Storm tracking trial under way in Northland

The new system would help communities better prepare for extreme weather like the 2020 Northland flood. Photo / Peter de Graaf

A new storm tracking system is being trialled in Northland to improve monitoring of heavy rainfall events.

Northland Regional Council (NRC) Climate Change Working Party chairwoman Amy MacDonald said the system tracks storms down to a 500m resolution and displays exactly how much rain is falling.

The system, which is being trialled for a year from October 1, provides intelligence in remote parts of the region where local authorities don't have monitoring stations, or in alarm catchments – those which indicate more widespread flooding is likely – with no gear on the ground.

Crucially, it also provides "nowcasting", warning when significant weather is two to three hours off the coast.

Macdonald says nowcasting has been used on the east coast of Australia since the late 1990s and is also a critical technology for tracking the impact of climate change via increases in frequency of intense weather events.

"Nowcasting provides better short-term forecasts for heavy rainfall and helps communities plan and prepare for these events, minimising the effects of flash flooding."

The system can help fill gaps in traditional monitoring where hydrologically significant rainfall may either "fit between" rain gauges, or where that rain may be measured by the existing gauge network, but not in other areas.

Macdonald says the regional council scoped the system in 2018 after Auckland Council presented similar technology it was using.

Approximately 70 Northland-based local authority staff are now signed up to use the system, with the roughly $67,000 trial co-funded by the NRC and the Far North, Whangārei and Kaipara District Councils.

Auckland Council had found many more intense storms were impacting than the traditional monitored network detected.

"This was proven during the July 2020 storm in Northland. The new system detected two major storms, but only one using the traditional rain gauge network."

Aside from its more immediate benefit, longer term, the system allows local authorities to track the convective systems and their patterns and ensure engineering design is based on the best data.

It also enables them to expand network coverage to strategic locations without additional resourcing and to alarm catchments without deploying additional monitoring equipment.