Fog takes hold as region shivers

The last of the heavy fog sat over parts of seafront Napier until late yesterday morning. Photo / Paul Taylor

The coldest night of the year to strike Napier and Hastings provided the perfect conditions to create fog which caused an inbound Air New Zealand flight to be turned away from Hawke's Bay Airport yesterday.

The fog, which began to spread fast around sunrise, was reported as far south as Waipawa and shrouded parts of Napier so thickly visibility was reduced to about 50m by 8am.

It was about that time the Air New Zealand flight from Auckland was forced to circle several times waiting for a break in the fog layer.

But the break did not happen in time and it turned back, resulting in an 8.10am flight to Auckland being cancelled.

But the fog across the Westshore areas did lift within an hour and other flights were not affected.

Fog patches remained over the port area until about 10.30am.

Heavy fog was also reported in Hastings and Central Hawke's Bay, with police describing it as widespread and thick.

Senior Sergeant Kris Eckhold said patrols on SH50 and southern SH2 stretches reported too many drivers travelling too quickly for the conditions.

"And a lot of the following distances were far too close."

With temperatures slipping below freezing, there was the risk of ice forming but that prospect, and reduced visibility, did not appear to faze some drivers, Ms Eckhold said.

Many drivers also drove with headlights off.

"In those conditions, put the lights on low beam, slow down and stay well behind the car in front."

She said when patrols went out about 7.30am, the temperature was logged at -6C in some spots.

The sub-zero drop created the right conditions for fog to form, MetService meteorologist Rebekah LaBar said.

Napier's temperature hit -2.5C, which created 100 per cent humidity and moisture saturation, causing fog to build up.

Ms LaBar said fog often thickened at sunrise as the sun added dry air with the moist air, although once the sun was higher in the sky it caused the temperatures to rise off the saturation level.

She said dense fog was not uncommon in many parts of New Zealand.

"Napier can be a tricky one to forecast for it," she added.