Mrs Bale (the housekeeper of Rocky and Madge in As Time Goes By) frequently provides the forecast of the English Channel. I have noticed that this is often used as a technique of foreshadowing the events in the show. But, aside from a plot device, why is Mrs Bale so fascinated by the weather report for the English Channel?
BBC Radio 4 has provided the Shipping Forecast on long wave since time immemorial. This is broadcast for use by all shipping around the British Isles.
There are many people on land in Britain who listen to the shipping forecast even though they never go near the sea. The forecast always takes the same form, a gentle litany of sea areas, wind strength, wave height etc… This is seen by many as soothing.
It has become a stereotype that people of a certain age, who listen to Radio 4, will listen to the shipping forecast. It is perceived by many as more accurate than the more glossy television weather forecasts. Mrs. Bale fits into that stereotype and that is the joke.