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Major Heavy Rain And Wind Event Heading For New Zealand

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Some alarming numbers in here! 500mm in 27 hours in the Alps. Winds may gust to 100mph in the capital city, and much worse in the mountains.

Forecast for Cook Strait, then Wellington Harbour:

Northwest 40 knots rising to northerly 50 knots tonight and to 65 knots early morning. Easing to northwest 35 knots late morning then changing southerly 45 knots Tuesday evening.

Tuesday: Northerly rising to 50 knots gusting 75 knots early morning. Easing to northwest 25 knots gusting 35 knots in the afternoon, changing southerly 30 knots gusting 45 knots in the evening.

http://m.metservice.com/warnings/swx

SEVERE WEATHER WARNING.

ISSUED BY MetService AT 9:32 am 27-Dec-2010

VERY HEAVY RAIN ABOUT THE SOUTH ISLAND WEST COAST, SOUTHERN ALPS AND OTAGO TODAY AND EARLY TOMORROW SPREADS TO THE CENTRAL AND SOUTHERN NORTH ISLAND ON TUESDAY SEVERE GALE NORTHERLIES ABOUT CENTRAL NEW ZEALAND ON TUESDAY

A cold front will lie slow-moving over the southern South Island today before sweeping quickly across the remainder of the country tomorrow.

A strong moist northwesterly flow ahead of this front will bring very heavy rain to the South Island west coast and the Southern Alps today and early tomorrow, and to central and southern parts of the North Island on Tuesday. Heaviest falls are expected about the Westland ranges where up to 500mm is forecast, with some exceptionally intense falls at times. Elsewhere between 200 and 300mm of rain is forecast for parts of Buller, Nelson, the Tararua ranges, Mt Taranaki, and also the headwaters of the Canterbury and Otago rivers. Other areas which can expect heavy rain during the next couple of days include Otago, Marlborough, Wellington, the central North Island, and the ranges of eastern Bay of Plenty. This heavy rain will cause river and stream levels to rise rapidly, and there may be slips, surface flooding and poor visibility making driving conditions hazardous.

North to northwesterly winds are also expected to reach severe gale about many parts of central New Zealand for a time on Tuesday, with the strongest winds near Cook Strait where gusts may reach 160km/hr. Gusts of 120km/hr or higher can also be expected elsewhere from Taupo to North Canterbury. Gusts of this strength could cause damage to trees, powerlines and insecure buildings, as well as make driving conditions hazardous especially for motorcyclists and high sided vehicles.

This is a very significant event with heavy rain and severe gales affecting many areas. People across all of New Zealand could be affected, and everyone is advised to keep up to date with the latest forecasts and warnings.

HEAVY RAIN WARNING

AREA/S AFFECTED

Fiordland

FORECAST

Periods of heavy rain are expected today. In the 12 hours from 9am to 9pm today (Monday), 60-80mm are likely, mainly north of George Sound.

FREEZING LEVEL: About 2800 metres.

AREA/S AFFECTED

Westland south of Franz Josef.

FORECAST

Rain is expected to become heavier today. In the 24 hours from 9am Monday to 9am Tuesday, 200-250mm of rain is expected about the ranges. Heaviest falls should today, with rainfall rates of 20-30mm/hr.

FREEZING LEVEL: About 3000 metres.

AREA/S AFFECTED

Westland north of Franz Josef

FORECAST

Periods of very heavy rain are expected today and tomorrow morning. In the 27 hours from 9am today (Monday) to midday Tuesday, 300-500mm of rain is expected about the ranges, and up to 200mm near the coast. Some exceptional intensities are likely, with rainfall rates reaching 30-50mm/hr at times.

FREEZING LEVEL: Above 3000 metres.

AREA/S AFFECTED

Otago

FORECAST

1. Heavy rain is expected about the main divide of the Southern Alps today and tomorrow morning. In the 24 hours from 9am today (Monday) to 9am Tuesday, 150-200mm of rain is expected near the main divide, with about 100mm spilling over to within 10km east of the divide. Intensities reaching 20-30mm/hr at times. The greatest accumulations will be north of Lake Wakatipu.

2. Over remaining parts of Otago, widespread rain is expected to develop this afternoon and evening in a cooler southerly flow, and continue through to Tuesday afternoon. In the 24 hours from midday Monday to midday Tuesday, 75-100mm of rain may accumulate in some places. Heaviest falls are likely north of Dunedin and Alexandra.

FREEZING LEVEL: About 3000 metres.

AREA/S AFFECTED

Headwaters of the main Canterbury lakes and rivers.

FORECAST

Heavy rain is expected today and tomorrow morning. In the 27 hours from 9am today (Monday) to midday Tuesday, 250-350mm of rain is expected near the main divide, and up to 150mm spilling over to 15km east of the divide. Maximum intensities of 30-40mm/hr from Monday evening.

FREEZING LEVEL: Above 3000 metres.

AREA/S AFFECTED

Buller

FORECAST

Rain is expected to become heavier today. In the 30 hours from 9am today (Monday) to 3pm Tuesday, 200-300mm of rain is expected, particularly about the ranges. Heaviest falls overnight when rainfall rates may reach 30-40mm/hr.

FREEZING LEVEL: About 3000 metres.

AREA/S AFFECTED

Nelson

FORECAST

Heavy rain is expected to develop this evening. In the 16 hours from 6pm today (Monday) to 10am Tuesday, expect 200-300mm of rain about the ranges of Northwest Nelson, and up to 100mm elsewhere especially near the Bryant ranges. Intensities may reach 20-30mm/hr overnight.

AREA/S AFFECTED

Marlborough

FORECAST

Periods of heavy rain are expected on Tuesday morning. In the 12 hours from midnight tonight (Monday) to midday Tuesday, expect 100-150mm about the Richmond ranges and Marlborough Sounds, and 60-80mm elsewhere in Marlborough.

AREA/S AFFECTED

Wellington and the Kapiti Coast

FORECAST

A period of heavy rain is expected on Tuesday morning. In the 9 hours from 3am to midday Tuesday, 60-80mm of rain is likely, with rainfall rates reaching 10-15mm/hr at times.

AREA/S AFFECTED

Tararua Range

FORECAST

Heavy rain is expected on Tuesday. In the 15 hours from midnight to 3pm Tuesday, 200-300mm is expected, mainly about the southern Tararuas.

AREA/S AFFECTED

Taranaki

FORECAST

Heavy rain is expected on Tuesday. In the 15 hours from midnight to 3pm Tuesday, 200-300mm of rain is expected on Mt Taranaki, and 60-80mm elsewhere (mainly north and east of the mountain). Rainfall rates may reach 30-40mm/hr on the mountain.

AREA/S AFFECTED

The central North Island high country from Te Kuiti to Tongariro National Park.

FORECAST

Heavy rain is expected on Tuesday. In the 12 hours between 4am and 4pm Tuesday, expect up to 200mm about the mountains of Tongariro National Park, and 60-80mm elsewhere.

AREA/S AFFECTED

The ranges of eastern Bay of Plenty (east of Kawerau)

FORECAST

Periods of heavy rain are expected on Tuesday. In the 15 hours between 6am and 9pm Tuesday, up to 100mm of rain is likely.

STRONG WIND WARNING

AREA/S AFFECTED

Marlborough, excluding the Sounds

FORECAST

North to northwest winds are expected to reach gale in exposed places from late this evening through to about mid-morning Tuesday, with possible gusts of 130km/hr.

AREA/S AFFECTED

Wellington and the Marlborough Sounds

FORECAST

Northerly gales are expected to become severe in places from later this evening, with damaging gusts of around 160km/hr likely through to around midday Tuesday.

AREA/S AFFECTED

Wairarapa

FORECAST

North to northwest winds are expected to rise to gale overnight, with gusts of 150km/hr possible through to early Tuesday afternoon.

AREA/S AFFECTED

The central and lower North Island from Taranaki to Taupo down to Kapiti.

FORECAST

Northerly winds are expected to rise to gale in exposed places overnight Monday peaking in the morning before easeing from the west early afternoon. Gusts of 120km/hr are likely in exposed places and gusts of 150km/h are possible about higher terrain, especially around the Central Plateau.

AREA/S AFFECTED

Gisborne and Hawkes Bay

FORECAST

North to northwest gales are expected to develop about exposed places early Tuesday morning and should ease late afternoon. Gusts of 130km/hr are possible in exposed places during this time, especially near the ranges.

AREA/S AFFECTED

Inland North Canterbury

FORECAST

North to northwest winds are expected to reach gale in exposed places from this evening through to early Tuesday morning, with possible gusts of 120km/hr, especially near the foothills.

NEXT SEVERE WEATHER WARNING WILL BE ISSUED AT OR BEFORE 9:00 pm Monday 27-Dec-2010

Forecast prepared by: John Crouch and Andy Downs

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Wellington Airport TAF:

TAF AMD NZWN 270019Z 2700/2724 35025G35KT 9999 -DZ BKN020

BECMG 2706/2708 35040G55KT

TEMPO 2712/2724 4000 RA BKN008

BECMG 2714/2716 35055G70KT

BECMG 2720/2722 34040G55KT

BECMG 2722/2724 34025G35KT =

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Wow ...this is going to disrupt a lot of people, especially with it being the holiday season!

I can see a lot of camping and tramping trips being washed/blown out not to mention the travel disruption!

(No mention of the weather when I spoke to my family yesterday.... but I don't see Northland in the affected areas.)

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It turned out quite serious for much of the country south of the Central Plateau. Wellington hilltops managed a gust of 107mph. NIWA summarise it in their monthly report here:

http://www.niwa.co.n...r2010_FINAL.pdf

It was an exceptionally warm December, although the national high of 33C is not particularly extreme (it was lower by 0.1C than Novembers extreme maximum).

For rainfall, Mt Cook Village got over 300mm in 24 hours during that event (even though it's east of the Divide). So it seems reasonable that some mountain locations did get 500mm.

Not sure what the annual totals are, but on 25th December: http://www.nzherald....jectid=10695809

It always amuses me, this contrast, given that Clyde and Milford Sound are about 60 miles apart yet manage a huge x20 factor in their rainfall pretty much every year.

"The most rainfall so far for year, not surprisingly, is Milford Sound," Ms Griffiths said.

Latest figures from NIWA measured 6152mm (just over 6 metres) of rain in the area.

The driest area was in central Otago, which Ms Griffiths said was not unusual. Clyde, the driest spot in the country, received no more than 319 mm for the year.

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