News and information

Autumn 2021 UK weather

First discussion


14/07/2021

Autumn outlook

Before looking ahead it is worth quickly reviewing the weather so far this year as well as Autumn 2020.

2021 to date

Central England Temperature (CET) has shown more variability than in 2020 when the first 6 months were all warmer than 30 year average. This year the 3 months have been colder than the norm.

Month CET Anomaly
January 3.1 -0.7
February 5.1 1.4 
March 7.2 1.5 
April 6.4 -1.5 
May 10.1 -1.0 
June 15.5 1.4 

Autumn 2020

The season was 0.5C warmer than average with a UK mean temperature of 9.9C. This contrasted with the previous autumn which was about 0.3C colder than the 1981-2000 average. 

The monthly temperatures anomalies were:

September: 0.2C
October: -0.1C
November: 1.5C

Rainfall totals were mostly within 25% of the 1981-2010 average.

Sunshine totals were 117% of the 1981-2010 average.

In recent years there has been a tendency for months to be above rather than below CET. That is a significant consideration when looking ahead to Autumn 2021. However, the temperature profile during the first 6 months of this year has been more variable than it was in 2020. 

 

Autumn colours

Autumn colours in Berkhamsted

Autumn seasonal model overview

The table below summarises output from seasonal forecast models for September, October and November 2021. It  represents the data available at time of publication and subsequent updates may favour a different outcome. 

Model Temperature Precipitation
UK Met Office GloSea (UK) Above normal Above average in the east. Below average in part of the west
Meteo France (France) Above average Above in the north
DWD (Germany) Above average Below in parts of the north
CMC (Canada) Above average in the north Below in the south west, above in the far north
ECMWF No anomaly

Below average in some southern and central areas

International Research Institute (IRI)  No anomaly Below normal more likely
JMA (Japan) Below average in the north west Above in the north
C3S multi system (European combi) Above average No anomaly
CFS v2 (USA) No anomaly

Above more likely

C3S multi system incorporates date from ECMWF, UK Met Office, Meteo France, CMCC, DWD, JMA and NCEP.

There is a signal for temperatures to be above the average. The precipitation outlook is not clearly defined.

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 considering:

1) There is considered to be a 55% chance of La Nina returning this autumn. La Nina tends to support drier conditions during the meteorological autumn in Spain and parts of France. There is also a correlation with an increased incidence of cold weather in the UK through late autumn and early winter. 

2) A more active than normal hurricane season is forecast by the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center. An active hurricane season possibly increases the chance of high pressure areas forming over Europe as storm systems track northeastwards.

3) Current high levels of global warmth.

4) Warmer than average seasons have been common in the UK during recent years. However, the temperature anomaly during the first half of 2021 has been closer to the average than has been seen in several recent years.

The above pointers do not provide a strong signal for the coming autumn. 

Summary

At this stage aggregate temperatures for the meteorological autumn (September, October and November) are considered slightly more likely to be above average than below. Nonetheless, signals are weak and the chance of below average temperatures may increase towards the end of the season.

The precipitation outlook is very uncertain. On balance wetter than average conditions are favoured during the early part of the autumn, with the increasing likelihood of it it becoming drier, relative to the norm, later on.

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.  

Press and media enquiries

We welcome all press enquiries, whether relating to this news feature, or seeking comment on other weather news.

Contact us

RECENT WEATHER NEWS


DISCUSSION

UK forecasts

14 day outlook

Monthly outlook

Seasonal outlook

COMPUTER MODELS

Fancy forecasting yourself?

Then check our huge huge range of charts and data.