For per­spec­tive, the high­est recorded winds in Auck­land over the week­end were about 109kmh.

MetSer­vice me­te­o­rol­o­gist Peter Lit­tle said Auck­land’s nar­row po­si­tion be­tween two seas in the north of the coun­try meant that it, along with North­land, tended to bear the brunt of storms that hit New Zealand.

Cy­clones tended to weaken over land so Auck­land’s po­si­tion closer to the top of the coun­try nearer open wa­ter meant it faced stronger weather sys­tems than the rest of the coun­try.

A cy­clone is a group of thun­der­storms ro­tat­ing around a cen­tral point due to plan­e­tary spin. Air swirls in to­wards the cen­tre in a clock­wise di­rec­tion (in the south­ern hemi­sphere) and is ex­pelled out the top.

There is no ev­i­dence of a trop­i­cal cy­clone ever hitting New Zealand, the MetSer­vice said.

Wind gusts of 205kmh were recorded in Auck­land at Manukau Heads in 1992. New Zealand’s windi­est place on record was Mt John in Can­ter­bury in 1970 with wind gusts up to 250kmh.

Niwa principal sci­en­tist Chris Bran­dolino said mod­el­ling fu­ture cli­mates was com­pli­cated, but emerg­ing re­search showed that trop­i­cal cy­clones could be­come less fre­quent but stronger.

Vic­to­ria Univer­sity cli­mate expert James Ren­wick said while New Zealand would not be directly af­fected by trop­i­cal cy­clones some of New Zealand’s most ex­treme storms came from ex-trop­i­cal cy­clones.

These were trop­i­cal cy­clones that had left the trop­ics and re­formed as mid-lat­i­tude storms due to strong west­er­lies and lower sea tem­per­a­tures.

For ex­am­ple in 1968 the ef­fects of Cy­clone Giselle were re­spon­si­ble for sink­ing the Lyt­tel­ton to Welling­ton ferry the Wahine in Cook Strait, and in 1998 the ef­fects of Cy­clone Bola caused heavy flood­ing across the coun­try.


Over the week­end Auck­land’s high­est recorded winds were gusts of about 109km.

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