Llanerch

Observations

Temperature forecasts

OpenWeatherMap forecast

Corbeaucast

PLEASE NOTE!

The UK Met Office moved its computing off-site during April & May 2025 which has resulted in less reliable availability of weather forecasts on their web API. Corbeau is therefore migrating from the Met Office to OpenWeatherMap. OpenWeatherMap offers instant, reliable weather forecasts at any time of the day and therefore offers a better local weather forecast upon which to base CorbeauCast microclimate forecasting.

If you have any questions about your subscription, do not hesitate to Contact us.

Forecasts vs observations

OpenWeatherMap forecast

Ecowitt weather station observation

CorbeauCast

Mildew advice

Powdery mildew and downy mildew are both important pathogens of grapevines and farmers typically spray sulphur and copper fungicides at 14 day intervals during the growing season. Conditions of high temperature and humidity encourage the growth and spread of mildews. CorbeauCast provides a daytime mildew risk indication of HIGH, MEDIUM and LOW. These correspond to vineyard conditions:

T>14 degC and RH >82%

T >14 degC and RH < 82%

T < 14 degC

At times of HIGH mildew risk, it is important to check the At Risk Hours number frequently because it can accelerate rapidly.

The At Risk Hours (ARH) chart provides a year-long record of accumulated mildew risk which can be considered when deciding on fungicide application. There are a number of potential intervention points:

75 hours – to tackle over-wintering spores

200 hours – to tackle mildew development

325 hours – to stop new mildew development

450 hours – to stop further mildew development and then every 125 hours if the season permits

Growing Degree Days advice

Growing Degree Days (GDD) is a useful record of how much energy a vine can potentially use to grow, flower, fruit and ripen. The GDD chart shows a cumulative total of GDD throughout the season.

It can be used to follow progress against expected phenological stages, alert to unexpectedly slow development and with a long-range weather forecast, to anticipate future stages.

Use the chart below to see how the vineyard or varietal parcels are progressing against expectations.