Renewed calls for rain radar

Nelson Mayor Nick Smith has renewed calls for a rain radar to be installed in the region after flash flooding hit the city on Monday – with more heavy rain expected on Wednesday afternoon.

Intense rainfall left parts of Nelson underwater on 26 May. Streets and several homes and businesses were flooded, drains were overwhelmed, and emergency crews scrambled to respond.

Nick says that a rain radar at the top of the South Island would help give the city more warning about serious storms.

“Our problem is the closest rain radar is in Wellington, it’s shadowed by the main range and as a consequence these events trap us quite nastily.

“This was an event that yes, we’ve had a warning that it was a relatively low level event, it turned out to be a lot more intense.

“We've been lobbying the Government both previous and current that that’s an investment that needs to be made by the MetService... improving their forecasting so we can better cope with the sort of event we had [on Monday]."

MetService said a new Nelson radar would cost $3 million and require a funding bid through the Crown’s budget process.

“MetService is contracted by the Ministry of Transport to provide meteorological and related services that deliver safety benefits to New Zealanders,” the agency says.

“Currently, we are not funded to provide a radar for the Nelson Tasman area, although we acknowledge it is one of several priority areas that we will continue to advocate for in future funding rounds.”

MetService says a radar was just one of the many tools used by meteorologists to monitor the weather.

“Radar is most useful for a very accurate live picture of what is immediately happening at a place at a given time, and therefore what is likely to happen over the next hour or two depending on the range of the radar and where the weather is heading.

“For effective response to severe weather events, much longer lead times are needed for warnings - preferably at least a day in advance. Radar pictures are in real-time so do not give this information.

“That said, any expansion of the observing network, such as new weather stations or radar facilities, assists our meteorological team build a more accurate picture of the current conditions across the country.”

MetService has 10 weather radars around the country, the most recent addition being the Otago radar in 2020.

“In recent years, our major radar projects have involved the Wellington and Canterbury radars being upgraded due to their 30-year-old technology.”

Tasman District Council principal hydrologist Martin Doyle says the council has been pushing for a rain radar in the region since 2010, after a major flood in the Aorere Valley in Golden Bay.

A marine radar at a cost of $30,000 has been installed, which gives a visual output of heavy rain but no numerical data, so it cannot be ingested into flood warning models.

- RNZ