West Coast more at risk of tornadoes than rest of NZ

The West Coast is New Zealand's tornado "hotspot", meteorologists said today after one ripped through Greymouth.

"The West Coast is probably the area that gets the most tornadoes," Metservice forecaster John Crouch told NZPA today.

This was partly because of the topography, which meant it got a lot of rain and thunderstorms.

"We get bands of thunderstorms on the West Coast because we get the colder westerly winds coming in off the Tasman, hitting the land, and air's getting lifted up so that it becomes quite unstable," Mr Crouch said.

The West Coast experienced a lot of tornadoes because the Southern Alps turned strong winds.

"They come on shore as a northwesterly, and at low altitudes they get turned by the mountains into north to northeasterly flow at the surface.

"The combination of winds turning as they come on to the mountains, combined with thunderstorms, sometimes allows the thunderstorms to start rotating".

These conditions could lead to tornadoes being spawned, he said.

Mr Crouch said that there was an unstable northwesterly flow onto the West Coast at the moment.

"It has been spawning thunderstorms, pretty much the length of the West Coast from Karamea down to Fiordland, and there have been several bands (of thunderstorms) moving through this morning.

"Today's tornado has obviously formed on one of these bands," he said.

In June 2003, about 20 businesses were damaged when a tornado cut a swathe through the downtown area and caused damage costing more than $300,000.

The 2003 tornado swept in off the Tasman Sea at about 9.45am, wreaking havoc on the western end of the central business district, snapping concrete power poles and knocking over street lights.

A similar tornado ripped through Greymouth in the early hours of March 28 2001, wrecking houses.

No one was injured then, but glass shattered and iron buckled in some homes.

- NZPA