Cyclone Oma might look "less likely" to strike New Zealand but will still fuel bad weather. Forecasters at Weather Watch warn an "unpredictable" low is going to form on Sunday, creating pockets of "severe weather" - including gales, heavy rain, and big seas. The Severe Category 3 tropical storm is currently moving from the Coral Sea. Updated computer models say there's only a 25 percent chance of it brushing the northern regions. But as it heads down, it's pulling down a lot of tropical energy closer to New Zealand. At the same time an area of high pressure east of New Zealand will pull down more sub-tropical nor'easters.<doc-sep>MetService forecasts a lot of rain across New Zealand for the week ahead. Will Tropical Cyclone Oma hit New Zealand or won't it? Computer models are battling it out over TC Oma's possible severe impact on the country at the weekend. Two of the most trusted models - the United States' GFS and the European ECMWF - are taking opposite views of where Oma may end up, whether that is as a tropical cyclone or a former tropical cyclone. Windy.com The American GFS model on the Windy.com website puts the former tropical cyclone Oma directly over central New Zealand by Sunday evening, Feb 24, 2019. This scenario is likely to change before then. But they agree a large low-pressure area may deepen east of central New Zealand on Sunday, accompanied by heavy rain and high winds in places, and dragging up very cold southerly air, bringing high country snow, from well south of the country. READ MORE: * Former cyclone Gita crosses New Zealand, leaving destruction in its wake * Emergency services on high alert as Gita slams into Nelson and Tasman * Weather forecasters challenged by recent bad weather * Forecasting the weather when you don't know - precisely - what's happening now Unusually high tides were also expected in Christchurch on Wednesday, Thursday and Friday, which could bring surface flooding. Windy.com The European ECMWF model on the Windy.com website shows a less intense low-pressure system, which is not the remains of Tropical Cyclone Oma, over central New Zealand next Sunday evening, Feb 24, 2019. This scenario could, of course, change. The latest information from the Fiji Meteorological Service showed Oma at Category 2 strength early Monday, west of Vanuatu and north of New Caledonia. It was expected to move southwest over the next few days, increasing to category 3 strength by Wednesday. MetService meteorologist Mark Bowe said there was "still a lot of uncertainty in the models, not agreeing where Oma should go". "Regardless, there is going to be quite a lot of rain across New Zealand by this Friday. It'll actually be rainy for most." BRADEN FASTIER / STUFF Lyn Rombouts among tree waste on her property, beside Shaggery Creek, near Motueka, after ex-Tropical Cyclone Gita hit the region in February 2018. Blue Skies Weather forecaster Tony Trewinnard said after six weeks of settled, dry and often very warm conditions due to blocking high-pressure, "this is the 'ka-boom' weekend". "We need to give a heads-up that there is severe weather on the way, from Sunday through to Tuesday [next week], and to think about how we might cope if there is disruption. "There's a lot of potential for a lot of stuff to happen. We are looking at several days of severe weather around the country - some people will see gales or worse, heavy rain, and very cold temperatures with snow on higher ground. BRADEN FASTIER/STUFF A man walks through floodwaters to retrieve his dog in Riwaka, Tasman, after heavy rain from ex- Tropical Cyclone Gita flooded parts of New Zealand in February last year. "Those things are probably going to happen, but it's too early to flesh out the detail of what is going to happen exactly where and when. "We've got a week to get our heads around it. We don't always have that luxury." A year ago this week, ex-tropical cyclone Gita carved across New Zealand. TASMAN DISTRICT COUNCIL/SUPPLIED The badly damaged Carter Rd bridge near Collingwood as a result of ex-Tropical Cyclone Gita in February last year. Flooding and wind damage was especially bad in Taranaki, Tasman and along the West Coast. States of emergency were declared in Taranaki, Nelson-Tasman, the Selwyn district, Grey district, Buller district, Westland district and Christchurch city. The GFS computer model predicts a hit on central New Zealand on Sunday afternoon. However, the ECMWF model forecasts that Oma will remain near the Queensland coast, but a deep depression will develop rapidly over New Zealand anyway. Debris covers a swath of the Otuwhero River, near Marahau, after ex-Tropical Cyclone Gita hit the Tasman district on February 20 last year. "The Tasman Sea is kicking off," Trewinnard said. "Even if you take that tropical cyclone out of the picture, the models are still giving us a severe weather weekend." WeatherWatch head forecaster Philip Duncan said high pressure - "like an invisible barrier in the sky" - near Tasmania was "stumping" the computer models. He estimated a "50-50 chance" of severe weather from ex-TC Oma. "A large cooler southerly flow should be moving in to the New Zealand area by this Friday and the weekend, but if Oma directly comes in that will pull down very warm tropical air with it from the north. "If the two meet, then even bigger rain clouds may be generated over New Zealand. There are a lot of moving parts to this. "The GFS is showing a direct hit while ECMWF shows Oma doing a 180-degree turn and backtracking north again. Many other models show the low sliding into the New Zealand area while becoming extra-tropical, the technical change within a storm when a tropical cyclone drops far enough south). "It is very much a waiting game for the two models to align," Duncan said. * Comments on this story are closed<doc-sep>Whether Cyclone Oma hits New Zealand or not this weekend, Kiwis should brace themselves for a wild mix of heavy rain, wind, plummeting temperatures, and even snow. Cyclone Oma is currently bearing down over the north of New Caledonia, where Niwa forecaster Ben Noll told Magic Talk's Peter Williams the storm was causing issues for meteorologists. "It actually knocked out the radar system up there... that speaks to the strength of this system, and that is something we will be keeping a very close eye on," he said. While it is still up in the air whether Oma will strike New Zealand, either way, Mr Noll said Aotearoa will still be battered from a wild mix of weather this weekend and into next week. "It could still be a high impact... Oma or not, it does look like a high impact weather event occurs this weekend." Mr Noll said an "impressive storm system" moving up New Zealand from the south could merge with moisture from Cyclone Oma dropping down from the Pacific and Australia. "[It is] certainly not a time to let your guard down, there could be some heavy rain with that system, some high winds, maybe even high elevation snow in the South Island, and then temperatures that are more like a taste of late Autumn or early winter as we go into Sunday, Monday and Tuesday." When asked by Williams if that system could bring flooding and destruction similar to that which Cyclone Gita set down on New Zealand last year, Mr Noll said that was very possible. "The reason that could occur is because the soil right now is very dry, and that means it is kinda like concrete, so when the rain falls on that soil, that may just run off and not get absorbed by the ground," said Mr Noll. Mr Noll said eastern parts of the South Island, such as Christchurch up to Blenheim, and Wellington likely to be hit hardest by the storm, with South Island towns forecast to get a lot cooler very quickly. "They might struggle to get to 15degC as we go through Sunday into Monday and that is a massive change. Time to grab the jumpers." But that doesn't mean people in other centres are off the hook. "Everyone gets rain, everyone gets wind, everyone gets cooler," he said. WeatherWatch on Tuesday said the cooler change will begin on Friday with temperatures dropping significantly over the weekend. Regions like Southland and Canterbury can expect highs to reach only 14degC. Newshub.<doc-sep>Two large weather systems may merge over New Zealand later this week, bringing wild wind and heavy downpours of rain to northern regions. Meteorologists remain unable to predict whether Cyclone Oma, a category three cyclone currently moving past the northern tip of New Caledonia, will hit New Zealand. NIWA forecaster Chris Brandolino suggests there are two possible scenarios, with both ending with a likelihood of significant rain and wind for Aotearoa. "One scenario has [Cyclone Oma] going towards the Queensland coast, kind of just loitering out for the next several days, not really making it down to New Zealand," he told The AM Show on Tuesday. Mr Brandolino said, under that scenario some "moisture" from the cyclone will peel off and hit New Zealand's northern regions, with another incoming weather system adding to the wild weather. "That scenario also includes a separate weather system which comes Sunday or Monday, a southerly change. That brings some pretty good wind or rain for New Zealand". The second scenario would see Oma making its way to New Zealand and "merging with the aforementioned southerly change". That could create a massive weather system over the country, with Mr Brandolino saying the "atmospheric synergy" would produce something that was "greater than the sum of its parts". "You get a much larger system - either scenario is probably going to produce some pretty significant weather."<doc-sep>
If Tropical Cyclone Oma collides with New Zealand the destruction will be "devastating" and similar to that of Cyclones Fehi and Gita, MetService says. However, predictions are still unclear as to where the slow-moving system is tracking, and it will be another two days until forecasters can say with some certainty what will happen. Meteorologist William Nepe said the category two system was near New Caledonia at the moment, where winds were blowing at 92km/h. "There is still a great deal of uncertainty as to where it will track, it is at the moment slowing in the south-west, moving at about 6km an hour. "It could either go west towards Australia or it could come east towards New Zealand. "Some solutions have it moving towards New Zealand and recurving towards the north," Nepe said. "One thing we know with confidence is it will move slowly for the next few days." The power of the cyclone, if it hit New Zealand, would be similar to that of Cyclone Gita and Fehi which pounded the country last year. During Gita, Christchurch, Buller District, Grey District, Selwyn, Westland, Tasman and Taranaki declared a state of emergency as the country was bashed by 15m waves, more than 300mm of rain, and wind gusts above 130km/h. The cyclone should continue to move south-southwest during Wednesday and Thursday, to lie over the southern Coral Sea by the end of Thursday. Here's a look at the forecast wind gusts from Tropical #CycloneOma during the next 48 hours from NIWA's regional model 💨 Oma will track north of New Caledonia on Tuesday and move southward over open ocean on Wednesday-Thursday. pic.twitter.com/4f5gSezVv8 — NIWA Weather (@NiwaWeather) February 18, 2019 "I think it won't be until Thursday or Friday to know definitely," Nepe said. The system, as well as heavy rain and flooding, would come over the weekend at the same time there was potential for king tides. "That's if it were to become a deep low, it depends on what system we have interacting with it." "The worst-case scenarios are quite devastating, some of the model winds had 80-knot winds (158km/h) near the surface and 110 knots (203km/h) at several thousand feet. "It is quite alarming in the worst case scenario." Weatherwatch also confirmed the uncertainty of the tropical cyclone's path but could confirm that a new low forming around New Zealand would likely bring bouts of heavy rain. "This means a large new low with some connections to the tropics and cold air from the Southern Ocean will help produce a sizeable low-pressure system bringing rain to both islands. But where, how much and when still cannot be locked in due to so much chaos. "This is quite a complicated setup." The world "two most trusted sources" for cyclones were still at odds with the storm's path after Friday. "GFS [Global Forecast System] still picks the tropical low directly affecting New Zealand while ECMWF [European Centre for Medium-Range Weather Forecasts] shows Oma doing a complete U turn and reversing back into the tropics this weekend."