Wind farms may fool forecasters

As long as meteorologists know where the wind farms are they are less likely to cause issues. Photo / Supplied

Moving turbine blades can look a lot like a thunderstorm or even a tornado on radar

Storm clouds are gathering on the horizon for New Zealand weather forecasters, as the number of wind farms grow.

Wind farms generate a storm-like appearance on weather radars, which has caused incorrect forecasts overseas and is now prompting predictions of similar problems here.

Doppler radars used by meteorologists detect storms by picking up movement in the air, MetService chief forecaster Rob Stainer said.

Stationary objects such as buildings and mountain ranges were easily filtered out, but moving wind turbine blades could look a lot like a thunderstorm or even a tornado on the radar.

Problems seemed to occur when wind farms and radar stations were set up within about 18km of one another.

It could cause some serious issues - a tornado alert was recently issued in the United States after a particularly active wind farm was misinterpreted by one meteorologist.

The alert was quickly recalled, but with the numbers of wind farms worldwide on the rise, it seemed unlikely that the mistake would be the last.

Mr Stainer said that while the wind farm anomalies had been observed in New Zealand, as long as meteorologists were aware of them they would not be likely to cause issues.

"If you know where the wind farms are, you're reasonably able to identify these particular echoes, because they're always in the same spot."

Radar used by New Zealand meteorologists could take readings from different altitudes and, since anomalies caused by wind farms occurred only close to the ground, it was fairly easy for a meteorologist to tell thunderstorms from turbines.

Mr Stainer said with a worldwide increase in wind farms, the anomalies were unavoidable.

"We've known that this is a problem with it, and it's going to be an increasing problem around the world."

- NZPA