Autumn 2023 weather prospects

First look at the meteorological autumn

By Brian Gaze

Autumn outlook

Before looking ahead it is worth quickly reviewing the weather so far this year as well as Autumn 2022.

2023 to date

The Central England Temperature (CET) has consistently been above average so far this year. June was a record-breakingly warm month.

Autumn 2021 and 2022

The UK mean temperature for Autumn 2021 was 10.9C which is 1.4C above the 1981 - 2010 average.  

Autumn 2022 was the UK's third warmest going back to 1884, with only 2006 and 2011 being warmer. The provisional UK mean temperature value is 11.1C, which is 1.4C warmer than average.

The monthly temperature anomalies were:

September: 0.5C
October: 1.8C
November: 1.8C

The UK rainfall total relative to the 1991- 2020 average was 119%. The monthly statistics were:

September: 111%
October: 115%
November: 130%

Sunshine totals were 100% of the 1991-2020 average. The monthly statistics were:

September: 92%
October: 114%
November: 95%

In recent years there has been a tendency for months to be above rather than below CET and that trend has continued through 2023 so far.

Autumn seasonal model overview

The table below summarises output from seasonal forecast models for September, October and November 2023. It  represents the data available at time of publication and subsequent updates may favour a different outcome. 

C3S multi system incorporates data from a range of sources including: ECMWF, UK Met Office, Meteo France, CMCC, DWD, JMA and NCEP.

There is a strong signal for temperatures to be above the average. The precipitation outlook is less clearly defined, but there are indications of it being wetter than average in parts of the UK.

The relationship between autumn and winter has been discussed before. There are suggestions of a correlation between warm autumns and mild winters. 

Background signals

In addition to the seasonal models a number of key points are worth mentioning:

1) There is a 90% chance of El Nino conditions continuing through the autumn and winter months. El Nino increases the chance of mild and windy conditions towards the end of the meteorological autumn and start of the winter. 

2) A close to normal hurricane season is forecast by the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center. This suggests an increased likelihood of fairly typical conditions across the North Atlantic.

3) Current high levels of global warmth.

4) Sea Surface Temperatures (SSTs) are mostly well above the normal in the North Atlantic and around the UK. Although significant changes are possible in the intervening period, the likelihood is that it will continue to be the case as we head into the meteorological autumn. Therefore, the chance of above average temperatures is increased.  

5) Warmer than average seasons have been common in the UK during recent years. All months so far in 2023 have been warmer than the average. In 2022 only December was colder than average.

The above pointers suggest a high chance of warmer than average conditions through the autumn. 

Summary

At this stage aggregate temperatures for the meteorological autumn (September, October and November) are considered significantly more likely to be above average than below. 

On balance, wetter than average conditions are favoured in the north. In the south things are quite evenly balanced between wetter and drier than average conditions.

There will be more seasonal computer model runs in the coming weeks and another update will be issued before the autumn forecast is released at the end of August.  

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