A Tasman low moved across the Tasman during the last few days and became stationary to the west of Auckland on Sunday 29th August. This made for a stormy Sunday across the upper North Island with many multicell cluster electrical storms observed during the afternoon.
On Monday 30th August the low inched closer and became a significant risk for substantial rainfall for late in the day as suggested in our social media post in the morning. By sunset the upper atmosphere was abnormally cold which triggered significant instability and a severe convergence zone of storms from the Kaipara Harbour to the Hibiscus Coast.
These storms were moving slowly southward towards Auckland.
Seeing the potential danger of the intense rain, we did a new social media post at 7:33pm to give people a heads up. As per the NZ severe weather code of conduct, all official warnings are issued by MetService.
Large hail was part of this line of storm as seen here around Helensville.
The line of intense rain and storms slowly moved south and became stationary from the Gulf to the Waitakere Ranges dropping 100 to 230mm of rain within 14 hours.
By afternoon the low started moving North leaving behind a trail of destruction.
