Significant rain accumulations are expected in the Westland and Buller regions of New Zealand this week, prompting MetService to issue Red Warnings for Heavy Rain for the regions.
- Some locations might get as much as 2 to 4x their normal August rainfall.
Multiple fronts embedded within a strong moist northerly flow will affect New Zealand through to Sunday, August 21, 2022, bringing periods of heavy rain and gales to the northern and western parts of both islands.
There is high confidence of rainfall amounts reaching warning criteria in the northwest part of Marlborough, Tasman and Nelson, Buller and Westland on Thursday and Saturday, but low confidence on Friday, and moderate just for Buller and Westland on Sunday.
“An extended period of persistent, heavy rain is likely to cause major disruption around northern and western parts of the South Island,” MetService meteorologist Lewis Ferris said.1
“The ranges of Buller and Westland could see 350 – 600 mm [13.8 – 23.6 inches) of rain over a 56-hour period ending Thursday afternoon/evening. Areas will likely exceed their total average August rainfall during this period.”
The Tasman Ranges could see even larger accumulations of rain and are currently under an Orange Warning but there is still potential for an upgrade to a Red Warning for this area.
“Even if river levels are currently normal, the intensity of rain to come will mean these quickly rise and extreme caution is advised. Delays on the roading network are also to be expected. Closer to the coast the highest risk of flooding comes when the tides are high. Communities are at risk of being isolated,” adds Ferris.
Rainfall rates are forecast to peak on Wednesday, August 17 but the rain lingers into Thursday. There is a brief respite on Friday, however, rain looks to return by the end of the day and bring further rain into the weekend.
Residents living in the affected regions are urged to keep up with the forecast and follow the advice of local authorities.
“While the biggest impacts are expected within the Red Warning area, bear in mind that surrounding regions will also need to be on alert as large amounts of rain falling near the mountain tops can cause rivers to rise in areas not under a Heavy Rain Warning. The rain is accompanied by a warmer than normal airmass which will likely lead to snowmelt which will further increase the water draining into rivers,” cautions Ferris.
Severe Weather Watches and Orange Warnings are also in force for Heavy Rain and Strong Winds around the North Island.
This is the eighth Red Warning MetService has issued since the colour-coded system was introduced in 2019.
MetService Red Warnings are reserved for the most disruptive weather events and are only issued after consultation with the local Regional Council and Civil Defence.
1 Red Warnings for Heavy Rain in Westland and Buller – August 16, 2022 – New Zealand MetSerive
Featured image credit: NIWA
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