Winter 2008/09 early thoughts

Introduction
TheWeatherOutlook winter forecast will be issued in late November, and will take into account a range of factors including the weather patterns which developed during the autumn. So as we

are only just over half way through the autumn it is too early for us to say what the forecast is likely to suggest, but at this juncture a few early thoughts on the winter weather are possible. Before reading on, here are a couple of caveats. Firstly, as ever remember that all long range predictions for this part of the world tend to be inaccurate and secondly, this is not intended to be a forecast.

What data is available already?
North Atlantic Oscillation (NAO) forecasts
UCL (see here)
Slightly positive, with the probabilities favouring slightly above average temperatures and close to average precipitation.

UK Met Office (see here)
Slightly positive, possibly suggesting close to or slightly above average winter temperatures and precipitation levels.

Seasonal forecast models
UK Met Office (see here)
The available data from the Met Office is pointing towards a milder than average winter. The September update shows above average temperatures across most of northern Europe (including the UK) during the winter months .

International Research Institute (IRI) seasonal charts (see here)

The charts issued this October are indicating a milder than average winter across north western Europe. They possibly suggest that any cold spells in the UK are more likely during the first half of the winter.

Pattern matching

Comparing Autumn 2007 and 2008

Comparing surface pressure and 850hPa charts with the first half of autumn 2007 and 2008.

 

September 21 2007
//theweatheroutlook.com/twodata/gfs/2007/09/21/00_0_mslp850.png

 

September 21 2008
//theweatheroutlook.com/twodata/gfs/2008/09/21/00_0_mslp850.png

Blocking further north and less cold pooling over Greenland.

 

October 1 2007
//theweatheroutlook.com/twodata/gfs/2007/10/01/00_0_mslp850.png

October 1 2008
//theweatheroutlook.com/twodata/gfs/2008/10/01/00_0_mslp850.png

Less blocking across the UK and more cold pooling over Greenland.

 

October 15 2007
//theweatheroutlook.com/twodata/gfs/2007/10/15/00_0_mslp850.png

October 15 2008
//theweatheroutlook.com/twodata/gfs/2008/10/15/00_0_mslp850.png

 

Significantly more cold pooling to the north of the UK.

The possible suggestion from these charts is that winter in the UK may arrive earlier this year.

Temperatures in the UK this year
Our own temperature index shows:

September 2008 was about 0.4C lower than September 2007
August 2008 was 0.7C warmer than August 2007
July 2008 was 1.1C warmer than July 2007
June 2008 was 1.2C cooler than June 2007

ENSO
The winter is expected to bring neutral conditions. The link between these and the winter in western Europe is tenuous, but there is a feeling that neutral conditions are less likely (than the La Nina conditions of winter 2007/08) to bring mild conditions to the UK during the winter months.

Solar activity
This is very controversial, but it has been suggested that lower solar activity leads to a less active jet stream. Recently level of solar activity (measured by the number of sun spots) have shown signs of increasing. If this is believed it may be argued that less settled and milder conditions are likely this winter .

So what about winter 2008/09?
My view at the moment is that there are some signals which indicate the possibility of colder conditions earlier in the winter than we have seen during recent years. Whether this would lead to widespread snowfall or not is a different question. In the UK the best opportunity for low level lying snow occurs between early January and mid-February. During the first half of December conditions are rarely cold enough, although there are exceptions such as December 1981.
TheWeatherOutlook winter forecast will be issued in late November. 

Issued 19/10/2008 © Brian Gaze