Updated 3:55pm from Weather Watch. Is she changing direction? The exact path of Lusi over New Zealand this weekend remains unclear with computer modelling continually shifting the future track of the storm westwards.
This afternoon Lusi's wind speeds have ramped up further, according to JTWC, with winds averaging
130km/h and gusting to 160km/h. Fiji Met says the air pressure has now fallen to
960hPa.In the past 24 hours most reliable data has suggested the centre of the tropical low might now push west of Northland and Auckland on Saturday night/Sunday morning.
The latest data also suggests the centre of the low might track further south into the South Island now - bringing more rain and wind into the upper South Island and potentially Canterbury."For the working week so far the data has suggested the low would track across the North Island or along the western coastline of the North Island. Today we're seeing the high east of New Zealand pushing back a bit - helping the low sink further southwards down the South Island" says head weather analyst Philip Duncan.
"We'll need to see another 12 to 24 hours of computer runs to be certain of this developing change in the predicted track".
Mr Duncan says the high east of New Zealand is acting as leverage - helping tilt the air pressure and that shifts the direction of the low.
WeatherWatch.co.nz says the shift in tracking will still see Northland, Auckland, Coromandel and Waikato exposed to the full brunt of the storm - which will be weakening upon arrival. Two data updates today have weakened the low a little upon arrival - however there would need to be further similar updates before that could be locked in.
However Fiji Met has today release a new threat map which shows the storm retaining Cat 2 status all the way to the South Island - something rarely seen.Many farmers are wanting the rain to arrive with near-drought conditions forming in some North Isand areas. To have the low weaken before landfall would be a positive outcome, reducing wind damage risks but still maintaining soaking rains for many areas.
In Auckland winds are likely to ramp up as Saturday ticks along. Gales are expected to develop with the risk of severe gales in the afternoon or evening - and overnight. If the low tracks further west than predicted it may not mean any easing in winds - instead it will change the wind direction away from ESE to more NE.
Rain may also be patchy - although patchy doesn't mean light and drizzly. Some rain data suggests torrential downpours in the mix with lighter falls.
"My feeling is that this low is quite complex and we may not have a truly clear picture until Saturday, at least rainwise"
The geography across the country means the wind and rain could be severe in a number of places. "Everytime the models shift the track of the low it means all the forecasts also change - especially wind direction, which is key to working out severe gales and where highest rainfall accumulations will be".
With the low now possibly tracking further south over the South Island places like Dunedin may now have more wind and rain - along with Canterbury, Nelson and Marlborough.
"Originally it looked as though the low would take the offramp at Cook Strait to depart our shores, now it looks as though it might turn off further down the road over Canterbury and Otago".
Mr Duncan says the best advice to people is that this weekend, for many parts of the country, there will be wet and windy weather for a time "Not everyone will have severe weather or damage - but this storm is complicated and brings with it high risks for severe weather to various parts of the country".
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February 21, 2012, 05:22:31 PM
