TheWeatherOutlook winter forecast for 2012/13 will be issued in late November and made freely available on the site. It is based on a number of factors such as weather patterns during recent seasons and those which develop through the autumn. At this juncture it is too early to confidently say what the winter forecast will suggest, but a few early thoughts are possible. Before reading on, remember the caveats. Firstly, long range weather predictions for this part of the world tend to be inaccurate, and secondly, this is not the TWO winter forecast.
Seasonal forecast models
A number of seasonal forecast models are available, but my view is they often aren’t accurate, and I view them as just another input into the forecast. I’ve looked at the output from the International Research Institute (IRI), Coupled Forecast System (CFS), ECM seasonal model, UK Met Office, Meteo France, JMA and IOD.
The model outputs are updated at regular intervals, and tend to be expressed in terms of anomalies for temperature, pressure and precipitation. I won’t discuss them in detail here, but in general terms they seem to be more promising than last year if you're hoping for a cold winter this year. One thing I have noticed is that the latest updates from a couple of them while still suggesting the risk of a cold winter, have started reducing the probability of this outcome. The updates in the next 6 weeks will be interesting.
No strong signal, but leaning towards a colder and possibly drier than average winter across all parts of the country.
As we’re only half way through the autumn it is too early to draw conclusions here. However, there have been continued suggestions of northern blocking, with signs of disruption to the vortex over Greenland.
At this stage it looks more favourable than at the same point last year, with the possibility of a disrupted Atlantic flow at least early in the winter, allowing colder weather from the north or east (Scandinavia) across the UK.
The winter is expected close to neutral ENSO conditions.
No strong signal.
Currently the SSTs are favourable for northern blocking to develop. However, the May SST signal was indicating that a positive North Atlantic Oscillation (NAO) was the most likely outcome this winter. A link between the May SST profile and the NAO of the following winter has been established, so this should not be ignored.
Possibly favouring a milder outcome.
Solar activity has increased recently, although it is still relatively low for this stage of the cycle.
Less favourable to cold conditions than a couple of years ago, although this is controversial.
Other teleconnections (pressure patterns)
In addition to the NAO, a number of other teleconnections are often considered when making long range forecasts, often relating to pressure patterns in the Pacific region and how these could be changed by ENSO and the Madden-Julien Oscillation (MJO).
No strong signal for forecasting.
Stratospheric temperature forecasts
In simple terms stratospheric warming is believed to encourage northern blocking. The problem is forecasting stratospheric temperatures, and fully understanding the time lag and how to use this as a forecasting tool for a small part of the Earth such as the UK.
Whilst I'm interested, I don't currently think it's possible to draw conclusions in this area, so to me there is no strong signal.
Summer 2012 was quite cool and often wet, but winter 2011 - 12 was mostly mild unlike the three previous winters.
Car in snowdrift
Cold winters do tend to come in clusters, but even during these periods mild winter do occur. We may well still be in a period when the chances of a particular winter being cold are higher than average.
The wet summer and coolish summer and the weather patterns of recent years are mildly favourable for a cold winter this year.
So what about winter 2012/13?
It's still early to make a call and I'll not do that at this point. Again I would say things are finely balanced, but the chances of colder than average conditions during the December, January and February period are higher than they were at this time last year. At this stage I'd not rule out throwing a curve ball and calling a very cold winter, but lets see what the rest of October and November brings. TheWeatherOutlook winter forecast will be issued in late November. On the basis of this discussion, don’t conclude what it will be predicting because how the weather evolves during the next six weeks is a very important consideration for me.
Issued 09/10/2012 © Brian Gaze
http://www.theweatheroutlook.com/twooth ... bg&id=1869