Heavy rain, severe gales and thunderstorms: The weather's ramping up
Sunday, 20 May 2018
Heavy rain and widespread thunderstorms are on the way as a front sweeps up the country.
By mid morning Sunday, heavy rain and strong winds were battering the deep south in areas like Stewart Island, Fiordland and Milford Sound and the lower half of the South Island.
At the same time, thunderstorms were concentrated on the very south west of the South Island and around Stewart Island.
MetService duty meteorologist Angus Hines said the weather was 'still in the ramping up stage at the moment.
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'Most of the warnings and watches are sort of concentrated from this afternoon into the evening depending on where you are in the country.'
The wind was getting fairly strong around central New Zealand as well, he said.
'But that is also forecast to increase throughout the day today as well - so not really peaking until this evening for the more populated areas.
By mid-morning there was heavy rain falling in Fiordland and Milford Sound.
'We have a high risk of thunderstorms as well … we're forecasting a high risk of thunderstorms right up the West Coast of the South Island and the central South Island around the Southern Alps and spilling a little bit into the east as well.'
Road snow warnings were issued for the Lewis Pass, Crown Range, Milford Sound, Arthur's Pass and Lindis Pass for the 12 hours from 10am to 10pm Sunday.
'If people are planning to do things outside check the forecast as well as the warnings because we do have quite a number of watches and warnings out there at the moment, particularly for the South Island.'
MORE ON THE WAY
Although the weather was expected to ease on Monday, that wasn't the end of it.
'This current event will be pushing through tonight and tomorrow but the weather doesn't really relax right off, there's more severe weather waiting in the wings,' Hines said.
'We'll probably have a brief lull tomorrow and perhaps another bout of severe weather on Tuesday. It's actually a fairly similar weather situation on Tuesday.
'Similar places that are getting impacted this time will be affected again.'
The MetService severe weather outlook stated: 'On Monday, there is high confidence of severe west to northwest gales over Wellington and Wairarapa, and moderate confidence over southern parts of Hawkes Bay.'
Cold southerly outbreaks were expected to bring snow down to 500 metres over the lower South Island on Monday, but not in significant amounts.
On Tuesday and again on Thursday, very active fronts move up the South Island, and on both days there is moderate confidence of significant widespread rain in the west and severe northwest gales in the east.
SUNDAY IN DETAIL
According to the MetService severe weather warning, heavy rain and severe gale west to northwest winds for are expected for many parts of the South Island during Sunday and early Monday
'The heaviest rain is expected in Fiordland, Westland south of Otira and the headwaters of Canterbury and Otago lakes and rivers … Additionally, west to northwest winds are expected to reach severe gale in exposed parts of the Canterbury High Country and Canterbury Plains near the foothills, exposed parts of Marlborough, and in the North Island over Wellington and Wairarapa.'
It also said: 'thunderstorms are likely to produce heavy rain of 10 to 25mm per hour, small hail, strong wind gusts of 90 to 110 kmh or possibly more and there is even a slight risk of a small coastal tornado.
'A second front is forecast to move onto the lower South Island this evening,bringing a moderate risk of thunderstorms to Fiordland and coastal parts of Southland and Clutha. These thunderstorms are likely to produce localised heavy rain, small hail and strong wind gusts around 90 kmh.'
Heavy rain warnings:
- Westland south of Otira for 15 hours from 10am Sunday to 1am Monday.
- Forecast: Heavy rain with thunderstorms. In addition to rain that has already accumulated expect 120 to 140mm about the ranges, and 50 to 80mm near the coast. Peak intensities 15 to 25mm per hour in thunderstorms. Note that precipitation will be falling as snow above around 1600 metres.
- The headwaters of Canterbury and Otago lakes and rivers for 13 hours from 10am to 11pm Sunday.
- Forecast: In addition to rain that has already accumulated, expect 100 to 120mm about the Alps and 60 to 80mm within 30km east of the Alps. Peak intensities 15 to 25mm per hour in thunderstorms, mainly on the Divide. Note that precipitation will be falling as snow above around 1600 metres.
- Fiordland for 11 hours from 10am to 9pm Sunday.
- Forecast: Periods of heavy rain with thunderstorms. Expect 80 to 110mm in addition to rain that has already accumulated. Peak intensities of 15 to 25mm per hour in thunderstorms.
Strong wind warnings:
- Marlborough, Wellington and Wairarapa including the Tararua District for 20 hours from 3pm Sunday to 11am Monday.
- Forecast: Northwest gales are forecast to be severe at times, with damaging gusts of 140kmh in exposed places. The highest risk of severe gales is about and in the lee of the Kaikoura ranges and the Marlborough Sounds.
- Canterbury High Country and Canterbury Plains near the foothills for 15 hours from 10am Sunday to 1am Monday.
- Forecast: Northwest gales are forecast to be severe at times with gusts reaching 140 kmh in exposed places.