Weather School Musing...Ready for Snow?
Posted: Tue Nov 23, 2010 12:02 pm
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LOOKING FOR AN IDEAL CHRISTMAS PRESENT?
How about my Weather Whys DVD or The Pocket Weather Forecaster book?
See more at the Weatherweb Christmas Shop http://www.weatherweb.net/christmasshop.htm" onclick="window.open(this.href);return false;
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Good morning everyone,
It has been some time since we saw a blast of wintry weather in November, but that is exactly what is going to happen during the later part of this week and into next.
I have to admit to becoming increasingly concerned about the potential for a spell of widespread winter weather across much of southern England, the Midlands, Wales, East Anglia, northeast England and eastern Scotland over the next 10-days. Each successive run of the computer models only makes things colder and increases the risk of snowfall.
Of course it is early days and so anything could happen to change this, but at the moment you should be preparing for an early and unusual spell of winter weather.
So, what is happening to cause this?
Well, the key lies in the area of high pressure which is building to the west of the country, and low pressure over Europe. The high to the west is what we call a ‘blocking high’ and that has disruptive the more usual west and southwest winds blowing from the Atlantic.
It has forced the jet stream southwards into the Mediterranean and is driving weather systems through southern parts of Europe. This is providing a warm air feed off the Atlantic, which then combines with the cold air feed from the area of low pressure the Baltic States. The combination of the two is the very unsettled weather which Europe is about to see.
With the winds now in the northeast cold air is draining through the British isles and Ireland. The wind is going to be coming straight from the Arctic, across Russia and Scandinavia and then onto our shores.
From time to time the low pressure over Europe will get a fresh ‘injection’ of moisture from the milder, more moist Atlantic air in the Mediterranean and this will then produce a higher risk of snow showers and more persistent snow.
This chart shows the surface pressure at 6am this morning (from http://expert.weatheronline.co.uk/daten ... 2_2306.gif" onclick="window.open(this.href);return false;) It also has the jet stream marked on it (the green and yellow shading) and you can see how this has already plunged through the Mediterranean.
Another interesting chart is the temoperature prediction from the GFS Ensemble model. This model takes lots of slightly different starting points and creates a forecast based on the resulting forecasts.
The red line on the chart (at http://expert.weatheronline.co.uk/daten ... 4_2300.gif" onclick="window.open(this.href);return false;) is the surface temperature. Notice how the model predicts it to fall below freezing up to early December, and then it gradually warms up once more (do take care with reading too much into this though, models do like to bring things back into a ‘normal’ westerly pattern the further ahead they project).
The blue vertical lines show the range of model predictions, from high to low. The closer together the blue line the more trust you can have in the forecast.
Overall the chart confirms the above prediction; falling temperatures for a period of at least 7 to 10-days.
So, it is time to wrap up warm and watch as winter arrives in the British Isles and Ireland.
It makes me cold just thinking about it!
Hope that is of interest,
Simon
LOOKING FOR AN IDEAL CHRISTMAS PRESENT?
How about my Weather Whys DVD or The Pocket Weather Forecaster book?
See more at the Weatherweb Christmas Shop http://www.weatherweb.net/christmasshop.htm" onclick="window.open(this.href);return false;
*****
Good morning everyone,
It has been some time since we saw a blast of wintry weather in November, but that is exactly what is going to happen during the later part of this week and into next.
I have to admit to becoming increasingly concerned about the potential for a spell of widespread winter weather across much of southern England, the Midlands, Wales, East Anglia, northeast England and eastern Scotland over the next 10-days. Each successive run of the computer models only makes things colder and increases the risk of snowfall.
Of course it is early days and so anything could happen to change this, but at the moment you should be preparing for an early and unusual spell of winter weather.
So, what is happening to cause this?
Well, the key lies in the area of high pressure which is building to the west of the country, and low pressure over Europe. The high to the west is what we call a ‘blocking high’ and that has disruptive the more usual west and southwest winds blowing from the Atlantic.
It has forced the jet stream southwards into the Mediterranean and is driving weather systems through southern parts of Europe. This is providing a warm air feed off the Atlantic, which then combines with the cold air feed from the area of low pressure the Baltic States. The combination of the two is the very unsettled weather which Europe is about to see.
With the winds now in the northeast cold air is draining through the British isles and Ireland. The wind is going to be coming straight from the Arctic, across Russia and Scandinavia and then onto our shores.
From time to time the low pressure over Europe will get a fresh ‘injection’ of moisture from the milder, more moist Atlantic air in the Mediterranean and this will then produce a higher risk of snow showers and more persistent snow.
This chart shows the surface pressure at 6am this morning (from http://expert.weatheronline.co.uk/daten ... 2_2306.gif" onclick="window.open(this.href);return false;) It also has the jet stream marked on it (the green and yellow shading) and you can see how this has already plunged through the Mediterranean.
Another interesting chart is the temoperature prediction from the GFS Ensemble model. This model takes lots of slightly different starting points and creates a forecast based on the resulting forecasts.
The red line on the chart (at http://expert.weatheronline.co.uk/daten ... 4_2300.gif" onclick="window.open(this.href);return false;) is the surface temperature. Notice how the model predicts it to fall below freezing up to early December, and then it gradually warms up once more (do take care with reading too much into this though, models do like to bring things back into a ‘normal’ westerly pattern the further ahead they project).
The blue vertical lines show the range of model predictions, from high to low. The closer together the blue line the more trust you can have in the forecast.
Overall the chart confirms the above prediction; falling temperatures for a period of at least 7 to 10-days.
So, it is time to wrap up warm and watch as winter arrives in the British Isles and Ireland.
It makes me cold just thinking about it!
Hope that is of interest,
Simon