By Brian Gaze
For context and background information please read:
Winter 2022-23 weather, an initial look issued on September 30th 2022.
Winter 2022-23 Update 2 issued on November 4th 2022.
Heavy snow in Berkhamsted, December 2009
The Central England Temperature (CET) for September was above the 30 year average. On balance TWO considers a cooler month to be more likely to be followed by a colder winter.
The October CET was well above the 30 year average. Taken across the UK it was provisionally the 7th warmest on record. It was also quite a wet month with the UK recording 115% of average rainfall.
A correlation between warm and dry Octobers and colder than average winters has been discussed. Warm and wet ones do not fit into this bracket.
The provisional November CET to the 22nd of the month is 9.8C which is a massive 3.3C above the norm. It has also been a very wet month. A correlation between cold and wet Novembers and colder than average winters has been discussed. Warm and wet ones do not fit this bracket.
Publicly available data from most of the seasonal models covers the entire period of the meteorological winter.
D/J/F = December, January, February
The Climate Forecast System v2 is available on TWO. View the latest CFS v2 charts.
Since the second review, issued on November 4th 2022, the seasonal models have firmed up in suggesting:
1) Above average temperatures with the exception of the IRI which appears to have moved towards a colder scenario
2) Mostly no bias for precipitation levels, although a couple of the models have moved towards favouring drier than average conditions in much of the UK
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.
No change from previous update.
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 76% chance of 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. However, in general terms La Nina is believed most likely to increase the chance of cold snaps during the early part of the winter.
SSTs around the UK are above the norm. This will increase the likelihood of above average temperatures and help to make northerly air streams less cold than would otherwise be the case.
No change from previous update.
The Winter Analogue Index (WAI) 30 day tracker at the time of publication has the 10 best Northern Hemisphere matches as follows:
1) 2014 (Close to average)
2) 1999 (Mild)
3) 1984 (Very cold)
4) 2018 (Mild)
5) 2005 (Close to average)
6) 2011 (Mild)
7) 1989 (Very mild)
8) 1997 (Mild)
9) 2019 (Mild)
10) 2000 (Close to average)
At this stage the WAI has a bias towards milder than average winters.
Since the second update the seasonal models have not changed a great deal in terms of temperature and continue to favour a milder than average winter in the UK. The precipitation signal is very weak but there has been a slight move towards drier than average conditions.
Other factors such as NAO, QBO and La Nina are consistent with the previous update.
The WAI also offers support for a milder than average winter.
Recent climatology favours milder conditions. All months so far this year have produced positive temperature anomalies and winter 2021-22 was mild. November has been notably mild despite cooler conditions after mid-month.
The TWO winter forecast is released at the end of November.
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Key forecast charts
See the Model inventory for the full list of model charts and data