A tropical cyclone is likely to form east of Queensland tomorrow and its remnants could possibly strike New Zealand early next week.
Its exact path is still undetermined, with a high pressure system moving up the Tasman Sea potentially to act as a "wall", sending it north of the country.
Niwa principal scientist Chris Brandolino says even if it does sail above New Zealand, the impacts could still be severe - especially for the country's drought-stricken regions where the land is "like concrete".
The system is currently classed as a tropical low and is sitting just off the coast of North Queensland.
The Queensland Bureau of Meteorology forecasts it to become a category 1 tropical cyclone tomorrow evening, and intensify to category 2 by Saturday.
If it forms it will be named Gretel.
Brandolino said based on that trajectory and above-average sea surface temperatures the low could potentially intensify further to category 3, a severe tropical cyclone.
"But at this stage there are more questions than answers. We are most certain it will form a tropical cyclone, and that it will track southeast towards New Zealand.
"But where it goes after this weekend is uncertain."
A major mitigating factor was a large high pressure system moving up the Tasman Sea.
This could effectively act as a "wall" Brandolino says, stopping the yet-to-be tropical cyclone from dropping as far south as New Zealand, and instead passing to the north of the country.
The big question, is which arrives first.
A tropical low in the Coral Sea is expected to form into a tropical cyclone 🌀 by late Friday. It's name will be Gretel.
It will track southeast over the weekend. It's possible, though not certain, NZ receives impacts next week.
If the high moves quick enough, it will push the system well north of New Zealand. However, if the high is too slow, the system - by that stage likely classed as an ex-tropical cyclone - could be lining New Zealand up for a direct hit.
Whichever the track, New Zealand would likely experience some severe weather.
"As these systems move into cooler water they lose some of their intensity, but they still carry significant impacts, and these can also be well away from the centre. So even if it does not cross New Zealand, if it comes close enough we could see strong winds, heavy rain and large waves."
Agriculture Minister Damien O'Connor has classified the current drought in the North Island, parts of the South Island and the Chathams as a "large-scale adverse event".
This image shows the competing high to the southwest, and low to the northwest. Image / Weatherwatch
While a little rain will be beneficial, a huge amount in a short period could be devastating, Brandolino said.
"It might be positive for those on water tanks, but really what we don't want after these long dry spells that has left the land like concrete is a huge amount of rain all at once, which could lead to flooding.
"We might get the sweet spot though, with some rain but not too heavy.
"The advice is to keep a close eye on the forecast and expect some potential severe weather Tuesday and Wednesday next week."
The system also had the potential to bring large waves and offshore winds to the North Island's west coast, and in particular Piha Beach, playing host to an international surfing competition, featuring 11-times world champion Kelly Slater.
"Surfers will love the big waves coming. If the system sits just north of New Zealand we could see some big waves and offshore [easterly] winds, but if it comes too far south we could be in for some hazardous weather and probably not very good surfing."
MetService today said a ridge of high pressure currently dominating New Zealand would hold into the weekend - only loosening its grip over the South Island on Sunday when a front moved up the island.
Sun was forecast for most on Friday, and most of the country was in for a fine weekend too, including during Womad in New Plymouth's Bowl of Brooklands, which will host tens of thousands.
"Though cloud and isolated showers are expected to persist over eastern coasts from Gisborne northward into Sunday New Plymouth and Auckland are looking to see plenty of sun - festival friendly weather for those heading to WOMAD and Pasifika with a hat and sunblock needing to be packed along that picnic blanket and good mood."
In Christchurch, the memorial service for the terror attacks in Christchurch is scheduled for Sunday, which is also expected to attract thousands.
The forecast for Sunday currently showed a cloudy day with a few showers by midday with a cool southerly change.
