Tropical cyclone Zaka - the latest storm to develop over the Pacific Ocean after cyclone Yasi pummelled Queensland last week - was tonight passing the East Coast as a small storm.

After passing west of Raoul Island, the largest and northernmost of New Zealand's main Kermadec Islands, Zaka headed for New Zealand in a weakened state as it entered cooler waters, analyst Philip Duncan said.

"Despite the centre being just 200km away from land, the system may not even bring cloud to the eastern tip of the North Island," he said tonight.

"The system is so small it may only bring a period of easterly winds for an hour or two this evening north of Gisborne."

But the "low" could drive in some rough seas over the next 12 to 24 hours around East Cape, Gisborne and Mahia Peninsula. Swells near the centre of the low will be around 5m high with waves reaching 2m to 3m around East Cape and Gisborne until tomorrow afternoon.