El Niño has officially arrived. A majority of NIWA’s criteria for classifying an El Niño event were satisfied during September. In particular, the Southern Oscillation Index was firmly in El Niño territory, suggesting the atmosphere has become coupled to the ocean.
There’s around a 100% chance of El Niño continuing during October-December and over a 95% chance that it will persist through summer.
I won't go into detail about El Nino and La Nina and the Southern Oscillation Index (SOI). You can google the detail or visit NIWA niwa.co.nz/climate/information-and-resources/elnino
We are always very interested in this weather pattern because it has significant influence on weather in the vineyard. An El Nino weather pattern is generally good for us and La Nina weather pattern generally not so good.
The Southern Oscillation Index alone is not the full picture. El Nino and La Nina may be strong, weak or neutral and may not start or stop in any particular part of the season.
What El Nino and La Nina mean for us at Grasshopper Rock is unique to our location and local geography among the mountains.
El Nino means more winds from the SW versus La Nina which has more winds from the NE.
Grasshopper Rock in the Alexandra basin is in the SE corner of the Central Otago winegrowing region meaning it is further from the west than other the sub-regions.
The vineyard location receives less rain in El Nino because it is further from the west and beyond the reach of the rain laden westerly winds which tend to dump most of their moisture in the west.
This is good for us because a dry warm flowering in December is the ideal scenario to achieve a good even fruit set.
During the last three years however the weather pattern has been La Nina which has meant more easterly weather which tends to bring us more moisture. If it rains during flowering as has been the situation in the last three years, it makes a successful flowering and fruit set more challenging and can increase disease pressure (powdery mildew) through the season.
El Nino years have been some of the best years for making wine because they tend to bring drier conditions.
Unfortunately long term weather forecasting doesn't tell us exactly when weather will occur. If we could guarantee fine settled weather during December for flowering we would be happy vignerons.