An increase in air pressure could potentially shield New Zealand from tropical cyclones that form to the west of New Zealand over the summer months.
It comes after NIWA along with MetService and other meteorological forecasting organisations in the south-west Pacific released a tropical cyclone outlook for the season.
The outlook from November to April 2024 shows the region should expect nine to 14 "named tropical cyclones", which is near or above normal for the region.
The outlook also showed four to eight severe tropical cyclones reaching category three or higher "might" occur anywhere in the region.
Normally, tropical cyclone activity tends to increase at the end of the season from February through to April, but this year the outlook shows it could be different.
"This season, there is a signal for enhanced activity during the first half of the season from November through January in the coral sea near Vanuatu and Fiji and near the Cook Islands," MetService forecaster Ben Noll said in a video describing the tropical cyclone outlook.
In some good news for New Zealand, the outlook showed there is a near normal to reduced risk for ex-tropical cyclones, which is a lower risk than this time last year.
As part of the video describing the tropical cyclone outlook, a graphic was used to show air pressure anomalies for November to January.
As part of the graphic, there was a "big red blob" to the northwest of New Zealand indicating above-average air pressure.
Noll said this could help shield New Zealand from potential tropical cyclones in the upcoming months.
"What stands out is this big red blob that we see near and north of New Zealand. This is higher than normal air pressure and it's pretty much the opposite pattern as to what we saw last year," Noll said.
"We saw during La Niña, lots of low pressure, lots of activity to the north of New Zealand. This year we are getting an opposite signal, it's potentially going to shield New Zealand to an extent. Features that are forming further up to the north have a tough time of breaking through this barrier of higher than normal air pressure."
Noll also pointed out an area of warmer sea temperatures to the northeast of New Zealand that could have a negative effect on the chances of tropical cyclone activity.
"Typically during El Niño it warms up in the central and eastern part of the region, it usually cools off further to the west but this year we have warmth right across the basin and this is a little bit atypical for El Niño," Noll said.
"It's going to have an influence on our tropical cyclone activity, just a little bit. There may be some opportunities for areas that are further to the west in the Pacific to get some cyclone activity."
It comes as NIWA reports a "disturbance" just south of the equator in the South Pacific, near Kiribati's Gilbert Islands.
MetService told Newshub there is still uncertainty around the "disturbance" but there is currently no risk for New Zealand.
"There's still a bit of uncertainty with regards to the exact sort of development of that tropical disturbance, so it is still quite far out and it hasn't yet formed into anything but we are keeping an eye on it just to see exactly how it develops. For the near future, there's no risk to New Zealand," MetService said.
MetService said the early indications are that the earliest chance it could develop up in the tropics is the middle of next week onwards.
