Over the last few hours Tropical Cyclone Zena has formed across the northern islands of Vanuatu in the south-west Pacific . This is a late-season storm, with the southern hemisphere season typically tailing off in April.

As we said in last week’s blog, we had been expecting thunderstorm activity in this area to consolidate into a tropical cyclone. Over the past few days, the Met Office has been monitoring a slow-moving area of active thunderstorms which has brought torrential rainfall to much of Fiji and Vanuatu in the last few days. For example, 236mm of rain was reported in 12 hours on the volcanic island of Ono-i-Lau yesterday. Meanwhile, 208mm was reported in 24 hours in Nadi, on the western side of the main Fiji island of Viti Levu on Monday. Further heavy rain has affected the Nadi area today, with 29mm reported between 00 UTC and 12 UTC.

Tropical Cyclone Zena at 1330 UTC on 5 April 2016. Image from the Himawari satellite.

This system is expected to track east, or south-east towards Fiji over the next few days, bringing mean windspeeds of 45-60mph, with much higher gusts. However, Deputy Chief Operational Meteorologist Jason Kelly, who works in the Global Guidance Unit, said: “Of greater concern is the expected rainfall totals, with the Met Office’s Global Model signalling the possibility of a further 250-400 mm of rain across Vanuatu and Fiji by the end of the week. With much of Fiji still in recovery after the damage brought by Cyclone Winston in late February, further disruption to the islands is likely.”

Official warnings for the tropical cyclones in the South Pacific are produced by the Fiji Meteorological Service. The Met Office routinely supplies predictions of cyclone tracks from its global forecast model to regional meteorological centres worldwide, which are used along with guidance from other models in the production of forecasts and guidance. We also provide updates on current tropical storms via @metofficestorms on Twitter.