Cyclone Gabrielle still poses a very serious threat to NZ – but forecasters keep saying “not 100% locked in yet”. So what are forecasters specifically looking at for any possible slight change in tracking?

As we said earlier this week, the cyclone has a very clear track towards NZ, but once it reaches NZ then a high pressure zone to the east will help control movement. Also, the cyclone is going from a tropical cyclone to extra-tropical – this always makes precise tracking even harder because the storm is making it’s biggest change since it first was created.

“For those asking if the storm could miss NZ in any way, the only real chance for this to happen would be for the high east of the country to either significantly weaken, or to drift further away to the east” says WeatherWatch.co.nz forecaster Philip Duncan. “It’s been a long time since New Zealand weather forecasters have seen such extreme weather modelling for the upper North Island – this is why you’re hearing all forecasters talk about this serious set-up. But the reason we’re saying “path not 100% locked in yet” is due to that high to the east. A slight shift in that high pressure zone can make really dramatic differences to the tracking of the cyclone and therefore the severe weather that goes with it for NZ”.

You can have both the most serious storm northern NZ has faced since the 1990s – but still be unclear about precise tracking once it arrives here – and therefore who is worst impacted. That has been the case all week and remains that way as we go across Friday.

Modelling is consistent still that the North Island has plenty of severe weather risks. But the further north or east this storm possibly goes the better it will be for NZ.

On Thursday night some models have shifted Gabrielle’s tracking just a little further east – other models have not budged at all. This means the north and east of the North Island remain the most exposed to this storm but shows there is certainly still some ‘wiggle room’ for this powerful cyclone once it arrives here.

Our weather forecast data updates hourly but global modelling updates a couple times a day. So every 24 hours we all get a big refresh of the world’s best modelling and that shifts the tracking each day a little. This is why forecasters can have confidence of a very serious storm – but still not know specific tracking until we get even closer to the event.

Many New Zealanders will be hoping that this serious storm is allowed to move through faster and offshore – despite our serious concerns forecasters also want this to happen! The high pressure zone to the east is the main controlling feature for that to potentially occur – and if we see any glimmer of a silver lining we’ll be sure to let you know.

But at this stage, we’re still seeing plenty of severe weather risks from this storm.

WHY DID WE WRITE THIS STORY?
Due to so many people asking if it was possible the forecast storm could just miss NZ. We’re trying to share with the public what weather forecasters are looking at to make their decisions and public communications in the days ahead. The more you understand about it all (including the parts that change) then the more the warnings, watches, and news headlines will make more sense.

WHAT THE COMPUTER MODELS SAY AS OF 6:30am FRIDAY MORNING – not much change, but a very slight shift east by UKMO and ECMWF. This latest shift by some makes little difference in severe weather risks for NZ at this stage.

• WeatherWatch.co.nz / RuralWeather.co.nz
  

🚨🌀#BreakingNews: Cyclone Gabrielle is now a "Severe Category 3" storm, says BoM. pic.twitter.com/S2DlbGEdcy

— WeatherWatch.co.nz (@WeatherWatchNZ) February 9, 2023

• WeatherWatch.co.nz