Hawke’s Bay Regional Council figures reveal nearly 550 millimetres of rain fell in one area during Cyclone Gabrielle, but it says the real totals could be higher as strong winds may have impacted collection.
It comes after Hawke’s Bay Today reported a farm in Waiwhare recorded 730mm of rain during the cyclone, peaking at 250mm an hour into the gauge, more than double the peak forecast. The data was waiting to be verified.
HBRC marine, air and land science team leader Dr Kathleen Kozyniak said many sites across the region did not transmit data during Gabrielle after communication networks failed.
However, it was now receiving data, with multiple sites “recording significant rainfall totals”.
“The Glengarry site recorded 546mm of rainfall, the most of all the region’s sites, with almost 400mm falling in 12 hours at a maximum intensity of 56mm per hour.
“Sites along the southern coast had some of the highest falls in the region, as the high hills adjoining the coast are often exposed to storms arriving on easterly winds.”
Totals reached 450mm during the storm - about a quarter of annual rainfall there - with rainfall intensity peaking at nearly 40mm per hour.
The eastern area of Wairoa also received more than 500mm of rain. Meanwhile, 320mm fell in the Newstead site - in the western hills of the Ahuriri catchment near Puketapu - which was about one-third of the annual rainfall there.
Strong winds during Gabrielle meant some recorded rainfall amounts could be lower than actual totals, as the wind could have prevented rain from falling into rain gauges, Kozyniak said.
The two monitoring sites in the Pōrangahau catchment, which existed during Cyclone Bola, received “significantly more rainfall” during Gabrielle, Kozyniak said.
“Twice as much rain fell on those sites during the most intense 24-hour rainfall period of Gabrielle than during the most intense 24-hour period of Bola.
“Gabrielle’s rainfall was also more intense than Bola during six, 12 and 24-hour periods at the seven sites in the Tukituki catchment in place in 1988.”
HBRC chairwoman Hinewai Ormsby said the data reinforces the “staggering amounts of rain” received compared to what was forecast.
“It helps us understand how heavy the rain was in a relatively short period of time.
“While numbers such as these won’t provide comfort to those who have lost a loved one, a home or a business, they do put into context just what an extraordinary event Cyclone Gabrielle was.”