What weather will autumn 2023 bring?

Meteorological autumn forecast issued

By Brian Gaze

The UK seasonal forecast headline is for autumn 2023 to be milder and slightly wetter than average over the three month period.

As is expected during the autumn, a wide range of weather conditions are likely. A settled period bringing exceptional warmth is forecast to dominate the first third of September. However, through the second half of the season the expectation is for increasingly unsettled periods of weather to develop in all parts of the UK.

The current El Nino phase favours a westerly flow in the late autumn, unlike the La Nina last year which increased the chance of high pressure blocking and early season cold snaps.

Forecast considerations

The forecast was produced by looking at a number of factors, including:

• Seasonal forecast models
• Persistence patterns during recent seasons and historical analogues
• ENSO conditions
• Atlantic sea surface temperatures (SSTs)
• Solar activity
• Summer weather patterns and temperature trends
• The Weather Analogue Index (WAI) which was tracked through the summer months

Long range forecast confidence

Seasonal models and recent climatology suggest a milder than average season. Background signals are mixed, but the El Nino phase correlates with a strengthened Atlantic flow later on in the season.

The WAI has offered a mixed picture, although a number of recent years, which have brought relatively mild autumns, have ranked highly.

Therefore, although a milder and slightly wetter than average autumn is forecast, other outcomes are very possible. Long range forecasts are only intended to give an idea of very broad brush trends, such as whether a season may be wetter or drier, or colder or milder relative to the long term averages.

TWO autumn 2023 forecast

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