The Winter Forecast Thread

I though a thread for posting and discussing winter forecasts, seperate to the general winter thread, might be of some use.

To start off with, here's my winter 2013/2014 forecast.



For this forecast, I looked at 10 different teleconnections for their trends and averages in the last 6 to 9 months (and forecasts for MEI), and then compared those criteria with previous years, mostly back to 1951, and created a list of the years with the most similar teleconnections to this year.


Below are the 10 teleconnections and the criteria used with them.


Teleconnections ...................... ................... Criteria


Arctic Oscillation (AO): Mean of the last 6 months (May to October) close to 0, and little month to month variation.

North Atlantic Oscillation (NAO): Mean of the last 9 months (February to October) close to 0, and a moderate to large amount of month to month variation.
Multivariate ENSO Index (MEI): Winters averaging between -0.5 and +0.5 for the October to February period.
Eurasian Snow Cover: Years that show an above average increase from September to October Eurasian snow extent.
Quasi Biennial Oscillation (QBO): Positive in Autumn and falling through Winter.
Solar Activity: An 11 year monthly sunspot mean of below 70
Atlantic Multidecadal Oscillation (AMO): Mean above average over the last 9 months.
Pacific Decadal Oscillation (PDO): Mean moderately below average over the last 9 months
Arctic Sea Ice: A September sea ice area minimum of less than 4 million km2
Globally Averaged Angular Momentum (GLAAM): Mean of the last 9 months close to 0, with moderate month to month variation.


After going through the data, these were the most closely matched year

Year ... Criteria Matches out of 10

2010/11 = 7*
2009/10 = 6
2006/07 = 6
2004/05 = 7
2003/04 = 6
2002/03 = 6
1985/86 = 6
1978/79 = 6
1976/77 = 6
1973/74 = 6


So using this, each of the years with 6 matches would get 1 place in the composite maps, and 7 matches would get 2. *An exception here is 2010/11, which had a moderate El Nino, so that will only be included once.


So based on the above, here's the winter forecast.

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DECEMBER


A strong Atlantic ridge stretching into southern Greenland, coupled with low heights stretching from Scandinavia to the Iberian Peninsula, look to be the main features for December. An increase in northerly orientated winds could be expected with this set up, but, if the trough moves much further west, the is a chance of some milder southerly winds occurring, sourced from the western Mediterranean.


Precipitation is likely to be close to average in general, but with a slightly higher chance of below rather than above average monthly totals.
Temperatures are more likely to be below average, perhaps 0.5-1.0C below the 81-10 mean.


JANUARY

Northern blocking, a west based -ve NAO and a large trough across central Europe are the main features for January. Northerly and northeasterly winds are likely to be more common during the month.


Precipitation is likely to be below average again, especially in the west.
Temperatures are likely to be below average once more, with the coldest conditions further east. Temperatures around 0.7 to 1.5C below the 81-10 mean.



FEBRUARY

While confidence is lower this far out, February looks like featuring some very strong northern blocking, centred toward Greenland, with low heights across our south and into Europe. The set up should produce much more easterly winds than normal, maintaining the cold theme and enhancing the snow risk for eastern counties.


Precipitation is likely to be close to or above average in the south and east, and below average further north and west
Temperatures are likely to be below average everywhere, around 0.8C to 1.8C below the 81-10 average.


OVERALL
Strong heights over southern Greenland should be a recurring feature of the first 2 months of winter, bring plenty of northerly airflows, before more general blocking takes hold, carrying easterly winds during February. With low heights nearby and plenty of cold sourced airflows, each month has the potential for spells of cold and snow. So while precip looks like being below average overall, snowfall totals may well end up above average.
The coming winter seems quite likely to be below average temperature-wise, with a good chance of all 3 winter months being below the 81-10 average.


If I was to guess at a period with the highest risk of severe cold, I'd say late January and early February, as northern blocking strengthens eastward and brings a more easterly flow across the country