Former Tropical Cyclone Debbie dumped up to three times the normal April rainfall in three days in some places, NIWA says.
The government weather agency has dubbed Debbie's New Zealand visit as a "tropical torrent" and some of its numbers, with the help of the "Tasman tempest" in March, are helping set records.
"The tropical torrent that spread over New Zealand this week, produced up to three times the normal April rainfall for some locations in three days," forecaster Ben Noll said.
Tropical moisture was siphoned southward towards New Zealand by remnant energy from ex-Tropical Cyclone Debbie forming an "atmospheric river".
Atmospheric rivers wash over the country about 40 days per year and are associated with 48 per cent of the country's rainfall extremes.
DEBBIE DOUSES NEW ZEALAND:
- Mangere recorded exactly its normal April rainfall (84.6mm) in just 14 hours between Tuesday evening and Wednesday morning.
- Mangere is off to its wettest start to any calendar year on record (since 1959).
- Hamilton is off to its second wettest start to any calendar year on record (since 1907) with 537mm
- Whakatane on Tuesday had its wettest April day on record (since 1952) with 137mm
- Whangaparaoa, north of Auckland, observed 172mm between Tuesday and Wednesday mornings, or 2.4 times the normal April rainfall
- The peninsula has received 670mm since the start of the rain and is off to the wettest start to any calendar year on record (since 1946)
- Kaikoura observed 155mm from the torrent, or 2.8 times the normal rainfall for April.
- Akaroa received nearly three times the normal rainfall for April.
New Zealand can expect more rain next week as it was essentially stuck in a "meteorological traffic jam" with strong low pressure systems to the west and sweeping high pressure systems to the south and east, Mr Noll said.
"This may result in another round of heavy rain from about late Tuesday for the North Island and north and east of the South Island."
– With NZN