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Better tropical storm forecasting

1st May 2019

Next week, academics from ARUA and a number of British universities will meet to discuss closer research ties. Here, the University of Leeds describes one of the international collaborations it is involved with.

Every year about 5,000 people die on Lake Victoria in Africa, many in storms and other severe weather events, according to official figures.

The lake and densely-populated area surrounding it, straddling Uganda, Tanzania and Kenya, is prone to sudden and extreme storms. But they are difficult to predict.

Similar storms can cause devastation and loss of life right across tropical Africa.

An international collaboration of weather scientists and meteorologists led by the National Centre for Atmospheric Science at the University of Leeds is looking at ways to improve forecasting of these high-impact events.

The collaboration, known as African SWIFT — Science for Weather Information and Forecasting Techniques, involves 10 African universities and forecasting agencies along with two British universities, the Met Office and the Centre for Ecology and Hydrology in the UK.

Doug Parker, Professor of Meteorology in the School of Earth and the Environment at Leeds, said: “These tropical storms can be devastating and as researchers we need to develop a better understanding of the science that explains them.

“We also need to ensure front line forecasters can apply the latest modelling and weather science in their work.

“The aim is have forecasts that are more accurate, have public confidence, and allow people to make decisions that minimise risk to themselves and their families.”

For two weeks, the international collaboration has met at the Kenyan Meteorological Department in Nairobi to test and revise existing weather models. Known as a ‘testbed’, it is an established technique in weather science to rapidly pass on the latest research to operational forecasters.

Tropical storms in the Lake Victoria region result from moist air over the lake interacting with the strong temperature differences between the lake and the adjacent mountains.

As the air warms, it rises and expands and the moisture turns to rain. This ‘convective precipitation’ can be very sudden and very intense.

The World Bank has estimated that there are some 5,000 deaths each year on and around Lake Victoria, many attributed to extreme weather, with torrential rain and high winds capsizing boats.

Many of the existing models for predicting convective rain storms fail to forecast the most extreme events.

The Met Office in the UK has been working on an alternative weather model to try and capture the dynamics of the convective systems over Lake Victoria.

The model is high-resolution enabling forecasters to predict not only how a storm will hit but where, and identify localities that could be badly impacted.

It is run many times every day, to give forecasters a range of possible future predictions.

Dr Andy Hartley, regional model evaluation scientist at the Met Office, said: “Understanding this model is beneficial to African forecasters because it allows them to give communities more accurate and timely warnings of strong winds, or localised flooding.

“Closer to the event, we would expect the models to provide a more accurate forecast of the location and the intensity of the event.”

The forecasters were also being trained in “nowcasting” to give very accurate predictions about what is going to happen over the next one, two or three hours.

The testbed also looked at forecasting weather patterns more precisely in Senegal, Ghana, Nigeria and Kenya.

The project to improve weather forecasting in Africa is funded through the UK Global Challenges Research Fund (GCRF), part of the Government’s aid budget with the aim of using the best scientists to try and find solutions to the world’s biggest problems.

The GCRF grant was made by the UK Natural Environment Research Council(NERC).

Ned Garnett, Associate Director of Research at NERC, said: “I think that this is an excellent example where improving our fundamental understanding of weather patterns, and incorporating this understanding in to operational models, can provide the predictions needed to help people and businesses worldwide to make confident, informed decisions.

“This is even more important in places like Lake Victoria where accurate forecasting can mean the difference between life and death.

“By bringing international expertise together via GCRF, this activity will ensure that the latest models are deployed in areas where they are needed most.”