Weather forecasts provide information about the meteorological conditions expected over the next few days, weeks or months. Seasonal forecasts make it possible do the same over several months by proving information about long-term averages. Forecast averages are based on conditions at the Earth’s surface, in particular, slow fluctuations in the sea-surface temperature of the global oceans which can influence weather patterns. These long-term influences are not easily noticed in day-to-day weather events but, crucially, they do become evident in long-term weather averages.
The best known are those associated with the El Niño phenomenon, which is a warming of sea surface temperature in the tropical Pacific that occurs on average every three or four years, disrupting the normal pattern of weather around the globe. Large changes in seasonal rainfall that lead to droughts in some regions and floods in others can be forecast ahead of time by taking a more long-ranging look at our weather patterns.
Sea surface temperatures can be predicted, to some extent, up to about six months ahead. The links between them and weather can be represented in computer models of the atmosphere and ocean. Complex modelling systems, developed by the UK Met Office, are used for making daily and long-term change prediction forecasts. The organization currently provides worldwide seasonal forecasting through GloSea5, an ensemble prediction system using high-resolution atmosphere-ocean coupled climate modelling. Data readings are taken from multiple sources such as ocean, land and atmosphere conditions to create future predictions and currently is accessible worldwide.
Over the past years, the use of advanced seasonal forecasting to fight the effects of climate change on farming has shown promising results. The work of the UK Met office on a project in Ethiopia proved that dynamically downscaling seasonal forecasts can generate additional smaller-scale information such as rainy season onset and dry spell lengths. A new project focusing on drought and flood mitigation in Uganda will build on these exciting findings to bring improved seasonal forecasting to Uganda to a 25km radius.
The Drought and Flood Mitigation Service (DFMS) aims to improve African agri-business’ decision making with better information about climatic changes or conditions for harvesting, for instance. The project is a collaborative effort between professional UK companies underpinned by the UK Space Agency.
Feedback gathered by the DFMS team from agri-business in Uganda showed that greater improvements on the current GloSea5 system could be made as the need for seasonal forecasting increases. In collaboration with the Met Office, the platform will include stand-alone services, such as the seasonal weather forecasting which is vital to many agri-business, as well as complementary components such as Earth Observations and pictorial evaluation tools. The latter gives a great level of insight into land cover, livestock and crops as well as further validating the seasonal forecasts, therefore, making them more reliable. The platform is currently under development and will launch in March 2019.