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Air pressure tug of war over NZ

A battle of air pressure continues over New Zealand today and forecasters say this is just the beginning of at least two weeks of similar weather.

The severe gales over central and western New Zealand this week have been caused by the squash zone – the area on the weather map where the isobars bunch up between high and low pressure – this week it was caused by a low north west of Northland and a big high spreading on to the South Island.

During Thursday this high will swell and advance northwards, causing the wind and rain to retreat northwards  where they came from – but with much of the energy now sucked out of that low the wind, rain and showers should mostly fizzle out over Thursday and Friday.

On Saturday the high will mostly be in control bringing frosts to sheltered parts of the South Island and light winds and clearing skies to much of the North Island – only Northland is predicted to have a risk of showers on Saturday.

Image – the wind forecast for 6pm Sunday shows another sub-tropical low moving down bringing strong winds to northern NZ / Weathermap

However the tug of war between high and low air pressure isn’t over with a new sub-tropical low, born over the Coral Sea, deepening and pushing down towards northern New Zealand on Sunday.

At the same time the high over the country will retreat southwards allowing a new squash zone to move down over the Top Half of the North Island bringing strong, or building, north easterlies and showers or patchy rain by the end of the day or overnight and into Monday.

All the models uses indicate this low will track south into the Tasman Sea however if the high moves away faster than expected, or weakens, then this next low could track much closer to New Zealand potentially bringing more heavy, widespread, rain. forecasters believe that Taranaki, Nelson and the West Coast will be most exposed to heavy rain early next week from this next system, but that prediction doesn’t exclude the possibility of heavy rain reaching other areas.

Later next week yet another low is predicted to form north west of New Zealand bringing more rain to the Top Half. says this is the first significant change in our weather pattern since mid December 2010, and indicates that the weather of recent months, which was made up of extended dry spells followed by short, dramatic bursts of heavy rain, may now be over – with more days of rain expected in the coming weeks than in previous months.



Sam on 28/04/2011 8:32pm

From today’s Courier Mail (Brisbane):
quote –
A low building in the Coral Sea is generating huge swells off Brisbane, with 7m-plus waves recorded yesterday off North Stradbroke Island.
The weather bureau yesterday issued a coastal wind warning from Cape York to Cape Moreton in the south.
The low was expected to form over the central Coral Sea last night and move rapidly south. It was not expected to develop into a cyclone.”

A month ago this low would have turned into a cyclone and we would be waiting for it to hit NZ.

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