An intense convergence zone moved south-southeast through Northland into all areas of the upper North Island this morning. Frequent lightning. very heavy rain and flash flooding were the main features of the multicell cluster. A negatively tilted trough’ wedged itself between a warm and cold front which made the atmosphere ripe for severe thunderstorm potential. This type of low-pressure trough which accompanied a warm and cold front was invigorated by a powerful jet streak above it, and is notorious for producing severe weather conditions when they combine.
Widespread total between 50 to 150mm were experienced with a private rain gauge at Maungatapere just SW of Whangarei having 256mm within a few hours. Another notable total was 164mm just to the east of Kaiwaka.