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Winter 2021-22

An initial look


20/09/2021

Summary of winters since 2008

After a long run of mild winters lasting through much of the 1990s and 2000s, a run of colder winters started in 2008-09 and finished in 2012-13. Since then they have been mainly mild, although 2020-21 was slightly colder than average across the UK as a whole.

Late February 2018 brought a spell of severe wintry weather dubbed the Beast from the East, but despite that the last notably cold month was March 2013 when the mean UK temperature was 2.2C, which is 3.3C below the average. Prior to that December 2010 was the first calendar month since February 1986 to record a sub-zero Central England Temperature (CET).

The list below shows temperature anomalies in UK winter since 2008-09.

2008-09
Colder than average. The UK mean temperature for the winter was 3.2°C, which is 0.5°C below average.

2009-10
Much colder than average. The UK mean temperature for the winter was 1.6°C, which is 2.1°C below average. In many parts of the UK this was the coldest winter since 1978/79.

2010-11
Colder than average. The UK mean temperature for the winter was 2.4°C, which is 1.3°C below average.

2011-12
Milder than average. The UK mean temperature for the winter was 4.5°C, which is 0.8°C above average.

2012-13
Slightly colder than average. The mean temperature over the UK for winter was 3.3 °C, which is 0.4 °C below average.

2013-14
Much milder than average.  The UK mean winter temperature was 5.2°C, which is 1.5°C above the average.

2014-15
Close to average. The UK mean winter temperature was 3.9°C, which is 0.2°C above the average.

2015-16

Very mild. The third warmest in the series from 1910. The UK mean temperature was 5.5C, which is 1.8C above the average.

2016-17

Very mild. The UK mean temperature was 5.0C, which is 1.3C above the average.

2017-18

Close to average. The UK mean temperature was 3.6C, which is 0.2C below average. 

2018-19

Much milder than average. The UK mean temperature was 5.2C, which is 1.4C above average. 

2019-20

Much milder than average. The UK mean temperature was 5.3C, which is 1.5C above average. 

2020-21

Slightly colder than average. The UK mean temperature was 3.5C, which is 0.2C below average.

Last winter was slightly colder than the average. However, the anomaly was mostly due to colder than average conditions in the northern half of the UK.  

To summarise: Since 2010/11 there has not been a significantly colder than average winter. There were wintry spells in both 2012/13 and 2017/18 but most of the cold weather occurred in the meteorological spring and so does not impact the statistics presented here.

Berkhamsted snow, February 27th 2020

Snow in Berkhamsted, Hertfordshire on January 25th, 2021

Winter 2021-22 indicators

Last winter brought several cold outbreaks but their focus was often restricted to the north. The coldest conditions in the south occurred during the second week of February. Parts of the south east and East Anglia saw heavy falls of snow during this period, but conditions were very localised.

How are things shaping up this time?

Seasonal models

Publicly available data from most of the seasonal models goes as far as the end of January 2022.

Model Temperature Precipitation
UK Met Office GloSea (UK) D/J/F Above average Near normal
Meteo France (France) D/J/F Above average Above in the north west, below in the south. No bias elsewhere
ECMWF D/J/F Above in the south west. Mostly no bias elsewhere Mostly no bias
DWD (Germany) D/J/F Above average Below average in the southern half of the UK
ECCC (Canada) D/J/F Below average Mostly no bias. Above average in the north west
International Research Institute (IRI) D/J/F Below average in Scotland. Above average or no bias elsewhere  Above average in the west
CMCC D/J/F Above average in the south and west Above average
JMA D/J/F Mostly no bias. Above in Ireland No bias
C3S multi system (European combi) D/J/F Above average Mostly no bias. Above average in the north west
CFS v2 (USA) D/J/F Above average  Mostly above average


D/J/F = December, January, February

The Climate Forecast System v2 is available on TWO. View the latest CFS v2 charts.



Apart from the International Research Institute and ECCC all of the models listed are either showing no bias or above average temperatures. 

In terms of precipitation there is currently a signal for a wetter than average winter in much of the UK, but particularly the north west.

To summarise: At the time of publication it would be reasonable to assume that most of the seasonal computer models are favouring a winter with a mostly positive North Atlantic Oscillation (NAO) pattern. Long periods of relatively mild, wet and windy conditions would be likely.

It is important to appreciate that the skill level of seasonal models for the UK and north western Europe is low, in other words they are not very accurate.

North Atlantic Oscillation (NAO)

The NAO is essentially a measure of pressure patterns across the North Atlantic. During the winters when a negative NAO develops, blocking areas of high pressure form at high latitudes and displace the cold Arctic air down to mid latitude locations such as the UK.

This year the likelihood of a neutral or negative NAO based on the Sea Surface Temperature (SST) profile is considered to be higher than the norm.

Quasi-biennial oscillation (QBO)

The QBO index is determined by the strength and direction of equatorial zonal winds in the tropical stratosphere. When the winds are in a westerly phase the index is positive and when in an easterly phase it is negative. A correlation between the strength of the jet stream across the North Atlantic and the QBO has been identified. A negative (easterly) QBO favours a weaker jet stream which in turn means a greater chance of cold spells during the winter months.

The QBO switched back to a negative phase earlier this year and usually the cycle normally lasts for 28 or 29 months. Therefore, the current expectation is for the QBO to remain negative through the coming winter.

On balance the latest developments increase the likelihood of a colder than average winter.

Looking across the Bulbourne Valley in Berkhamsted.
Looking across the Bulbourne Valley in Berkhamsted

El Niño Southern Oscillation (ENSO)

El Nino takes place when SSTs in the central-east Pacific are anomalously warm and La Nina when they are colder than average. ENSO has an impact on global weather patterns, although the link to the UK is quite weak. A weak El Nino event is believed to increase the chance of colder weather during the second half of the winter.

Forecasting the ENSO conditions several months ahead is prone to error, but at the moment there is a 70% to 80% chance of a La Nina event persisting through the Northern Hemisphere winter. 

The TWO view is a weak La Nina increases the chance of a cold winter in western Europe. A strong event probably diminishes it.

Solar Activity

The link between solar activity and the weather remains controversial. There is a suggestion that colder winters are more likely to occur in the UK close to or shortly after a solar minimum is reached.

Solar Cycle 25 is  considered to have started between August 2019 and January 2020. There are suggestions that solar cycle 25 will be very active. However, the maximum number of sunspots in successive cycles has been declining in recent decades.

The position of the solar cycle may increase the chance of a cold winter in western Europe.



Analogue index 

This year for the first time we are running an automated system which checks the current state of the 500hPa level in the northern hemisphere and compares it with the same day for every year going back to 1948.

As of 20th September, 2021, the 5 closest matches are:

1) 1960

2) 1970

3) 2016

4) 2008

5) 2004

1960-61 was a mild winter

1970-71 was a relatively mild winter

2016-17 was a mild winter

2008-09 was a relatively cold winter

2004-05 was a relatively mild winter 

Therefore, the analogue index at the time of publication is favouring a milder than average winter.

You can view the weekly index tracker each day to see how it develops.

Summary

At the moment there isn't a definitive signal for winter 2021-22.

The seasonal models are quite bullish about it being milder and wetter than average. On the other hand, the prospects for the QBO and NAO are suggesting an increased chance of a cold winter.

The expectation of a La Nina phase may be a factor which increases the likelihood of a cold weather during the first half of the winter. The relatively early state of solar cycle 25 could also suggest an increased chance of a colder winter.  Nonetheless, both of these factors are tenuous at best.    

The analogue index top five has four members which had milder than average winters. 

Recent climatology once again favours average to milder conditions. Last winter was colder than the previous two, but the UK mean temperatures was only marginally below the average. Through 2021 warmer than average months have been more frequent than cooler ones.  

Taking the above into account the initial TWO view is that the chance of a colder season is slightly higher than it has been in recent years. However, on balance the data at this stage suggests temperatures for the December, January and February period taken as a whole are more likely to be above than below average.

Regular updates will be issued before the TWO winter forecast is released at the end of November.

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