By Jamie Morton of 
File pic Photo: Supplied / Steve Gibbs
The southwest Pacific's first tropical cyclone of 2024 could form within days - but meteorologists say there is no sign yet of any risk to New Zealand.
Forecasters are closely tracking potential for a tropical low over the Coral Sea to form into a cyclone system, with Australia's Bureau of Meteorology currently giving a "high" chance (or 55 percent) of it reaching cyclone strength by early next week.
MetService's latest outlook picked a moderate risk (20 to 50 percent) of a system developing in the area, between Queensland's northeast coast and New Caledonia, from Saturday.
A tropical low in the Coral Sea is now rated as a high (55%) chance of being a tropical cyclone from Sunday. The system is expected to remain offshore over the next 7 days, however uncertainty in its movement increases from early next week.
— Bureau of Meteorology, Queensland (@BOM_Qld) January 16, 2024
TC Outlook: https://t.co/hw63OUtpAP pic.twitter.com/nij1q6dvPh
"We've been very lucky through the Christmas period, with it being a relatively settled time in terms of tropical cyclones, but sadly, things are about to get a bit more active up through the Coral Sea," MetService forecaster John Law said.
"It is an area of concern, and for us here in New Zealand, it's looking like the second half of the month is going to be a different story to that first half."
Whether a system ultimately pushed south into our neighbourhood as an ex-tropical cyclone remained to be seen, "but it's definitely a situation to be aware of, especially island groupings around that way".
National Institute of Water and Atmospheric Research (NIWA) meteorologist Ben Noll said that, among other favourable conditions for cyclone development over coming weeks, surface temperatures in the Coral Sea were running warmer than average.
"Basically, west of New Caledonia, extending all the way to the coast of Queensland, we're seeing moderate to strong marine heatwave conditions.
"At this point, the heatwave also extends southward into the northern Tasman Sea, and also encompasses the North Island's coastal waters, along with the top of the South Island - so it's pretty widespread."
Over the last month, a marine heatwave formed & intensified in the Coral Sea, Tasman Sea & more recently near New Zealand
— NIWA Weather (@NiwaWeather) January 16, 2024
Near New Zealand, seas are 1-3˚C warmer than average, with the most unusually warm water near Waikato, Auckland, Coromandel, Bay of Plenty & Hawke's Bay. pic.twitter.com/dSekmv7D8e
This ocean warmth was contributing to summer temperatures in New Zealand - including uncomfortably hot nights - despite earlier expectations that it wouldn't be such a big factor here amid this season's El Niño.
Up in the Coral Sea, meanwhile, the marine heatwave could increase the potential for a formed cyclone system to intensify, while contributing more moisture.
"I'd agree it's too early to say what we can expect with this one," Noll said of its implications for New Zealand.
"But we do look to be going into what I'd describe as an unsettled pattern in the Tasman Sea, around the same time this tropical cyclone may form, and what that can do is potentially draw moisture at some point from the system."
Coral Sea tropical low 05U is now on the Joint Typhoon Warning Center radar with the invest name of #90P. With low wind shear & sea surface temps of 30° to 31°c, its likely to become a goliath next week. Still longer term uncertainty but NZ needs to keep an ️on this one pic.twitter.com/JMAi6mflw1
— Hauraki Gulf Weather (@HaurakiGulfWx) January 16, 2024
Warmer seas happened to help fuel last month's disastrous Jasper - which reached Category 4 strength and may have been Australia's wettest tropical cyclone on record - and also last February's Gabrielle.
While the New Zealand region has received remnants of faded tropical cyclones so far this season, it's yet to receive an unwelcome visit from an ex-tropical system, as occurred multiple times last season.
NIWA has already forecast an elevated risk across large areas of the West Pacific, but picked a lower threat for New Zealand, with a subtropical ridge of high pressure above the country likely to prevent big rainmakers from travelling here with the relentless frequency of last summer.
Noll added a globe-circling pulse of rain and thunderstorms called the Madden-Julian Oscillation (MJO) could again prove a cyclone-building factor as it passed through the region next month.
"That's happening in pretty much the same region, which means this tropical cyclone may prove the first in a string of potential ones over the next four to six weeks."
- This story was first published by the New Zealand Herald.
