Metservice – severe weather warnings for NZ

Metservice has issued a number of severe weather warnings for the northern part of New Zealand today, 31 January 2023.

For the latest weather warning information for your area, visit the Metservice.com website.

Severe Thunderstorm Watch

• Area: Northland. Period: 16hrs from noon Tue, 31 Jan – 4am Wed, 1 Feb. Forecast: A front is expected to bring heavy rain to Northland during Tuesday and overnight into Wednesday, as detailed in the Heavy Rain Warning. There is a moderate risk of severe thunderstorms with this front, bringing localised downpours of 25 to 40 mm/h or possibly more. Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips. Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain. Expect thunderstorms to ease from the north Tuesday evening and overnight. Issued: 7:17pm Mon, 30 Jan. Next update: 10am Tue, 31 Jan.
  Note: A Severe Thunderstorm Watch means conditions are favourable for severe thunderstorms in and close to the watch area. People in these areas should be on the lookout for threatening weather conditions and monitor for possible Severe Thunderstorm Warnings. For information on preparing for and keeping safe during a storm, see the Civil Defence Get Ready website.

Severe Weather Warnings

Further heavy rain for northern New Zealand along with possible severe gale northeasterlies

A strong and humid northeast flow covers the North Island. Bursts of heavy rain and thunderstorms likely for a number of regions through into Thursday, especially with an embedded front that is forecast to move slowly southeastwards over northern New Zealand.

Red heavy rain warnings are in place for Northland, Auckland north of Orewa and Coromandel Peninsula.

Orange heavy rain warnings are in place for Auckland from Orewa southwards, Great Barrier Island and Bay of Plenty.

A watch for severe northeast gales is also in place for Northland and Auckland.

People are advised to keep up to date with the latest forecasts in case any changes are made, or further areas are added.

Heavy Rain Warning – Red

• Impact: This rain is expected to cause dangerous river conditions and significant flooding. Slips and floodwaters are likely to disrupt travel, making some roads impassable and possibly isolating communities. Area: Northland Period: 27hrs from 3am Tue, 31 Jan – 6am Wed, 1 Feb. Forecast: Expect 120 to 170 mm of rain in the north and east, with lesser amounts in the west. However, localised areas may receive 170 to 270 mm. Peak rates of 10 to 20 mm/h, mainly in the north and east, but localised areas may see 25 to 40 mm/h, or possibly more. Thunderstorms are also possible, and a Severe Thunderstorm Watch is also in force.
• Area: Auckland north of Orewa. Period: 15hrs from 4pm Tue, 31 Jan – 7am Wed, 1 Feb. Forecast: Expect 80 to 120 mm of rain. Peak rates of 10 to 20 mm/h, but localised areas may see downpours of 25 to 40 mm/h. Thunderstorms are also possible.
• Area: Coromandel Peninsula. Period: 21hrs from 7pm Tue, 31 Jan – 4pm Wed, 1 Feb. Forecast: Expect 100 to 140 mm of rain about the ranges, with lesser amounts about the coast. Peak rates of 15 to 25 mm/h, especially about the ranges, but localised areas may see downpours of 25 to 40 mm/h. Thunderstorms are also possible.

Heavy Rain Warning – Orange

• Impact: Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.
• Area: Auckland from Orewa southwards, and Great Barrier Island. Period: 15hrs from 6pm Tue, 31 Jan – 9am Wed, 1 Feb. Forecast: Expect 50 to 80 mm of rain, especially north of the Harbour Bridge. Peak rates of 10 to 20 mm/h, but localised areas may see downpours of 25 to 40 mm/h. Thunderstorms are also possible.
• Area: Bay of Plenty. Period: 24hrs from 3am Wed, 1 Feb – 3am Thu, 2 Feb. Forecast: Expect 100 to 150 mm of rain, with the largest amounts likely about inland areas west of Whakatane. Peak rates of 15 to 25 mm/h, mainly in the west of the region where localised areas may also see downpours of 25 to 40 mm/h. Thunderstorms are also possible.

Strong Wind Watch

• Area: Northland. Period: 21hrs from 9am Tue, 31 Jan – 6am Wed, 1 Feb. Forecast: Northeast winds may approach severe gale in exposed places.
• Area: Auckland. Period: 18hrs from 2pm Tue, 31 Jan – 8am Wed, 1 Feb. Forecast: Northeast winds may approach severe gale in exposed places.
• Issued: 8:52pm Mon, 30 Jan. Next update: 10am Tue, 31 Jan

Road Snowfall Warnings

No Road Snowfall Warnings in force.

For more about Road Snowfall Warnings click here.

Heavy Swell Warnings

No Heavy Swell Warning in force for the Wellington, Wairarapa, Kapiti and Porirua coasts.

Swell warnings are issued directly to regional authorities for other selected coasts but are not currently published here.

Weather Warning Criteria

Severe Thunderstorm Warning

In New Zealand, MetService classifies a thunderstorm as severe if one or more of the following criteria are met:

• Heavy rain from thunderstorms of 25mm/h or more.
• Large hail of 20mm diameter or more.
• Strong wind gusts from thunderstorms of 110km/h (60 knots) or more.
• Damaging tornadoes with wind speeds more than 116km/h (63 knots) – i.e. Fujita F1 or stronger.

Note: some tornadic systems such as funnel clouds, waterspouts and small land-based tornadoes are possible with thunderstorms that may not be classified as severe.

Severe Weather Warning

MetService will issue a Severe Weather Warning whenever there is an expectation that any of the following weather conditions will occur within the next 24 hours:

• Widespread* rainfall greater than 50mm within 6 hours or 100mm within 24 hours;
• Widespread* snowfall below 1000 metres on the North Island, South Canterbury or Otago – or below 500 metres elsewhere on the South Island with a snow depth of 10 centimetres within 6 hours or 25 centimetres within 24 hours;
• Widespread* severe gales with a minimum mean speed of 90km/h or frequent gusts exceeding 110km/h.

*”Widespread” means over an area of 1000 square kilometres or more.

Severe Weather Warnings are classified into one of two categories – Orange Warnings or Red Warnings – depending on the expected severity and impact of the event. The majority of warnings issued will be Orange Warnings, with Red Warnings reserved for only the most extreme weather events.

Severe Weather Watch

MetService will issue a Severe Weather Watch whenever there is an expectation that conditions may deteriorate to the thresholds specified for the issue of a Severe Weather Warning:

• After the next 24 hours but within 48-72 hours, or
• If there is a high level of uncertainty within the next 24 hours.

Road Snowfall Warning

MetService will issue a Road Snowfall Warning for Napier-Taupo Road (SH5), Desert Road (SH1), Remutaka Hill Road (SH2), Lewis Pass (SH7), Arthur’s Pass (SH73), Porters Pass (SH73), Haast Pass (SH6), Lindis Pass (SH8), Crown Range Road, Milford Road (SH94) or Dunedin to Waitati Highway (SH1) whenever there is a likelihood of snow settling on one or more of those roads within the next 24 hours.

Disclaimer: These warnings provide information regarding expected weather conditions. They contain no information about current road conditions or about the amount of snow currently lying on any road.

Heavy Swell Warning

MetService will publish a Heavy Swell Warning for the following areas whenever there is an expectation that any of the criteria will occur within the next 24-48 hours.

The Kapiti-Porirua coast from Otaki to Cape Terawhiti:

• Combined waves of significant height 4 metres or greater from the westerly quarter (NW-SW) are expected to occur.

The Wellington south coast from Cape Terawhiti to Turakirae Head:

• Swell of 4 metres or more with a period of 14 seconds or more (from the southerly quarter) coinciding with high tide.
• Or combined waves of 6 metres or more (from the southerly quarter) coinciding with high tide.

The Wairarapa coast from Turakirae Head to Maitakona:

• Swell of 4 metres or more with a period of 14 seconds or more, coinciding with high tide.
• Or significant combined waves of 6 metres or more coinciding with high-tide.

Swell warnings are issued for other selected parts of the New Zealand coast by arrangement with Regional Councils and do not currently appear on the MetService website.