MetService spokesman Peter Kreft says the storm is "one of the largest and deepest lows we've seen for some years."
The severe storm is expected to hit Auckland some time between midday Saturday and midday Sunday.
"By the time this system reaches northern New Zealand on Saturday, it is likely to have significant destructive potential," Mr Kreft says.
"The real issue will be the wind, with gusts of more than 110km/h expected."
The rapidly intensifying storm is expected to strike Northland first, then Auckland before reaching Bay of Plenty and Gisborne late Sunday, MetService said.
Far North District Council civil defence teams and contractors are on stand-by ready to deal with any fall-out from the storm.
Mr Duncan said: "It is going to deepen rapidly and has the potential of bringing damaging winds, flooding rains, big seas and strong rip tides. It may well be the most intense sub-tropical storm of the decade".
He said the air pressure with this system could drop to 967hPa for a time on Saturday which he says is extremely rare for areas near Auckland.
"This could help create one of the biggest storm surges seen in the upper North Island for several years. If this prediction eventuates we could see storm surges flooding low lying eastern coastal areas from Northland to Auckland and across Coromandel and Bay of Plenty. It may also pose a serious risk for low lying areas around the Firth of Thames which is particularly vulnerable to northern storm surges". (MSN Xtra news)