TownsRuralMarineMtnsMaps

Thunderstorm Outlook

Valid to Midnight Thursday 17 Aug 2017
Issued at 8:17am Thursday 17 Aug 2017

A frontal rainband, preceded by a very strong northerly flow, will move eastwards over the northern South Island this morning and the North Island this afternoon and evening. Severe Weather Watches and Warnings are in force for heavy rain and northerly gales about central and southern New Zealand.

There is a low risk of thunderstorms associated with this front as it crosses Nelson, the Marlborough Sounds and western parts of the North Island from the Kapiti Coast up to Northland, as indicated on the chart.

Behind the front, an unstable showery northwesterly flow affects the South Island. In this northwest flow, there is a moderate to high risk of thunderstorms about Buller, Westland and Fiordland, especially from afternoon.These thunderstorms are expected to produce localised heavy rain of 10 to 20mm per hour and small hail.

There is also a low risk of a few thunderstorms spreading across the Main Divide into far western parts of Nelson, Canterbury, Otago and Southland, as well as coastal Southland and Clutha for a time this afternoon with a brief west to southwest wind change.

No other thunderstorms or significant convection expected over New Zealand during this time.

Valid to Noon Friday 18 Aug 2017
Issued at 10:13am Thursday 17 Aug 2017

A front is forecast to move slowly over Northland Friday morning and approach northern Auckland towards midday, bringing a low risk of thunderstorms to these areas.

Meanwhile, an unstable northerly flow over the South Island, brings further periods of rain or showers to the west. There is also a moderate risk of thunderstorms for Fiordland and Westland during this time. Any thunderstorms that occur are expected to produce localised heavy rain of 10 to 20mm per hour and small hail.

There is also a broader low risk of isolated thunderstorms over Buller, the Southern Alps, western parts of Southland and about Stewart Island, as indicated on the chart.

No other thunderstorms or significant convection expected over New Zealand during this time.

Valid to Midnight Friday 18 Aug 2017
Issued at 10:18am Thursday 17 Aug 2017

The front mentioned above crosses the northern North Island during Friday afternoon and evening to lie from Waikato to Bay of Plenty by midnight. There is a low risk of thunderstorms close to the front from about Waitomo, Taupo and Bay of Plenty northwards, as indicated on the chart.

Meanwhile, the unstable northerly flow over the South Island gradually eases during Friday afternoon and evening. There is however a moderate risk of thunderstorms about southern Westland and northern Fiordland during the afternoon, reducing to low in the evening. Any thunderstorms that occur are expected to produce localised heavy rain of 10 to 15mm per hour and small hail.

There is also a low risk of thunderstorms over remaining western areas from Buller to southern Fiordland, mainly during the afternoon.

No other thunderstorms or significant convection expected over New Zealand during this time.