After thrashing Australia, what’s left of ex-Tropical Cyclone Debbie is forecast to slowly move across the Tasman Sea over the weekend and soak New Zealand next week.
NIWA forecaster Ben Noll says the remnant energy from the storm will work with a Tasman Sea frontal boundary to bring downpours, possibly causing flooding across the country.
“Heavy rain will become likely for parts of the central and lower North Island from late Monday, reaching a peak on Tuesday before sliding toward the South Island on Wednesday,” he says.
Noll says the storm will both be slow to approach and depart next week because a strong area of blocking high pressure –in the shape of a banana– will stretch from Tasmania to the southern Tasman Sea and to the east of New Zealand.
“Tropical moisture from the Coral Sea and Pacific Islands is expected join together to create an atmospheric river of moisture flowing toward New Zealand, bumping up against the high pressure system to the south of the country,” he says.
“The collision of several weather systems will generate potentially significant weather next week.
He says while there remains some uncertainty in the strength and track of the eventual weather system, at this stage the most likely areas to be at risk for flooding include Taranaki, Manawatu-Whanganui, the Wellington region, the top of the South Island and farther south along the West Coast.
“The eastern Coromandel, Bay of Plenty, Gisborne, and Hawke’s Bay should also be on guard for downpours, as east to northeast winds drive moisture onshore,” he says.
Noll says a secondary push of heavy downpours is possible on the North Island from late Wednesday into Thursday, with this latter round being one that Aucklanders will want to keep a close eye on.
“A period of strong, gusty winds may also come along with the rain,” he says.
“Beyond the active weather, it will also become very humid across the North Island, with some warm summer-like nights expected.”
Following the torrent Noll says some settled weather looks to return late next week or next weekend, possibly continuing into the week of the April 10.
“Thereafter, a strong signal for more heavy rainfall arrives in the lead up to the long Easter weekend,” he says.
“The upper North Island may stand the best chance of seeing more significant rainfall.”