NZ Weather Forum

MetService wrote:A front is expected to rapidly cross over the South Island and much of the North Island during Tuesday afternoon and evening. There is a general low risk that embedded thunderstorms will accompany the front as it passes over Westland and the northwest of the South Island in the afternoon and in the west of the North Island during the evening. There is now an added moderate risk of thunderstorms occurring over Auckland, Waikato, Taumarunui and northern Taranaki during the evening. These are likely to bring brief heavy rain in the 10-25mm/hr range and strong wind gusts.

Another front should be approaching Fiordland at night. There is a low risk of thunderstorms developing about the fiords at night. If the thunderstorms occur they are likely to be accompanied by localised heavy rainfall and strong wind gusts.

Elsewhere, no thunderstorms or significant convection expected.

Metservice wrote: A front is expected to move rapidly across the South Island and much of the North Island from the west today. There is generally a low risk of thunderstorms associated with this front as it crosses Westland, Buller and Nelson this afternoon and the Marlborough Sounds, Kapiti and western areas of the North Island from Whanganui to central Northland including western Bay of Plenty and the Coromandel Peninsula this evening. However, for Taranaki,Taumarunui, western Taupo, Waitomo, Waikato and southern Auckland the risk of thunderstorms is moderate this evening and tonight. If thunderstorms occur they are likely to be accompanied by strong wind gusts and localised heavy rain with intensities of 10 to 20mm per hour.

A second front should be approaching the far south tonight. There is a low risk of thunderstorms developing about coastal Fiordland tonight, bringing localised heavy rainfall and strong wind gusts.

No other areas of severe convection or thunderstorms are expected.

Metservice wrote: Issued at: 10:55am Tuesday 28 Oct 2014

During Wednesday morning a slow-moving front should lie over Northland, Auckland and northern Waikato. There is a moderate risk of thunderstorms during the morning associated with this front for Northland and Auckland, and a low risk for the Coromandel Peninsula and northern Waikato. These thunderstorms may produce localised heavy rainfalls with intensities of 10 to 25mm per hour.

Another, very active, front is expected to move north over the South Island during the morning. There is a high risk of thunderstorms with and behind this front spreading north to affect Fiordland, Westland, Buller and western areas of Southland, Otago and Canterbury. These thunderstorms are likely to bring localised heavy rain with intensities of 15 to 25mm per hour and strong wind gusts of 90 to 110 km/h. There is a low risk that some of these thunderstorms may be severe and contain small tornadoes. In Fiordland there is also a high risk of hail of 5 to 15mm diameter and a low risk that hail of bigger than 20mm diameter could fall.

Outside of the high risk area, there is a low risk that some thunderstorms could spread further east into Nelson, Canterbury, Otago and Southland.

No other areas of thunderstorms or severe convection are expected.

Metservice wrote: A front over the north of the South Island at midday on Wednesday should move over the North Island during the afternoon and evening. Meanwhile, a trough following this front should cross the South Island. These features are expected to bring showers and possible thunderstorms to western areas of both islands.

The highest risk of thunderstorms is during the afternoon and evening in Buller and northwest Nelson. There is also a moderate risk of thunderstorms for Westland and Fiordland during the afternoon, for the Marlborough Sounds, Kapiti Coast, Manawatu, Wanganui and Taranaki during the afternoon and evening, and for Northland to the central North Island high country in the evening. These thunderstorms are likely to bring localised heavy rain with intensities of 10 to 20mm per hour and strong wind gusts of 90 to 110 km/h. Hail is also possible for the South Island areas and from Taranaki to Kapiti. There is a low risk that some of these thunderstorms could spread further east.

During the afternoon a southerly change is expected to move over Southland and Otago. There is a moderate risk that thunderstorms could develop on this change over Southland and eastern Otago (including Dunedin). If these thunderstorms occur they are likely to bring localised heavy rain with intensities of 10 to 20mm per hour and hail. As the change moves into Canterbury during the evening there is a low risk of thunderstorms along the Canterbury Plains.

Issued at: 8:50pm Tuesday 28 Oct 2014

During Wednesday morning a slow-moving front should lie over Northland, Auckland and northern Waikato. There is a moderate risk of thunderstorms during the morning associated with this front for Northland and Auckland, and a low risk for the Coromandel Peninsula and northern Waikato. These thunderstorms may produce localised heavy rainfalls with intensities of 10 to 25mm per hour. There is an additional low risk over Northland and northern Auckland of one or two localised downpours giving 25-35mm/hr and an outside risk of a small tornado.

Another, very active, front is expected to move north over the South Island during the morning. There is a high risk of thunderstorms with and behind this front spreading north to affect Fiordland, Westland, Buller and western areas of Southland, Otago and Canterbury. These thunderstorms are likely to bring localised heavy rain with intensities of 15 to 25mm per hour and strong wind gusts of 90 to 110 km/h. There is now a moderate risk that some of these thunderstorms may be SEVERE and produce wind gusts of 110+km/hr and the odd damaging tornado, mainly about the coast. In Fiordland there is also a high risk of hail of 5 to 15mm diameter.

Outside of the high risk area, there is a low risk that some thunderstorms could spread further east into Nelson, inland Marlborough, Canterbury, Otago and Southland.

No other areas of thunderstorms or severe convection are expected.

Metservice wrote: A front over the north of the South Island at midday on Wednesday should move over the North Island during the afternoon and evening. Meanwhile, a trough following this front should cross the South Island. These features are expected to bring showers and thunderstorms to western areas of both islands.

The highest risk of thunderstorms is during the afternoon in Fiordland and Westland and during the afternoon and evening in Buller and northwest Nelson. There is also a moderate risk of thunderstorms for the Marlborough Sounds,Kapiti Coast, Manawatu, Wanganui and Taranaki during the afternoon and evening,and for Auckland to the central North Island high country in the evening. Over Northland the risk is low at night. These thunderstorms are likely to bring localised heavy rain with intensities of 10 to 20mm per hour and strong wind gusts of 90 to 110 km/h. Hail is also possible for the South Island areas and from Taranaki to Kapiti. There is a low risk that some of these thunderstorms could spread further east.

During the afternoon a southerly change is expected to move over Southland and Otago. There is a moderate risk that thunderstorms could develop on this change over Southland and eastern Otago (including Dunedin). If these thunderstorms occur they are likely to bring localised heavy rain with intensities of 10 to 20mm per hour and hail. As the change moves into Canterbury during the evening there is a low risk of thunderstorms over the Canterbury Plains.

No other areas of severe convection or thunderstorms are expected.