Cold Weather Update 6

November 19, 2012

Weather Forecasts


It seems like we’ve been talking about this for weeks now but I think the models might finally be starting to firm up on the general pattern expected for the end of the month. There’s still a lot of uncertainty over the details and specifics and I think it’ll be a while yet before these become clearer so I’m going to avoid talking about the operational models, but instead in this update focus on the height anomaly charts as these tend to give a more accurate picture.

Lets start by taking a look at the GFS & ECM 500hPa Height Anomaly charts

The chart above tells us that whilst details differ slightly between the two models, there is a definite signal for high pressure building in the Atlantic and across Greenland with low pressure being pushed to the South and East of the United Kingdom giving us quite a blocked pattern.

Next we’ll take a look at the NAEFS Height Anomaly model

Much like the first chart I posted, we can immediately see that there’s a signal for high pressure to the North-West of the United Kingdom over Greenland extending down into the Atlantic, this again forcing lower pressure to the South of the UK leading to a blocked pattern.

The NAO and AO are forecasted to move into negative territory but at the moment there is a lot of ensemble scatter making it incredibly difficult to see just how negative these indices are likely to go.

So whilst there generally is teleconnective support for what the Height Anomaly charts are showing, the setup for the end of the month continues to be very uncertain as to how cold its actually going to get.

The key things at the moment are:

  • Low Pressure pushing South-Eastwards into Europe
  • High Pressure builds across the Atlantic, Greenland and Scandinavia
  • High Pressure over Scandinavia pushes West towards Greenland in response to low pressure pushing South-East

There’s a very strong signal for the above to happen now. However I don’t think it’s going to be a quick route to cold, temperatures look likely to cool off gradually as colder air slowly works its way into the mix. As for snowfall? At the earliest we’re looking at the end of the month and into early December, providing this trend continues and nothing goes wrong.

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7 Comments on “Cold Weather Update 6”

  1. Lee Says:

    Brilliant weather website!!! Bean check it since 2010.
    Looks like there are pointers towards another winter like 2010/11.

    Keep up the great work Daniel.

    Reply

  2. lisa Says:

    wud luv to see a bit of snow dis winter:)

    Reply

  3. Jack Keegan Says:

    Just looking at the JAMSTEC DJF 2012/2013 and that looks decidedly unfavourable for a very cold winter would be nice to hear your ideas on the model Daniel

    Reply

    • Daniel Smith Says:

      Definitely a downgrade on previous updates – I tend not to take seasonal models too seriously, background signals are still pointing towards a colder than average winter!

      Reply

  4. Luke Storey Says:

    I’ve been watching the GFS Model for a week or so now and its now quite consistently pointing toward a cooler theme – which is strange because usually models like to jump to more extreme conclusions, the further the time scale ahead it is. I think the only thing that is uncertain now is where the cold will be, how intense it will be, and how much the NAO and AO go into negative integers (if the current models are correct)… I just hope we can keep a block long enough for some sustained cold like 2010.

    Reply

  5. Jack Keegan Says:

    Well make of this what you will but TWO are forecasting snow for SW London on the 27th I will let you know if that little gem actually happens. I have plenty of salt at home so I will be able to eat my hat if it does šŸ˜‰

    Reply

    • Daniel Smith Says:

      The TWO forecasts are completely computer generated unfortunately so they change as often as the models do – Having said that, in the past couple of runs there have been some minor upgrades for snow risks next week!

      Reply

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