The weather is notoriously hard to predict. Ever since Michael
Fish famously declared on national television in October 1987
that there was going to be no hurricane, the day before the
worst storms since 1703, people have been wary of weather
reports. But in fact our ability to forecast the weather has
improved immeasurably in the past few decades: mathematical
researchers have been working with meteorologists,
oceanographers and physicists since the end of World War II on
the problem. There are many difficulties in weather prediction.
When it's raining in your town, it is quite possible for it to
be dry (or even sunny!) just a few miles away. No TV presenter
can show that level of detail on a weather map, and whatever the
presenter says somebody will complain that it wasn't right.
Another difficulty is that the weather is chaotic - which means
that tiny changes in the atmosphere today can result in
completely different weather patterns in a few days' time. This
is known as the "Butterfly Effect": if a butter