Updated 5.43pm: Civil Defence officials in Gisborne are preparing for what could be the largest cyclone in New Zealand's recorded history.

Tropical Cyclone Pam is expected to be upgraded from category 4 storm to a category five tomorrow morning.

Head of Gisborne's Emergency Management, Richard Steele says it's already larger than Cyclone Bola in 1988.

"It's certainly bigger than what Cyclone Bola was at this stage."

Cyclone Pam is slowly but surely moving away from Solomon Islands and gradually heading towards Fiji and Vanuatu.

It's being described as "nasty" by weather expert Richard Green, now classed as a Category Four cyclone.

He claims it brings extremely serious weather conditions in terms of rain intensity and wind strength.

MetService is closely watching Tropical Cyclone Pam as the severe storm heads towards our shores.

Meteorologist Peter Little says its path could change.

"A lot can happen between now and then. Cyclones can be quite fickle beasts, and we'll certainly be keeping a very close eye on it."

Weather expert Richard Green says by the weekend it will bring dangerous swells to northern and eastern parts of New Zealand.

"I would say come late Sunday and Monday the weather conditions will certainly deteriorate for parts of Northland, Auckland, Bay of Plenty, also Gisborne and northern Hawke's Bay as well."

Green says it will hit eastern areas of the country that have been crying out for rain.

"The sad thing is that when we've had such a prolonged dry spell, the ground is so hard, so when the rain is so heavy it'll just bounce off and run off, so there is a chance of some flooding in some very dry areas."

Check out where Cyclone Pam is with Earth Wind Map