Updated 3:24pm — Cyclone Winston is no longer ‘severe’, after dropping another category overnight down to a Category 2 tropical cyclone, out at sea, directly to the north of New Zealand. Winston is slowly weakening and WeatherWatch.co.nz believes it will be a strong Category 1 cyclone by tonight or overnight.
The cyclone had a central air pressure reading of 970hPa this morning, up from 960hPa on Tuesday and 915hPa on Saturday at its peak. Now it’s risen a bit further to 975hPa.
As a result of the air pressure rising, the winds have fallen. Sustained winds have fallen from hurricane force (120km/h) to 100km/h now and gusts to 130km/h or so.
Winston continues to gain speed as it leaves the tropics – travelling S yesterday at 5km/h, then SSE at 15km/h this morning – and this afternoon it’s racing along at 24km/h to the SSE. It will today continue south, before tomorrow and Friday swinging south west and out into the north Tasman Sea.
The Fiji Met Service, which says on its website it’s both a Cat 2 and Cat 3 storm (currently a weak Cat 2 storm), has managed to update its forecast track – and in their more recent update the future track of Winston is likely to be very close to Norfolk Island – and may even make a direct hit .
The small island, home to just over 2000 people, may see the centre of Winston pass closely by on Thursday night or Friday as a Category 1 cyclone, or close to it. Winston will likely lose its tropical cyclone status on Thursday or Friday.
WILL WINSTON HIT NZ?
It’s the million dollar question that we still can’t answer with certainty. At this stage we do not expect New Zealand to be hit by a tropical cyclone, with Winston weakening significantly this week. But the remnants may still produce severe weather – and in particular, heavy tropical rain.
But the computer models – which have been perfect at nailing the rest of the weather map – are struggling with Winston to levels we have rarely seen before. While yesterday the two main models we trust out of Europe and the US were finally in agreement – Winston would create new rain bands over the North Island this weekend, then the low would weaken and unravel over the North Island on Monday and Tuesday – today, they are not.
Today, the US model still says that – while the European model says perhaps Winston will float over to Australia. Three days ago it was the reverse – the US model thought Winston might not only end up in eastern Australia and the Coral Sea – but the ex-cyclone might then track NW towards Papua New Guinea while the European model picked the low would entirely unravel around the upper North Island.
Why the confusion? It’s all to do with high pressure over the North Island and central New Zealand. Cyclones and tropical lows avoid highs – in facts highs can tear them apart. So this low is meandering around the northern fringes of this belt of high pressure, looking for the path of least resistance. As we saw 10 days ago the high east of New Zealand ballooned in size and that guided Winston back into the tropics towards Tonga. While not common, this does sometimes happen – but Winston is proving to be a particularly stubborn storm that cannot ‘escape’ the tropics due to blocking highs to the south – around New Zealand.
For Winston to hit New Zealand as a tropical low we need a gap in that high air pressure – and this is what the models appear to be conflicted on – just how big and strong the high will be over New Zealand, and how that might guide or affect Winston’s remnants.
The modelling and data we trust at WeatherWatch.co.nz has been a little more sure of itself this week – but today it has undone some of that. In other words – we still need to ‘watch this space’ – and we feel that by Friday we’ll have a pretty good handle on what is going to happen. At least for now, no tropical storm is directly coming to New Zealand – but the remnants of Winston will absolutely be something to watch until the low has finally moved away – which could be another week at the latest.
Latest track map from Fiji Met
Track map via JTWC
Winston’s current placement – halfway between New Caledonia and Tonga, well out at sea, and well SW of Fiji, and well SE of Vanuatu – tracking SSE today, then S to SW overnight tonight. / WEATHERMAP