Cyclone Vaianu Threatens NZ Growers with Wind and Rain

The system comes early for Bay of Plenty with the storm winds building Sunday morning, followed by an intense period of wind gusts from Sunday afternoon coupled with heavy rain.

Bay of Plenty copes with rain better than Hawke’s Bay due to its geography and volcanic soils. But forecast high winds and gusts for the Hicks Bay area present the risk of damage to kiwifruit vines from Opotiki through to Te Kaha.

Rain this late in the season has impacts on late season Avocadoes and kiwifruit as it impacts fruit DM. At this stage wind is a bigger risk that growers have more control over, being able to prepare for by checking and securing netting/covers and windbreaks.

Waikato

Blueberries are in full swing with picking in the region. Berries do not like long periods of wet weather. The region’s fast draining soils mitigate some of the rainfall risk. High winds are a risk to net structures and berry growers are likely to have some windfall losses.

Temperatures through Waikato remain warm (circa 20 degrees) which brings a rot risk and can promote bug growth.

The upside of the speed of this system is that by Monday it’ll clear and Tuesday looks to be settled.

Gisborne

While the region is not set to bear the brunt of the storm, it is forecast to see damaging wind gusts over 100kph and between 20mm rain in Gisborne and 100mm of rain in the ranges. 

Hawke's Bay

The system is spinning clockwise bringing in rain to the Hawke’s Bay from the East. This will see it dump significant amounts of water into the Waipawa and Waipukurau catchments. Over 130mm is forecast in the Ruahine Ranges which could place pressure on stop-banks.

Rainfall on the Heretaunga Plains is not as heavy with 40mm forecast between Saturday and Monday.

Wind is a larger risk factor for growers and it will rapidly change direction. Wind peaks on Sunday afternoon from the East with gusts up to 80-100kpm. Then, following a brief calm period of approximately an hour, conditions will see a fast swing in direction to a massive westerly as the eye of the storm moves through.

180-degree swings of these magnitudes can be damaging to apple trees as late pick trees will still be under heavy fruit loads and will potentially be waterlogged.

Tukituki catchment growers are at particular risk. Soils should be able to handle 100mm in a 6-hour period, but it will be intense.

It is noted that the last significant rainfall was 21st January where some 80 to 100mm fell across the region. 30mm fell in mid-February. March and early April has been particularly dry with some 20mm-40mm total recorded since the 16th of February and soils are dry.

Wairarapa, Manawatu and Wellington

Grape growers in these regions are forecast to experience significant levels of rain coming from the South-East and high winds as the system funnels moisture up through Cook’s Straight. 

Marlborough

Blenheim is likely to catch the edge of the system at this stage with winds wrapping in from the South-East before the system moves out west of the country.

Nelson

Forecasts indicate the potential for Nelson to largely miss out, with only 10-20 mm of rain at this stage as the system moves further East.

Simple Take Outs For Growers and Staff:

• Most grapes are picked for the North Island. Top of the South growers can expect to see intense rain.
• Apples: Pick as fast as you can now to get as much fruit off to lower weight loading on the trees.
• Little can be done for kiwifruit as picking is packhouse dependent. There will be wind damage to vines. Check your orchard covers/wind breaks/netting and secure.
• Clear any drains/ditches/packhouse and office spouting.