First Signs of Winter?

October 9, 2011

Weather Forecasts


In the past couple of days I’ve been keeping a very close eye on various different model outputs and one thing as stood out, the trend towards a Northerly incursion towards the 18th October. Now, the models haven’t exactly been progging this Northerly continuously and they have been flip flopping back and forth between colder and warmer weather, so whilst confidence on this is currently low, it is growing for colder weather to hit the British Isle from the 18th October onwards.

Lets take a look at two different weather models, first the GFS followed by the ECM

Whilst the GFS shows a more potent, severe Northerly, the ECM is forecasting a less severe Northerly, though both models are relatively similar, High Pressure in the Atlantic and Low Pressure to the North-West of the United Kingdom drawing in colder Northerly air. The Ensemble members are also showing a cool down after an initial warm up later this week

The Ensemble Chart above shows us both temperature and precipitation predictions. The top set of lines shows us the temperature variations between different ensemble members within the run, the closer together these lines are, the more confidence there is. As we can see, the lines are fairly packed together at the beginning and remain fairly close together until around the 17/18th October, which is when things begin to cool down, thats when the pack splits and varies. At the same time, at the bottom we see an increased amount of lines, these are known as Precipitation spikes and suggest wetter, unsettled weather.

Weather Forecast:

After a brief warm up as we move through this week and into the weekend where temperatures are likely to recover once again to the low 20’s, low Pressure will slide Eastwards across the North of Scotland and into Scandi on Sunday/Early next week, at the same time, High Pressure will begin to develop in the Atlantic introducing a colder North-West/Northerly airflow. Just how cold this airflow is likely to be remains to be seen, however its likely that the Scottish mountains will see some snowfall, everywhere else is likely to see rain.

Beyond the 18th/19th after the cool down, the forecasting period becomes a little more difficult, although it does seem increasingly likely that we’ll see a spell of cool, wet weather with low pressure systems coming down from the North-West bringing spells of wintry weather across Scottish Mountains, and rain to other areas of the UK. I’ll be monitoring the situation in the coming days and will issue an update when things become clearer.
Beyond

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