NZ Weather: MetService issues severe thunderstorm watch for Auckland, Northland, warns of hazardous driving conditions, flash flooding

People in Auckland and Northland should be prepared for bad weather on Wednesday with a severe thunderstorm watch issued.

MetService issued the watch for Wednesday afternoon and evening that could also see heavy rain.  

"Between about 1pm and 9pm today (Wednesday), a few of the thunderstorms could be severe about western and southern parts of Northland (south of Kaitaia), and about the broader Auckland region (including Waiheke Island), with localised downpours of 25-40mm/h," MetService said.

MetService warned that the "severe rain" could cause surface and flash flooding.

"Rainfall of this intensity can cause surface and/or flash flooding, especially in urban areas, and about low-lying areas such as streams, rivers or narrow valleys," MetService said. 

"It may also lead to slips. Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain."

MetService said wind gusts could get up to 60-70 kmph but the thunderstorm activity should ease and move offshore into the Hauraki Gulf on Wednesday evening. 

The severe thunderstorm watch comes after WeatherWatch said a tropical cyclone is expected to form in the Fiji/Vanuatu area in the coming week and could provide some much-needed rain to Kiwis that need it. 

"Long term and both GFS (American) and ECMWF (European) modelling show the tropical storm entering the Tasman Sea late January/February 1."