Rain gauge a telling tale of Napier storm

This week's deluge in Napier peaked with more than 230mm of rain in the CBD. Photo / File

The storm that devastated Napier on Monday night has been compared to a similar deluge that ripped through countryside and coastal areas east of Napier and Hastings in April 2011.

But it was both a radical contrast and a very different storm track.

While this week's deluge peaked with more than 230mm of rain in the Napier CBD, some of the rainfall was less than half the extremes recorded in the big event nine years ago.

The comparisons come in recordings kept by the Hawke's Bay Regional Council, which operates a network of 38 telemetered stations from the Urewera country to Central Hawke's Bay, including a CBD gauge atop its building in Dalton St, Napier.

That gauge recorded 231.5mm, consistent with the Napier City Council station recording of 237mm less than a kilometre away at Nelson Park.

The southernmost extreme of the deluge was 201.5mm at the council's Waipoapoa recording station (south of Hastings and Havelock North). But it had 431mm in 24 hours at the height of the late-April 2011 storm which devastated an area from Te Awanga to Waimarama, said regional council principal scientist – air Kathleen Kozyniak.

Amid that storm, homes were evacuated in Napier, and at Waimarama the main access bridge was damaged and impassable.

The localised nature of the severity of Monday's rain was highlighted by other rainfall figures for Hawke's Bay. Only 142mm was recorded at Hawke's Bay Airport on the northern fringes of the city, 95mm at Glengarry, and 144mm at Mote, west of Napier.

In Hastings, 94.5mm had been recorded over Monday-Wednesday, and on Monday there was just 44.5mm of rain.

At Ngahere, a site of some of the heaviest rainfall in the Kaweka Range and a significant contributor to the river levels of Hawke's Bay, more than 160mm of rain fell in the past three days, but it was barely a third of the 476mm recorded over a similar period late in September 2015.

By 10am Wednesday, about 255mm of rain had been recorded in the Napier CBD since Monday morning – about 10 inches under imperial measurements used more historically in New Zealand.

Meanwhile Napier's turned a distinct weather corner and is heading for a fine and sunny weekend with highs of between 21C and 23C forecast from Friday through to Sunday.