Issued by MetService
In Brief:
Monday
North Island, rain, easing to showers in the north and clearing elsewhere. South Island, rain in most places, clearing in the northeast and west. Snow may lower to 500 metres in the far southwest.

Tuesday
North Island, showers over the northern half and mainly fine elsewhere. South Island, rain in the south and rain returning in the east. Mainly fine elsewhere.

Wednesday
North Island, showers in most places, but mainly fine in the southwest. South Island, rain or showers in the south and east, clearing in the far south. Mainly fine elsewhere.

Chatham Islands
Cloud increasing on Monday with strong northeasterlies. Rain developing on Tuesday with strong easterlies. Drizzle on Wednesday.

In Full:
On Monday a deep low is expected to lie slow moving just west of New Zealand and a ridge to the south. There is a moderate risk that rain may reach warning amounts in the Bay of Plenty and Nelson in a northeasterly flow associated with the low. There is a moderate risk that a southeast flow between the low and the ridge to the south of the country could bring heavy rain, and heavy snow lower than 500 metres to the south of Fiordland and the southwest corner of Southland.
On Tuesday the low is expected to remain to the west of the country and gradually weaken. There is however a low risk that an easterly flow could bring heavy rain to the far east of Southland, the east of Otago and Canterbury as indicated on the map.

Looking at charts from Ogimet, the approaching low pressure system is deepening and there's a high to our east, basically blocking movement of this low which is shown tomorrow at around 982 hPa and stays put to our west all week (there's reasonably good agreement throughout with ECMWF charts which improves confidence).

So, it looks like it is going to produce some heavy rain across the top of the north island starting today (Sunday) with strong northeasterly winds and spreading down to just about all other areas on Monday - winds turning westerly for the north but still northeasterlies down the east coast regions, though the bottom of the south island will probably get southeasterlies for a time. Possibly even some snow for the West Coast ranges of the south island.
Likely to be wet for a lot of places on Tuesday too, mainly top half of the north island and from Christchurch south - but Nelson Marlborough and east coast of the north island may actually have some finer weather. Winds look to be easing too and shifting more northerly for the north island to easterlies way down south.

Probably showers still about on Wednesday, mainly on the east coasts, both north and south with easterly winds prevailing.  There's some snow possible again in the south island (the brown overlay on the charts).

Thursday and Friday's charts continue to show some rainfall likely in both islands, most likely showers - if you escape getting rain one day, you'll probably get it the next.

Attached is a compilation of midday charts left to right, for Monday, Tuesday and Wednesday (you may have to scroll across to see them all)

Update:
Issued by MetService 1:33pm Tuesday 31 Jul 2012

To Midnight Wednesday 1 Aug 2012

Northland, Auckland and Coromandel
Occasional rain today. Showers tomorrow, some heavy, with possible thunderstorms in Northland.
Waikato to Manawatu, including the Bay of Plenty and central high country
Mainly fine, but isolated showers today, and again in western Bay of Plenty tomorrow.
Gisborne
Remaining areas of rain clearing today, but returning tomorrow afternoon.
Hawkes Bay, Wairarapa, Wellington, Kapiti, Marlborough, and Canterbury
Periods of rain, with some heavy falls about the hills and ranges. Rain clearing from Kapiti and Wellington tomorrow, and easing elsewhere.
Nelson
Scattered rain developing this evening. Further rain tomorrow.
Buller, Westland and Fiordland
Mainly fine, but patchy rain about Buller and northern Westland at times.
Otago and Southland
Patchy rain, clearing inland tonight. Becoming mainly fine tomorrow, but drizzle lingering about the east coast.
Chatham Islands
Cloudy periods and a few light showers.

Thursday
North Island, periods of rain in the east and showers in most other places, but mainly fine in the southwest. South Island, morning rain clearing about Nelson and periods of rain about Marlborough and Canterbury, a few showers in eastern Otago. Mainly fine elsewhere.

Friday
North Island, periods of rain in the east and showers elsewhere. South Island, a few showers in Nelson and eastern Otago, and rain about Marlborough and Canterbury. Mainly fine elsewhere.

SEVERE WEATHER WATCH FOR COROMANDEL PENINSULA, BAY OF PLENTY ROTORUA,
GISBORNE, HAWKES BAY, WAIRARAPA, MARLBOROUGH, NELSON, CANTERBURY

ISSUED BY METSERVICE AT 0918hrs 01-Aug-2012

MODERATE TO HEAVY RAINFALLS TO CONTINUE OR DEVELOP IN MANY EASTERN
AREAS FROM COROMANDEL PENINSULA TO NORTH CANTERBURY INCLUDING EASTERN
NELSON

A deep, slow-moving low to the west of the North Island is directing
a moist easterly flow over the country. This flow is bringing, or
expected to bring, rain to many eastern places until the weekend.
A rainfall warning is in place for the hills and ranges between the
Napier-Taupo Road and Manawatu Gorge, eastern Marlborough and
Canterbury north of Cheviot. Moderate to heavy rainfalls are also
possible in other areas as detailed below.
In eastern Nelson significant rainfalls are possible today (Wednesday)
and tomorrow.
For Marlborough and North Canterbury, some heavy falls are possible
outside the warning area today and moderate rain may continue
throughout the areas during Thursday and possibly Friday.
Rain is expected to become heavier again in Gisborne, Hawkes Bay and
possibly Wairarapa this afternoon. Outside the area contained in the
warning significant falls are still possible until Friday or even
early Saturday.
For the Coromandel Peninsula and western Bay of Plenty, heavy falls
are possible in the ranges during Thursday and Friday.
In all these areas accumulations are likely to remain below warning
criteria (except where warnings are in force). However, 50 to 60mm
of rain may fall over any 24 hour period. Forecasters will watch
these areas and will issue warnings if necessary. Due to the rain
that has already fallen, people should remain wary around streams and
rivers and watch for surface flooding and are advised to keep up to
date with the latest forecasts and warnings.

The low that WeatherWatch.co.nz dubbed as "the eight day low" may, in fact, affect our weather for much of next week too - but in a different form.  As we predicted last Sunday the low is expected to remain in the Tasman Sea for around eight days.  The low started to weaken on Tuesday and will continue to do so right up until this Sunday and Monday.

However head weather analyst Philip Duncan says the low may not completely go away next week.  "There's no doubt that this low is going to slowly weaken and fall apart over the next five days, however a southerly change next week may well give it more energy and a secondary low may in fact form over or near the North Island around Tuesday and Wednesday of next week bringing even more rain".

Mr Duncan says the latest forecast backs up a prediction made by WeatherWatch.co.nz last month that the first half of August would be generally wetter and milder for many regions.  While daytime highs haven't been excessive lately, most overnight lows have been above average with frost free conditions for most areas this week - despite being the coldest point of the year.

Decent snow falls have also been noticeably absent from the central North Island ski fields.  WeatherWatch.co.nz says the long range forecast isn't hugely positive either with a lack of true southerlies.

Next week high pressure was likely in the north Tasman Sea - effectively cutting off the sub-tropical element that has contributed to recent flooding across the country.  However the high will be centred over Australia's interior - a long way from being able to protect New Zealand from more rain.

On top of this North Island low another weaker low is also being predicted by some models for the lower South Island around Friday of next week.

Long range computer guidance currently suggests a spring-like westerly may then form across New Zealand in 10 days time.  If this data is accurate that would see more rain for western New Zealand and windier, drier and warmer weather for eastern areas.


- WeatherWatch.co.nz
http://www.weatherwatch.co.nz/content/could-our-current-low-trigger-more-rain-next-week-all-signs-point-yes

Our 8 Day Low continues to spit out rounds of unsettled weather.

Rain will be found across many parts of the country today.  But today, the focus will be on the North Island.  Specifically, the eastern regions of the North Island.  Government forecaster MetService has issued Heavy Rain Warnings for Gisborne, Hawkes Bay and the hills and ranges of the Tararua District.

WeatherWatch.co.nz forecasters agree that heavy rain looks to be most likely in these areas, with the heaviest rainfall totals like to fall about Gisborne.  MetService estimates that 80-120mm could fall by this afternoon.  Localised amounts of 120 to 140mm are possible with peak intensities of 15-20mm per hour likely.

Heavy Rain Warnings are also up for the ranges of Nelson west of Motueka.  However, it’s likely that the threat for heavy rain here should end early this morning.

While heavy rain is not as likely, the potential for heavy rain exists about Bay of Plenty, Waikato, Coromandel Peninsula, Rotorua, Wairarapa and Marlborough.

Many of these same areas will run the risk for additional heavy rain on Saturday.  However, at this time it appears to be a fairly low risk.

By WeatherWatch Analyst Howard Joseph
http://www.weatherwatch.co.nz/content/heavy-rain-targets-eastern-ni