NZ Herald: NZ’s cooler waters protect us from the worst storms

Isaac Davison writes in the New Zealand Herald about the factors which protect New Zealand from storms such as Cyclone Yasi.

The major factor is New Zealand’s waters, which are generally too cool to spin off large tropical cyclones.  Further, New Zealand barely feels the effects of the warmer currents which come with La Nina cycles, and which also increase the risk of cyclones for countries like Australia.

An excerpt: (read in full here)

“This was evident in Cyclones Vania and Zelia, which last month burned out before they reached New Zealand after being measured as category three in the Pacific Islands. Cyclone Yasi similarly would have been disarmed by this colder water if it approached New Zealand.

“Our biggest storms occur when weakened cyclones meet another storm system.

“Niwa climate scientist Jim Renwick says, “These tropical cyclones can drift out of the tropics, retain their identity, and provide the punch for an existing storm.”

“He said the best-known example of this phenomenon occurred in 1968, when tropical storm Giselle collided with a polar storm from the Southern Ocean over Wellington. The storm sank the ferry Wahine in the harbour, killing 51 people.”