What does a red sky in the morning mean? Londoners wake up to gorgeous sunrise

Is the saying 'Red sky in the morning, shepherd's warning' true?
Sunrise
The eye-catching red skies will sadly fade as Thursday progresses
Jeremy Selwyn

Londoners woke up to a red sky on Thursday (December 14) morning. But, while the colour provided a ray of light in dreary December, it carries a traditional warning.

The BBC forecast another grey day with highs of 8C before a weekend of more frequent sunshine. This comes as the UK approaches its shortest day of the year next week

However, there has not yet been any snow during Advent for Londoners to enjoy alongside Christmas light switch-ons.

The eye-catching red skies will sadly fade as Thursday progresses. However, the city’s residents have shared their best pictures and thoughts on X, formerly Twitter.

Alastair Hilton wrote: “Got on my bike to cycle to Tower Bridge to watch the sun rise, but first, there was this; sunrise over the gasholders at Broadway Market. A really rather pleasant start to the day.”

Robyn Haque said: “School run views, what a blessing.”

Tony Adams added: “Nice view of the London sunrise from my desk this morning!”

Why does a red sky appear at sunrise and sunset?

A red sky happens when dust and small particles are trapped in the atmosphere by high pressure. This scatters blue light and leaves only red to give the sky a beautiful vibrant appearance.

This phenomenon is often referred to as Rayleigh scattering.

During sunrise and sunset, the sun is lower on the horizon, and its light has to pass through a thicker layer of the Earth's atmosphere than when it is directly overhead. As sunlight travels through the atmosphere, it encounters molecules and small particles in the air. The shorter wavelengths of light, such as blue and violet, are scattered more easily by these atmospheric particles, while the longer wavelengths, such as red and orange, are scattered less.

When the sun is low on the horizon, its light has to pass through a greater distance of the Earth's atmosphere, and more shorter wavelengths are scattered away. This leaves the longer wavelengths, particularly red and orange, to dominate the sky's appearance. The result is the warm and vivid red, orange, and pink hues that we often observe during sunrise and sunset.

The scattering of shorter wavelengths is also responsible for the blue colour of the sky during the day when the sun is higher in the sky. This is because the shorter wavelengths are scattered in various directions, giving the sky a predominantly blue appearance.

The saying "Red sky in the morning, shepherd's warning" is based on the idea that a red sky at sunrise may indicate that stormy or unsettled weather is on the way. While this adage is a traditional weather lore rather than a scientific principle, there is some meteorological reasoning behind it.

The Met Office says: "'Red sky at night, shepherds delight' can often be proven true since red sky at night means fair weather is generally headed towards you."

The concept of "Red sky at night, shepherd's delight. Red sky in the morning, shepherd's warning" first appears in the Bible in the book of Matthew. It is an old weather saying often used at sunrise and sunset to signify the changing sky and was originally known to help the shepherds prepare for the next day's weather.

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