South Westland was put on high alert following a MetService "red alert’' from January 18-20, when up to 800mm of rain was forecast in the Waiho River catchment at Franz Josef Glacier.
On January 26 MetService issued another warning of up to 250mm rain. Local authorities mobilised, but the alert scenarios did not approach those maximum volumes.
West Coast Regional Council chairman Peter Haddock said this week that the official forecasts "not matching" reality was a real problem for the region.
The last two forecast events, with the consequent warnings, had been totally wrong and succeeded only in scaring the public away, Mr Haddock said.
He called for the regional council and West Coast Civil Defence to use a range of forecasters, "as opposed to MetService."
Westland District Council declared a state of emergency on January 19 based on the red alert warning of up to 800mm falling in 47 hours. It cleared and shut State Highway 6 all the way from Ross to Haast.
The rest of the region north of Hokitika was also subject to an orange alert that weekend, but instead enjoyed balmy weather — after visitors and several events had already cancelled plans.
The January 26 rain warning also came to nothing, but not without sensational headlines, including on RNZ, which said the "already sodden" West Coast was to have another deluge.
Mr Haddock said offers of help poured in from South Island local authorities, and he responded by sending back photos showing the West Coast enjoying sunshine.
Chief executive Darryl Lew said the MetService forecasts for the last two events had overestimated the rain in South Westland.
"It is due to that, that a lot of regional councils don't just rely on MetService", Mr Lew said.
He was considering adding Niwa, as it had significantly increased its level of forecasting, noting that the Department of Conservation now used Niwa in a range of forecasts. That agency also had the benefit of providing corresponding flood modelling.
Mr Lew, who has a background as a hydrologist, said peak forecasting was "vital" to understand the potential for flooding.
Speaking after the meeting, Mr Haddock said he used a range of weather forecasters himself and discounted predictions by a large percentage of them, finding this was usually more accurate than official forecasts.
What had transpired was basically a non-event on January 18-19, and again the following weekend.
The Coast deserved better, given it is the same distance from Auckland to Wellington and businesses and visitors rely on reputable forecasts.
"It's the reputational damage with people thinking this is an unreliable place", Mr Haddock said.
MetService head of weather communication Lisa Murray said MetService took its role seriously and strove to give the most accurate and timely forecasts.
This included accessing all leading global weather models to collate a broad view, she said.
For the red and orange alerts in January, MetService had worked closely with the regional council.
However, all weather models had "strengths and limitations", one limitation being the "complex topography" of New Zealand.
"MetService high resolution models make improvements over this limitation. However, as is with the nature of forecasting, it is not a perfect science."
MetService had liaised closely with West Coast local authorities, including the regional council's hydrology team, before issuing the red alert.
- By Brendon McMahon
Local Democracy Reporter
LDR is local body journalism co-funded by RNZ and NZ On Air.
