We will focus on winter weather events, for 1-3 month lead-times for cover crops, and 3-4 week lead times for the forestry case study (if time permits, on an ad-hoc basis).
The North Atlantic Oscillation (NAO) is an important mode of climate variability in North European climate, and drives much of the signal in winter climate. Recent advances in seasonal forecasting have increased predictability in the winter NAO have led to significant improvements in seasonal climate predictions for Northern Europe during the winter, with advance warnings of cool/dry vs. wet/mild conditions possible several months ahead.
The decision to plant a winter cover crop (and which crop to plant) depends mainly on forecast precipitation (and to some extent temperature) for the coming season, as well as soil moisture conditions.
Since seasonal forecasts are not currently targetted at the UK land management community, most current land management decisions rely on short term forecasts (mainly 1-5 days). For instance, knowledge of a forecast wind, or rainfall event could influence a decisión on when to spray crops with pesticides, or when to apply fertilisers. In this context, information on even shorter timescales (e.g. hourly forecasts and radar images) can be particularly useful. Longer-term decisions such as which crop to plant are generally not informed by weather forecasts, since they would require information on longer timescales. This prototype project aims to complement shorter-term weather information with three month outlooks during the Winter, to provide additional contextual information to support decisión making. For example, knowledge of warmer and wetter conditions over the next three months, combined with a short-range forecast of a dry spell might lead to a decisión to peform agricultural operations (e.g. plouging) more imminently than otherwise.
For winter 2014/2015, we initially provided a small subset of farmers with paper and .pdf format forecast sheets which describe the likelihood of experiencing below, normal and above normal temperature and precipitation for the next three months, on a rolling monthly basis. We hope this information helped support better land management decisions as described above. During Winter 2015/2016, we are providing 14 day site specific forecasts for temperature and precipitation across South West UK, alongside UK-scale three month outlooks, via our interactive website (login required).
The potential to provide short-lead time warnings of cold weather for forestry is based on a weather phenomenon known as a Sudden Stratospheric Warning (SSW). An SSW means rapid warming between 10 km and 50 km in the atmosphere, which more often than not leads to cold snaps over the UK. Currently individual SSWs can be predicted about a week in advance, and they can be detected early on with satellite and other observations. For the forestry case study, winter planting on cold ground and accessibility (due to frost heave etc) are key issues, so advance warning of several cold snaps in a row is important. The 2013/2014 winter seasons may provide useful case studies for winter.
The links below are videos explaining long range forecasting and SSW:
Long range forecasting: