KEY POINTS:
The roaring 40s will certainly earn their nickname this week as a very strong westerly flow kicks into gear.
Both Tuesday and Saturday are currently looking to be 'peak' windy days with winds rising to gale force - maybe even hurricane force - in some exposed areas. In fact during Sunday afternoon winds around Castlepoint (Southern tip of the North Island) reached 135km/h with gusts over 100km/h on the hills around Wellington and Cook Strait - a sampler as to what's on it way perhaps.
But there's no shortage of high pressure to the north, so a fairly sunny, dry, week is on the way for regions north of Central Plateau with that famous 'squeeze zone' between the northern highs and the southern lows forming between Hawkes Bay and Southland - in other words, it'll be very windy in those regions, particularly southern and eastern areas, as that nor'wester cranks up.
Isolated pockets may see temperatures pushing near 30, although most temperature gauges are placed at airports so don't reflect the true warmth for those in the towns and cities where the sun combined with concrete and metal adds to the heat.
With the Spring Equinox now here everyone will now agree that Spring most certainly has started and as we soon slip into October the real spring weather kicks in - with severe gales and thunderstorms becoming more frequent.
As you're probably aware I'm not a huge fan of long range forecasts, beyond 10 days or so, but I can explain the typical weather patterns we tend to experience in Spring - and this year we are in a neutral period. that means no La Nina and no El Nino. El Nino (which usually brings westerlies creating droughts in the east) La Nina (which usually brings wet weather and easterlies to the north) so Neutral means a "normal" weather set up.
What does 'normal' mean? Not a great deal! Not in Spring anyway. Weather in Spring is chaotic anyway, but with a neutral weather pattern it should mean the prevailing westerly will become the 'norm'. There also seems to be a substantial amount of high pressure over the northern Tasman Sea and northern New Zealand which is bringing mainly clear skies and light winds to the top half of the North Island. So what does all this mean for the rest of September and going into October? Well if we do receive 'normal' spring weather with our prevailing westerly this is the most likely set up for over the country:
Northland, Auckland, western Coromandel, Waikato, Central Plateau - lots of high pressure around so mainly dry skies. If those highs shift northwards you'll be exposed to stronger westerlies and maybe squally/thundery showers moving in from the Tasman when the next southern low moves through. Clear skies at night (thanks to the highs) may mean cooler evenings. (At this stage the next 10 days look quite sunny and dry though).
Eastern Coromandel, Bay of Plenty, Gisborne - sunny and warm thanks to westerlies and plenty of high air pressure. Unless there's a low from the sub-tropics any moisture will be held back to the western side of the ranges. Cold nights when those winds die down.
Hawkes Bay, Wairarapa, Wellington, entire South island East Coast also Nelson, Marlborough and Central Otago - westerlies mean dry, warm, even hot, weather. Highs reaching anywhere from 20 to maybe 30 in the right conditions. But a southerly change will bring a shock to the system with temperatures halving. Could be cloudier over the Otago region due to those big lows to the south.
Taranaki, Manawatu, Kapiti - windy and perhaps often cloudy. Taranaki is especially vulnerable to thunderstorms and squally weather moving in from the west.
West Coast - after a pretty good winter Spring could mean more westerlies rather than those sunny, warm, easterlies. So more rain, cloud, and lower temperatures are likely.
Southland - a mix of warm days and very cold ones. Warm northerlies switching to cold southerlies and back again mean a real 'mixed bag' of Spring weather is on the way!
Of course these are all generalisations and should be treated as such, but it gives you an idea as to what we might see.
Don't forget to check out the Daily Debrief at the Weather Watch Centre - we post the national highs between 4 and 5 pm each day so you don't have wait until the 6 o'clock news to see them. I'm sure there'll be some interesting ones this week. The highs are taken from weather stations at the airports so they may not be as high as some areas might be experiencing - but we'll post you any 'unofficial' temperatures when we get them too. Oh by the way, the difference between official and unofficial is not a lot - some private weather stations are highly accurate - but unfortunately some are not! Official ones are the ones used by the government but as I said, they're usually placed at airports which are exposed areas surrounded by grass or water...they might not accurately reflect what you might be feeling at your place or downtown.
Enjoy the windy week!
Philip Duncan
For the latest weather news keep up to date with The Radio Network's new Weather Watch Centre or the NZ Herald weather section.
