KEY POINTS:
Another sub-tropical storm is looking likely this Friday and Saturday and people should follow this one closely as it has the potential to cause damage. Flooding and, unlike last week's storm, also a significant risk of wind damage for some isolated pockets.
At the time of writing this the computer models were agreeing on a track that would see this low deepen quite quickly north of New Zealand during Friday then track down the centre of the North Island during Saturday. When I first saw the models for this system on Monday there was still a big question mark over this potential storm but as the week has progressed things have firmed up quite a bit. The usual disclaimer: as with any tropical system you need to keep up to date with forecasts and weather news frequently as these lows can be quite unpredictable.
Like last week we've set up a special storm link which you'll find here. We're going to be updating that link more frequently as the low approaches and deepens so definitely bookmark it and check back for updates.
The angle of this low is similar to a low that caused major wind damage and flooding across both islands last July. There are two pieces of good news associated with this low however.
Firstly, the rain bands are almost certainly going to deliver good rainfalls to parched farms along the North Island's east - such as Gisborne and Hawkes Bay. These places missed out on solid rain from ex-tropical cyclone Innis last week. The second piece of good news will be the speed of this low. It should clear the country in 48 hours meaning most severe weather shouldn't linger long. Its speed may also limit its intensity...if it moves over land faster it's unlikely to deepen as much which means winds will be weaker and less likely to cause serious damage.
Severe Gales
Eastern Waikato: Those in my home town of Te Aroha know all too well the damage severe easterlies can cause. Without a doubt this town gets hammered by easterlies worse than any other centre in New Zealand and last July's storm was the worst they'd seen in over 30 years with trees uprooted all over the place.
I went down there to see the damage and I had never seen anything like it. This predicted low isn't expected to be as bad but it definitely has the potential to cause damage...and with trees still heavy with summer leaves there's an increased chance of broken branches and trees being uprooted.
Western ranges along Taranaki, Horowhenua and Kapiti: Again in that July storm last year we saw a freak event that blew trees over mainly because the gale force winds came from an angle rarely experienced in these regions. Like I said about Te Aroha I'm not expecting conditions to be as severe but gales coming from the east across the region could damage trees affecting powerlines etc.
Heavy Rain
Eastern Northland, eastern Coromandel, Bay of Plenty and East Cape are my high risk picks for flooding and slips. Usually flooding rains occur in southern and eastern sides of a sub-tropical low, where the main frontal band is. Heavy rain may also cause problems in Hawkes Bay and potentially in Nelson or Marlborough. If you're driving anywhere over the Hawkes Bay, Gisborne or East Cape ranges watch out for rock falls.
This next system looks more unstable than Innis and possibly has more energy - also an increased chance of thunderstorms.
Remember these are all predictions and the weather is certainly chaotic and changeable at the moment...so please do check that link for updates and I'll have a full wrap here at nzherald.co.nz on Friday morning with an extensive look across the entire country for Friday, the weekend and then early next week.
Cold Snap
Forget Autumn arriving earlier in the South Island. Winter has arrived early instead. On Tuesday one word summed up weather in southern and eastern parts of the South Island - "miserable".
For weeks now from Kaikoura to Invercargill temperatures have been in the low to mid teens with just a few places climbing to 20 degrees now and then. On Tuesday at noon it was only around 10 or 11 degrees in Christchurch with some heavy showers about. Hardly the hottest month of the year.
From 40 degrees to 10 degrees in just a few weeks can't be pleasant. There is some good news...a low in the Tasman and this low in the sub-tropics should inject a bit of warmth back in the area with temperatures back into the late teens or early 20s. Still hardly the peak of summer.
The edge has really been taken off the daily highs lately. I drive with the air-con on all the time...a typical male who loves it to be arctic cold in my car at all times. But when I get home after work I no longer notice that thick wall of hot, humid, air when I step outside.
In fact the cool south westerly breeze lately has felt very similar to the inside of my car...not quite as arctic as the aircon of course but still not the same heat of previous weeks. This next sub-tropical low will make things sticky again in the north but there's absolutely no doubt in my mind now - I'm sorry to say it - but the heat has definitely peaked for Summer 08/09.
- Philip Duncan
