Today's torrential rain is a "weather traffic jam", not unlike an Auckland morning during March Madness, says Niwa meteorologist Ben Noll.
It's an autumn trifecta for weather-induced misery: strong and slowing moving low pressure, deep tropical moisture, and a blocking ridge of high pressure to the south.
The strong and slow moving low pressure is the driving force behind all of the adverse weather.
The deep tropical moisture is an atmospheric moisture source from the Indian Ocean, Coral Sea, and Pacific Islands, known as an atmospheric river.
And the blocking ridge of high pressure is high pressure building to the south and east of New Zealand, encouraging slow movement of the "Tasman Tempest", effectively preventing it from moving over the next several days, says Noll.
