MetService Thunderstorm Outlook
Valid to: Noon Sunday 8 Dec 2019
Issued at: 5:52am Sunday 8 Dec 2019
Chart updated to increase risk to high over central New Zealand and issue SEVERE THUNDERSTORM WATCH.
A front embedded within a very humid northwest flow is expected to become slow moving over central New Zealand Sunday morning. A high risk of thunderstorms is in place from Waitomo and Taihape to Wellington, Nelson and Marlborough, and a SEVERE THUNDERSTORM WATCH has now been issued for this area, with rainfall intensities of 25-40 mm/h there. Strong wind gusts are also possible, between 90-110 km/h. Refer to the latest severe weather watches and warnings for more info.
A moist unstable northwest flow affects the North Island. There is a general low risk of thunderstorms from Northland the the central high country and the Bay of Plenty, but the risk rises to moderate towards noon in the south of Northland, Auckland, Coromandel Peninsula, Waikato, Waitomo, Taumarunui, Taupo, Bay of Plenty and Rotorua. These storms may be accompanied by heavy rain, 10 to 15mm per hour and strong wind gusts, 90 km/h.
The South Island is affected by unstable northwesterlies and there is a moderate risk of thunderstorms in Buller, Westland, Fiordland and the west of Stewart Island. These storms may be accompanied by hail, strong wind gusts, 90 to 100 km/h and heavy rain, 10 to 25mm per hour. There is a low risk of thunderstorms affecting much of the remainder of the South Island apart from the Canterbury Plains and the south of Marlborough.
No thunderstorms or significant convection expected elsewhere.
MetService T-storm Outlook Map for Dec 08 am, Is. 5.50am.png
Valid to: Midnight Sunday 8 Dec 2019
Issued at: 6:29am Sunday 8 Dec 2019
The front is expected to move slowly northeast over the North Island during the remainder of the day. This front and the moist unstable airmass ahead of it brings thunderstorms and possible severe thunderstorms to many areas, including downpours (rainfall intensities of 25-40 mm/h), and possible small tornadoes in Taranaki during the afternoon and evening.
The combination of afternoon heating and a very humid air mass is expected to create conditions favourable to afternoon and evening thunderstorms across large parts of inland North Island. There is a high risk of thunderstorms from Northland to Taranaki, the central North Island high country, Coromandel Peninsula and the Bay of Plenty. Horowhenua and Kapiti Coast are also affected. These storms may be accompanied by heavy rain, 10 to 25mm per hour, 10 to 20mm diameter hail and strong winds gusts, 90 to 100 km/h. There is a low risk that some of these thunderstorms may be severe with downpours, 25 to 40mm per hour and hail larger than 20mm.
During the afternoon there is a moderate risk of thunderstorms in the Marlborough Sounds, Wellington, Wanganui, Manawatu, the north of Wairarapa and the south of Taihape as indicated on the chart. These storms may be accompanied by heavy rain, 10 to 25mm per hour and strong wind gusts. 90 to 100 km/h.
A cold upper trough expected to move over the lower South Island during Sunday afternoon and evening brings a general moderate risk of thunderstorms to many areas, from southern Buller to Fiordland, and extending into Southland, Otago and Canterbury. Rainfall intensities of 10-20 mm/h and hail of 15 mm or less are expected with these thunderstorms.
A low risk of severe thunderstorms is also in place for Dunedin, North Otago, Canterbury Plains and Christchurch (late in the day) as the front coupled with the upper trough is expected to move through. Heavy rain of 10-25 mm/h, large hail with diameters 20 mm or more and small tornadoes are possible.
A low risk of thunderstorms covers most other areas as indicated on the chart.
MetService T-storm Outlook Map for Dec 08 pm, Is. 6.28am.png
