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Heavy rain is expected in parts of Otago from this evening, while more wet weather looks to be on the way for much of the country in coming days.
Today's forecast showed a moist northwest flow covering the southern South Island this morning, bringing heavy rain to Fiordland and southern Westland.
A heavy rain warning was in place for Westland from Franz Josef southward as well as Fiordland over the next 24 hours.
MetService meteorologist Mark Bowe said heavy rain was also expected around the headwaters of Otago rivers and lakes, where a heavy rain watch in place.
The question remains: will it hit New Zealand or will it swoop past and wreak havoc on Australia instead?
Weatherwatch this morning said it still remained unclear if the cyclone would directly hit the country but rain was on its way regardless.
The world's two most trusted weather services when it came to predicting cyclones, Global Forecast System and ECMWF, still disagreed on whether it would track towards New Zealand this weekend or do a u-turn back into the tropics, Weatherwatch said.
But both models were picking a new low to form around New Zealand regardless of Oma's precise tracking, meaning there would be rain for both islands - but where exactly and how much was unclear. There remained the possibility most of the rain would fall at sea around New Zealand, Weatherwatch said.
Bowe said forecasters were awaiting the latest prediction models for the path of the cyclone.
The cyclone was located west of Malekula, Vanuatu where it has reported to have lead to flooding and damage.
Emergency services and aid agencies are on alert as more details emerge of the effects of Oma.
"Tropical Cyclone Oma should move southwest away from Vanuatu over the next couple of days, and may reintensify into a category 3 system as it moves past New Caledonia.
"It should continue to move south-southwest during Wednesday and Thursday, to lie over the southern Coral Sea by the end of Thursday."
Most model outlooks showed the system would recurve towards the southeast on Friday.
Bowe said weather for the next two days was mostly fine, although heavy rain was predicted on the West Coast of the South Island in coming days.
"Today the North Island is going to be mostly fine, there may be the odd shower around Northland."
There would be some isolated afternoon showers in the country's northern-most region but the main action was rain brought on by fronts in the South Island.
"There are a couple of fronts moving onto the South Island. That means heavy rain for the west of the South Island. Eastern areas north of Ashburton should be mostly fine."
Weatherwatch said a colder change arriving on Friday could cause temperatures to drop "significantly" this weekend.
This Sunday and Monday daytime highs around a large portion of Southland, Otago and Canterbury will be just 11 to 14 degrees at the hottest part of the day.