When it rains it pours...

Surface flooding in Hastings. Photo / Hawke's Bay Today

Our messy summer weather continues as we head in to what is typically the hottest and most settled month of all, February. But conditions were hardly settled over the North Island as January went out with a bang (literally) and February began with thunderstorms and torrential rain.

So what's causing the unsettled weather? Well last week thunderstorms were caused by unstable conditions over the North Island...basically moisture trapped over land and afternoon heating caused clouds to explode into thunderstorms. During the weekend, however, conditions changed and a low developed north east of East Cape. This then tapped into sub-tropical air south of Fiji and it was pulled down over the North Island. While this low was forming, a large high was developing just south of the South Island. The high is far more dominant and pushed back. This is why we're seeing settled weather over the South Island and such wet weather over the north. A complete flip of the weather from the summer weather so far.

And it's not just the weather patterns that have flipped. As the low developed east of Auckland yesterday something strange happened. With the low in the north east and the high in the south a strong easterly flow formed over much of the North Island...now that isn't strange but the low getting caught up in it was. Because almost all of our low pressure systems move in from the west...either the north west, west or south west. It is very rare to see a low over New Zealand track directly east to west...and then out in to the Tasman Sea towards Australia.

The high over the South Island is going to strengthen - this means a sunny, settled, week for those in central and southern areas and easterlies pretty much all week for the upper North Island.

So those along eastern parts of the South Island and in Southland - looks like settled summer weather has finally turned up for you. I predict hot weather for many places from Waikato southwards, especially western and inland areas. Perhaps more humid, cloudier weather in the north for Auckland and Northland.

The heavy rain over Northland today won't be a drought breaker... why? Two reasons: 1) Not all of Northland has received heavy rain. 2) It may be followed by a week of strong easterlies...drying the soil out again. It's time we start looking at the tropics and hoping for a sub-tropical low moving in from the northern Tasman Sea... that will be the drought breaker that is so desperately needed by Northland.