Tasman Tempest brings extremely heavy rain to New Zealand

Tasman Tempest brings extremely heavy rain to New Zealand

Parts of Northern New Zealand are being hit by extremely heavy rain as low over the Tasman Sea extends slow-moving fronts over the region. Rain is expected to continue through Sunday, March 12, 2017, but it will not be a steady rain, all week long. Some regions saw 100-year storms and their worst flooding in a generation.

Tasman low dubbed by NIWA meteorologists as Tasman Tempest brought heavy rain to the northeast of the North Island today, March 8, 2017 and periods of rain should continue over northern New Zealand through to Friday, meteorologists warned. The heaviest falls are likely to be in Auckland, the Coromandel Peninsula, Bay of Plenty and Gisborne north of Tolaga Bay, and a Heavy Rain Warning is now in place for these areas.

MetService warned that the initial burst of heavy rain is forecast to ease this afternoon, but further periods of rain are expected from Thursday to Sunday.

This weather system is expected to move slowly south across the Tasman Sea through Sunday, March 12, while an associated trough moves slowly down New Zealand from the north.

As of midday today (local time), Kawerau in northern Bay of Plenty had recorded an amazing 340.6 mm (13.4 inches) of rain since midnight. Similar extremely heavy falls were common across the eastern Coromandel, with Whangamata receiving 259.8 mm (10.2 inches) in less than 36 hours. That amount of rain is more than 150% of the normal rainfall for the entire month of Marc, NIWA meteorologist Ben Noll says.

The huge amount of rain that fell in Whangamata in 24 hours between 11:00 am on Tuesday and 11:00 am on Wednesday had a return frequency of 1 in 100 years. In that same 24 hour period, Waihi Beach recorded more than 220 mm (8.6 inches) of rain with a return frequency of 1 in 60 years.

Waiheke Island, just east of Auckland, woke up today to flooding, landslides and power cuts after receiving a month's worth of rain overnight. In Clevedon, residents are reporting huge stock losses as the town endures its worst floods in a generation. Two officers had to abandon their vehicle as it rapidly filled with water in Kawakawa Bay. The vehicle was then swept away in flood waters.

People were stranded in cars and residents were being evacuated in the cut-off Coromandel township of Whiritoa, Stuff reported.

It added that nearby Whangamata residents were left with no phones, petrol or wastewater after torrential rain continued to hammer the beachside town.

Flooding cut off access to the entire Coromandel Peninsula early on Wednesday morning after a night of downpours closed accessible roads. 

While rain across the Bay of Plenty is expected ease from tonight, significant additional rainfall (150+ mm / 5.9 inches) is expected across the eastern Coromandel as a very moist easterly flow continues to drive tropical downpours toward the Peninsula. Storm total rainfall, through the weekend, may exceed 500 mm (19.7 inches) in parts of the Coromandel.

Meanwhile, heavy rain will build back into Northland and northern Auckland from late tonight and continue through Friday. Additional rainfall in some locations may exceed 150 mm (5.9 inches), Mr. Noll says.

Another very heavy area of rain may move across most of the North Island, from north to south, from late Friday through Saturday and with it an increased risk for thunderstorms than may contain damaging wind gusts.

All the while, the Tasman Tempest will slowly move closer to New Zealand before possibly passing over the country on Sunday or Monday, causing more downpours.

The weather is expected to slowly settle across most of New Zealand by the middle stages of next week. By late week and into next weekend, high pressure may be the dominant weather player across the country, bringing plenty of dry weather and gradually warmer temperatures.

Warm and dry “beach-type” weather may actually be the flavor into late March as well: which will be much deserved after the extreme weather that Tasman Tempest brings.

Featured image credit: Tasman Tempest - low brings extremely heavy rain to parts of New Zealand. Credit: NASA/NOAA/DoD Suomi NPP / VIIRS. Acquired: March 7, 2017

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