Thursday, 11 February 2016 10:44

Early season conditions very variable

Written by  Tessa Nicholson
Waipara, Marlborough and Central Otago ended the first half of the season in very dry conditions. That will impact on the vines in the coming months. Waipara, Marlborough and Central Otago ended the first half of the season in very dry conditions. That will impact on the vines in the coming months.

The monitoring of 28 vineyard sites in five wine-growing regions of New Zealand, has provided the first ever start of the season weather picture for the industry.

Rob Agnew from Plant & Food Research in Marlborough is one of two people collating the weather information from Gisborne, Hawke's Bay, Marlborough, Waipara and Central Otago that feeds into VineFacts, a subscription newsletter.

While the newsletter has been in existence for 20 years, it is only this season that it has been extended outside of Marlborough, thanks to funding from NZW, Sustainable Farming Fund and Marlborough Research Centre.

When Agnew collated the figures from the first four months of the season (September through December), they showed how the season began as much cooler than the long-term average, with North Island regions affected by rain, far more so than the South. Below is a summary of the first four months of the 2015/16 vintage, region by region.

Gisborne

September in Gisborne is described as being cool and very wet, by Agnew.

"The total amount of rain was 183.2 mm where as the long-term average (LTA) is just 69 mm. So the region had almost two and a half times more rain in September than they would normally get."

The mean temperature was also lower – at 10.9°C, down from the LTA of 12.1°C.

October saw the temperatures begin to rise, and the rain ease off. In fact there was only 58 mm of rainfall in Gisborne during October, below the LTA, and the mean temperature was 14.7°C, 0.7°C above average.

Agnew describes November as being average in terms of temperatures and growing degree days (GDD), although it was once again a wet month, with 94 mm of rainfall.

December was again cool and wet, with mean temperatures 1.5°C below the LTA and GDD more than 40 behind the average.

Agnew says the first half of the growing season in Gisborne, can be summed up as being cool and wet.

Hawke's Bay

September: Again the season began very cool, with the mean temperature 1.5°C below the LTA. It was also very wet – just like Gisborne, with 198.7 mm of rain, nearly four times the LTA. GDD were 36 percent of the average, although as Agnew says, that is not as significant in a month like September, as it would be later in the season.

October: While the maximum temperature was up 1.2 deg, the minimum was down a degree, resulting in average mean temperatures for the month. Rainfall dropped considerably, 35% of the LTA, making it a dry month. GDD were dead on the LTA.

November: A cool and wet month. Temperatures were down, as were GDD and rainfall was up.

December: There was no real let up in Hawke's Bay once December hit. Temperatures remained below average, as did GDD. However the rainfall that has dominated a number of the previous months was half of the LTA.

In summary – Hawke's Bay can be described as cool and wet.

Blenheim

2015 goes down as the driest year on record for Blenheim, so it is no surprise to see that each of the first four months of this growing season are characterised as being dry.

September: This was one of the only months of the year that Blenheim had an average monthly rainfall, with a total of 54.4 mm. Hopefully they made the most of it, because there wasn't much more to come before the end of the year. Like all other regions, September was cool with an average mean temperature of 9.7°C, well below the 11.2°C LTA.

October: Things started to warm up this month, with Agnew describing the period as warm and very dry. With a total of only 6 mm of rainfall, you can understand why. All other facets were up though, maximum and minimum daily temperature, mean temperature and GDD.

November: Another warm and very dry month – 2.8 mm of rainfall, with higher than average temperatures and GDD.

December: Cooler temperatures this month saw the mean temperature drop back, along with GDD. Given this is the major month for Sauvignon Blanc flowering, the lower than average temperatures may impact on yields. Some Sauvignon Blanc that flowered early in December during a brief period of warm temperatures is likely to have above average yields, whereas blocks that flowered later during cooler temperatures are likely to produce lower yields

In summary – Blenheim is described as having average temperatures and very dry conditions between September and December.

Waipara

Another region in the midst of a severe drought, Waipara received very little in the way of moisture during the start of the season.

September: Cool and dry.

October: Just like further north in Blenheim, Waipara gained some traction this month, with warmer than average conditions.

The average mean was 1.3 higher than the LTA, GDD were well up and rainfall was 11.2 mm, 21 percent of the LTA.

November: Another warm and very dry month for the region. Rainfall was 21.2 mm, but only 41 percent of the LTA.

December: After two months of having higher than average temperatures, December was a cool month to end the year on. All temperature parameters were down, as were GDD, and only 55 percent of the LTA rainfall for the month fell.

Agnew summarises Waipara as having had an average four months (temperatures and GDD) and it was also very dry.

Central Otago

Probably the warmest and most stable of all the five grape growing regions monitored, Central only suffered one month where Agnew says temperatures and GDD were lower than average.

September: Just like every other region, Central's September was cool while also very dry.

October: The start of things to come in terms of average maximums and mean temperatures. They were well up, as were GDD. This was a warm and dry month.

November: The frosts that hit the region during this month meant the average minimum temperature was lower than average – but everything else was above average, with the exception of rainfall.

December: Once again the average minimum temperature for the month was lower than the LTA. But average maximum was up by 2.2°C. GDD were also up, rainfall was down. A month Agnew describes as warm and very dry.

In summary – Central Otago experienced a four-month period of warm temperatures and very dry conditions.

If you would like to find out more about VineFacts, visit http://www.nzwine.com/members/vinefacts 

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