Heavy rain expected, high winds possible

Posted by Nelson Tasman Civil Defence on 17 January 2017

Please be aware of the current MetService Severe Weather Warning for the ranges of northwest Nelson, during Wednesday night.

Heavy rain is expected and we also have a Weather Watch for the possibility of high winds across the region.

People camping and tramping in these areas should take care as rivers and streams will rise quickly with thunderstorms expected. Drivers in the region during Wednesday night and early Thursday should exercise caution.

A copy of the key information is below.

Please stay up to date with forecasts at the MetService website http://www.metservice.com

These sites are also useful:

  • River Flow Report
  • Rainfall Report
  • Tides                                                                             

AREA/S AFFECTED: THE RANGES OF NORTHWEST NELSON

A period of heavy rain is expected from Wednesday evening until Thursday morning. In the 12 hours from 6pm Wednesday until 6am Thursday, 100 to 150mm of rain is expected to accumulate. Peak intensities of 20 to 30mm per hour from Wednesday evening, with thunderstorms possible.

SEVERE WEATHER WARNING ISSUED BY MetService AT 10:40am 17-Jan-2017 via http://www.metservice.com

SIGNIFICANT HEAVY RAIN FOR THE SOUTH ISLAND WEST COAST AND CANTERBURY HEADWATERS, PLUS SEVERE NORTHWEST GALES FOR EASTERN PARTS OF CENTRAL NEW ZEALAND A deepening low over the Tasman Sea approaches the lower South Island on Wednesday, then continues to move eastwards on Thursday.

Meanwhile, an associated front moves onto the South Island during Wednesday, then moves northwards and crosses the remainder of the country on Thursday. This front is preceded by a very strong northwesterly flow, which brings heavy rain to western parts of central New Zealand and gales to much of the country.

The heaviest rain is expected about the ranges of Westland, where 400mm may accumulate from tonight until early Thursday morning.

Significant spillover into the Headwaters of the Canterbury lakes and rivers is also likely during this period. For Buller and the ranges of northwest Nelson, 100 to 200mm of rain is forecast in a 12 to 18 hour period from Wednesday afternoon into Thursday morning. This amount of rain will cause rivers and streams to rise rapidly, surface flooding and possibly slips.

In addition, damaging northwest gales are expected to affect much of central New Zealand for a time on Wednesday and Thursday. For Wairarapa, Wellington, Marlborough and Canterbury north of Ashburton, severe northwest gales gusting 150 or 160 km/h are expected in exposed places from late Wednesday afternoon. Winds of this strength can bring down trees and powerlines, damage unsecured structures, lift roofs and make travel hazardous.