3.1.5.b What is the upcoming weather forecast?

Overview

Weather forecasts should be studied carefully during the harvests. There are many sites dedicated to monitoring and forecasting the weather during this crucial period. Information is generally provided by the region or the department. To obtain a more local, more reliable forecast, weather stations can be set up in different places in the vineyard. At Chateau Latour, for example, real and virtual weather stations have been placed inside and outside the enclos , with the objective of having a station for each section of the vineyard so as to best represent their respective microclimates.

Will upcoming weather conditions improve the grapes' state of ripeness?

Weather forecasts are essential when determining the harvest order. If upcoming weather conditions are unfavourable due to low temperatures, for example, there is little advantage in pushing ripening further. Colder temperatures associated or not with rain prevent or allow very evolution in the ripening process. On the other hand, when conditions are favourable, it is possible to postpone harvesting. This will not only depend on the health of the vines but also on the aromatic profile that the winemaker is seeking to give the wine.

Consequences of rain or drought on the harvest

Rainfall can cause a significant increase in berry volume and create a dilution phenomenon. This can be quite problematic as dilution prior to harvest can result in a flat mouthfeel when tasting the berries. In addition, as ripening progresses, there is a loss of elasticity. Heavy rain can cause the berries to burst due to a sudden increase in volume, with the direct consequence of an increased risk of contamination by Botrytis.

Grape varieties can be characterized by their skin permeability index SPI and by their thickness Penetrometry. When the skins become very thin and easily tearable, the risk of berries bursting due to rain and Botrytis contamination can be high. Some grape varieties being more sensitive than others, it can be judicious to harvest them before heavy rain.

High temperatures and heat waves within a few days of the harvest can also have adverse effects on the harvest. A severe drought is likely to accentuate water stress already present in the plot at this time of year. This can lead to withering of the berries and concentration. In extreme cases, severe stress can cause ripening to stop: in order to maintain its winter reserves, the vine halts the ripening process. This results in a loss of ripening potential and therefore of the quality potential of the grapes and possibly of the wines produced from these berries. Intense light combined with high temperatures can also cause scorching of the grapes, giving them a more cooked character, with flavours of cooked/candied fruit.

Contribute Print

Contribute