Thunderstorm Outlook
Issued at 7:47am 26/04/2025
Valid from 7:47am 26/04/2025 to Midnight 26/04/2025
A slow-moving front lies to the northwest of the North Island. This front directs a moist northwest flow over northern New Zealand. During the day a low risk of thunderstorms slowly spreads south over Northland, Auckland and northern Coromandel Peninsula. From this afternoon, the risk of thunderstorms becomes moderate in the far north of Northland, north of Kaitaia to Bay of Islands, and localised heavy rain with intensities of 10 to 25 mm per hour are possible. Tonight, there is moderate risk of downpours of 25 to 40 mm per hour regardless of whether thunderstorms occur or not. This evening and tonight the moderate risk of thunderstorms spreads south over Northland, to reach Dargaville to Whangarei around midnight. These thunderstorms may bring localised heavy rain with intensities of 10 to 25 mm per hour and tonight there is a low risk of downpours of 25 to 40 mm per hour. No other areas of severe convection or thunderstorms are expected.
Issued at 10:11am 26/04/2025
Valid from Midnight 26/04/2025 to Midday 27/04/2025
A slow-moving front lies over, or near, Northland during the day. Another front approaches the south of the South Island. There is a low risk of thunderstorms about Northland and northern Auckland that spreads south to cover the rest of Auckland, the Coromandel Peninsula and western Waikato during the morning. For Northland, north of Dargaville to Whangarei, there is a moderate risk of thunderstorms. These thunderstorms may bring localised heavy rain with intensities of 10 to 25 mm per hour and there is a moderate risk of localised downpours as well with intensities of 25 to 40 mm per hour. For the rest of Northland and northern Auckland, the risk of thunderstorms also rises to moderate during the morning. Localised heavy rain with intensities of 10 to 25 mm per hour is possible, and there is a low risk of downpours of 25 to 40 mm per hour. There is also a low risk of thunderstorms about Fiordland. No other areas of severe convection or thunderstorms are expected.
Severe Thunderstorm Criteria
In New Zealand, MetService classifies a thunderstorm as severe if one or more of the following criteria are met:
Heavy rain (from thunderstorms):
Rainfall of 25mm/h, or more.
Large hail:
Hailstones 20mm in diameter, or larger.
Strong wind gusts (from thunderstorms):
Gusts of 110km/h (60 knots) or stronger.
Damaging tornadoes:
Fujita F1 - i.e. wind speeds greater than 116km/h (63 knots) 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.
