Winter 2021-22 final pointers

Update 3

19th November 2021

Overview

For context and background information please read:

Winter 2021-22 weather, an initial look issued on September 20th 2021.

Winter 2021-22 Update 2 issued on October 29th 2021.

 

Berkhamsted snow, December 2017

Heavy snow in Berkhamsted, December 2017

September, October and November

The Central England Temperature (CET) for September was well above the 30 year average. On balance TWO considers a cooler month more likely to be followed by a colder winter.

The October CET also finished above the 30 year average. A correlation between warm and dry Octobers and colder than average winters has been discussed.

To the 18th the provisional CET for November is 2.1C above the 30 year average. 

Seasonal models

Publicly available data from most of the seasonal models covers the entire period of the meteorological winter.

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


D/J/F = December, January, February

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

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Since the second review, issued on October 29th 2021, the seasonal models have firmed up further in suggesting:

1) Above average temperatures

2) Precipitation more likely above than below the average

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)

No change from the previous update.

Quasi-biennial oscillation (QBO)

No change from the previous update.

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 90% chance of a La Nina event persisting through the Northern Hemisphere winter. The percentage chance has further increased since the previous update.

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

North Atlantic Sea Surface Temperatures (SST)

No change from the previous update.

Solar Activity

No change from the previous update.

Analogue years

The Winter Analogue Index (WAI) 60 day tracker at the time of publication has the 10 best Northern Hemisphere matches as follows: 

1) 1968 (Cold)

2) 2004 (Mild)

3) 2010 (Cold)

4) 2005 (Close to average)

5) 2013 (Very mild)

6) 1955 (Cold)

7) 1973 (Mild)

8) 2007 (Very mild)

9) 1963 (Cold)

10) 2014 (Close to average)

At this stage the WAI has an even split between cold, mild and average winters. 

Taken as is, the current 60 day tracker possibly suggests a greater chance of a cold winter than has been the case in recent years.  

Summary

Since the second update the seasonal models have firmed up further on pointing towards a mild winter in the UK. The precipitation forecast has also leaned towards a wetter than normal season.

Other factors such as NAO, QBO and La Nina are consistent with the previous update.

The 60 day WAI was not available when the second update was issued. However, it may offer weak support for an increased chance of an average or colder than average winter compared to recent years. Nonetheless, recent climatology favours milder conditions. 

Taking the above into account the current TWO view is that a milder season continues to be favoured, but there are a number of pointers which support a cold scenario.

The TWO winter forecast is released at the end of November and it will also consider how weather patterns developed during the last weeks of the meteorological autumn.

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