Tropical low expected to become cyclone tomorrow as Auckland, Hawke’s Bay among regions under severe thunderstorm watch

Forecasters are on high alert with much of the North Island under weather warnings and watches and a tropical low in the Pacific now expected to become a cyclone on Tuesday.

A weather front across the northern parts of the North Island will bring extensive rainfall for Coromandel Penisula, the eastern parts of Bay of Plenty and Gisborne.

MetService has issued Coromandel Penisula with a heavy rain watch from Monday 7am to Monday 7pm. 

The eastern parts of Bay of Plenty are under a heavy rain watch too from Monday 7am to Monday 4pm.

And the already drenched Gisborne is in for some more rain. The region is under an orange heavy rain warning from Monday 7am to Tuesday 4am. 

In addition, a severe thunderstorm watch has been issued across 12 regions for eight hours from Monday 1pm to Monday 9pm. 

The severe thunderstorm watch has been issued from Northland, Auckland, Waikato, Waitomo, Taumarunui, Bay of Plenty, Rotorua, Taupō, Hawke’s Bay, Taihape, Wanganui and Manawatu. 

MetService meteorologist Karl Loots told Newshub the severe thunderstorms could bring “torrential downpours”.

“These storms are likely to bring localised heavy rainfall and possibly hail as well. In addition to this, there’s a possibility that these can be quite slow-moving. So we can see localised downpours with these anywhere from 25 to 40 millimetres per hour.”

Cyclone watch 

A low-pressure system in the tropics is in its early stages but Loots says it’s intensifying. 

The low has not yet been deemed a tropical cyclone by Fiji Meteorological Service but Loots expects it to be named in the next 24 to 48 hours. 

In a tweet, NIWA said the Fiji Met expects a tropical cyclone to form by tomorrow.

MetService said in an 11am update on Monday the low is “in a favourable environment” and is highly likely to develop into a tropical cyclone within six hours.

The tropical low is expected to become a cyclone while to the northeast of Vanuatu and then expected to recurve south and remain close to Vanuatu throughout Wednesday.

“Large waves, heavy rain, and gale to storm force winds are expected to impact Vanuatu from Tuesday,” MetService’s bulletin said. 

The tropical cyclone is then expected to reach severe tropical cyclone category three or above. 

“It then turns southeast during Thursday and is expected to move out of the tropics later Friday.”

Loots doesn’t expect much impact from the low, but reiterated that the system has not yet formed fully and it’s “extremely early days” 

“These tropical systems can be very difficult to track, very far out, particularly before they have formed properly.”

The low is expected to be within Aotearoa’s area of responsibility by Thursday night. 

In a tweet, NIWA shared the latest modelling from European Centre for Medium-Range Weather Forecasts (ECMWF) has many scenarios seeing the system move north and east of Aotearoa.

“Let’s hope it stays that way.”

MetService says another tropical low over the Coral Sea is likely to move east, with a chance of it developing into a tropical cyclone becoming low on Wednesday, moderate on Thursday and high on Friday. 

“This system is expected to follow a similar track to tropical low 08F [the low mentioned above], and move across or close to Vanuatu later in the week.