Rain has fallen, but more is needed for those in the driest parts of New Zealand. Some regions still have a “late summer/early autumn” look to them despite the rain that has fallen so far this month.
El Niño has officially gone now – but autumn’s usual westerly driven weather means many may not notice an immediate change, and we’re still seeing eastern parts and northern parts of both main islands leaning drier.
Soil moisture deficit maps show the eastern half of Northland, the eastern side of Auckland, the Hauraki Plains, Coromandel Peninsula, much of Bay of Plenty, Gisborne, East Cape, Hawke’s Bay, eastern Manawatū, southern coastal Taranaki to Whanganui, Wairarapa, southern inland parts of Marlborough, and a decent chunk of Canterbury are all “thirsty”.
Some of these places are much drier than normal right now and need at least 100mm of rain (preferably not in one day!) to change things.
Meanwhile, on the wetter side of the scale, the western side of Northland, western Waikato, King Country, the northern half of Taranaki, northern coastal Marlborough, Golden Bay/Tākaka, Southland and Central Otago all lean wetter than usual right now. In particular, Southland and King Country have both had heavy rain and showers in recent weeks.
This set-up means that, ideally, we need a rain event that comes in from the north or northeast. This would “fix” many of these dry areas.
Unfortunately the wet easterly flow is north of New Zealand, lining up with Brisbane and southern Queensland over the coming week. They have 100mm to 200mm possible, whereas in NZ some eastern areas have almost none in the next week due to more high pressure and westerly driven wet weather. However, the month of April does have some chances of ending wetter for NZ. As El Niño’s weather pattern continues to fade it will allow for much larger breaks in high pressure zones west of NZ.
With the rain hitting Brisbane this week, all it takes for that wet easterly to come into NZ is the high over the Tasman to be replaced by a southerly and the two flows can merge to spin a low.
Some long range modelling shows this – but I’m always nervous about locking in rain for those in need when it’s on the hunch of one long range computer model.
But still, the fact some models are picking it shows there is enough uncertainty in the atmosphere – a sign that the stubborn dry highs of El Niño may finally be breaking up to some degree in our part of the world.
The air is still fairly mild – there’s been a distinct lack of frosts so far, though a few over the past few days have popped up.
Upcoming Highlights:
• High pressure kicks off this week
• High pressure exits the country mid to late week, allowing for warm sub-tropical winds for many
• Possible large low for NZ in the final days of April (not locked in)
