Near average Tropical Cyclone season expected for Pacific

A ‘near-average’ Southwest Pacific Tropical Cyclone season is forecast this year, meaning any number from seven to 11 named cyclones occurring between November and April.

Three or four of these are expected to be severe, of Category Three or higher.

New Zealand however is typically only affected by one ex-tropical cyclone on average over this period and the coming season is expected to be ‘normal’.

Every year MetService, New Zealand’s official Tropical Cyclone Warning Centre (TCWC), works alongside NIWA, Australia’s Bureau of Meteorology and national meteorological services from other Pacific nations to produce a Tropical Cyclone Outlook for the coming season.

The average number of named tropical cyclones in the Southwest Pacific (including the Coral Sea) is about 10 per season.

TCWC Manager and severe weather expert Chris Noble says cyclone activity started particularly early this year with the development of Tropical Cyclone Liua in September.

“Despite the early start, we expect a near average number of cyclones to form in the coming season between November 2018 and April 2019,” he says.

MetService will begin to issue its daily Tropical Cyclone Potential Bulletin from 1 November, or earlier if considered necessary.

The bulletin is issued on the Metservice website at https://www.metservice.com/warnings/tropical-cyclone-activity

“This year, with the El Niño Southern Oscillation (ENSO) cycle tending to El Niño conditions, tropical cyclone activity is expected to be higher than normal to the east of the International Date Line, and lower further west,” says Chris.

“Although the tropical cyclone season typically runs from the start of November until the end of April, cyclone development doesn’t always follow the calendar and cyclones can form outside the season, such as TC Liua.”

“All communities throughout the South Pacific, including New Zealand, are encouraged to prepare for the coming cyclone season and remain vigilant for developing cyclones or other severe weather.

“It does not take a direct hit or a severe cyclone to cause significant damage or life-threatening weather. If severe weather is forecast, we urge the public to follow official advice from national meteorological services, disaster management offices or local civil defence.”

Around the globe, the role of monitoring and warning for tropical cyclones is performed by a WMO designated Regional Specialized Meteorological Centre (RSMC) or a Tropical Cyclone Warning Centre (TCWC), depending on the location of the cyclone.

TCWC Wellington, based at MetService, has warning responsibility for the area that extends from 160E to 120W between 25S and 40S.

Although it is very rare for a tropical cyclone to form in the TCWC Wellington area of responsibility, intense tropical cyclones do arrive from the neighbouring Brisbane or Nadi areas and they often retain their named cyclone status until near 30S.

Sometimes an ex-tropical cyclone will approach and may even cross New Zealand as was the case last season when former cyclones Fehi and Gita brought severe weather along with storm surge and coastal inundation to parts of the country.

If cyclones are expected to impact New Zealand with severe weather, official advice will be provided via Severe Weather Outlooks, Watches and Warnings issued by MetService. Even if land areas are not affected, warnings are still issued for vessels over the open sea.

For more information on Tropical Cyclones including Category ratings, visit https://about.metservice.com/our-company/national-weather-services/tropical-cyclones/

MetService issues Warnings, Watches and Outlooks for severe weather over New Zealand.

Warnings are about taking action:
* When severe weather is imminent or is occurring
* Issued only when required
* Recommendation: ACT

Watches are about being alert:
* When severe weather is possible, but not sufficiently imminent or certain for a Warning to be issued
* Issued only when required
* Recommendation: BE READY

Outlooks are about looking ahead:
* To provide advance information on possible future Watches and/or Warnings
* Issued routinely once or twice a day
* Recommendation: PLAN

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