March – a month of weather contrasts

18 03 2013

Winter seems to have hung on for quite some time this year with low temperatures, frost, ice and snow affecting many areas into late March. This isn’t altogether unusual as we are more likely to see snow at Easter than at Christmas. However, March 2012 was very different with plenty of sunshine and temperatures into the low 20s Celsius. How come?

Well, this time last year the UK was under the influence of high pressure. This gave us clear skies, plenty of sunshine and with a light southerly breeze, temperatures that were well above average. In fact, Scotland set an all time record maximum temperature with 22.8 °C at Fyvie Castle in Aberdeenshire.

Visible satellite image from March 2012

Visible satellite image from March 2012

This year, with a strong easterly wind bringing cold air from Scandinavia and Eastern Europe, we have quite the opposite with eastern parts of the UK in particular seeing snow, ice and temperatures around 20 degrees Celsius lower.

Visibile satellite image from March 2013

Visibile satellite image from March 2013

The direction of the wind therefore plays a major part in what type of weather you and I will see, especially as we have the Atlantic Ocean to our west and continental Europe to our south and east. Different wind directions bring air with different temperature and moisture contents. Meteorologically, they are termed air masses and in March 2012 we saw a Tropical Continental air mass bringing dry and warm air from the Mediterranean. This year we have been affected by a Polar Continental air mass, bringing cold air from the east. The following video explains exactly what we mean by air masses.

With different air masses constantly affecting the UK, the weather is a particularly challenging thing to forecast, especially so in March. This is because in early spring the sun is starting to rise higher in the sky and the amount of daylight hours start to increase. This means we get more heat building up in the lower part of our atmosphere. The result is slightly more energy, which in turn can lead to heavier showers. We can also see more unstable air and more active fronts as a result of greater heating. With more moisture available in the atmosphere, we also tend to see heavier or more prolonged rainfall and if this mixes with cold air, more snowfall. It makes forecasting more complicated because the extra heat and moisture adds another aspect to the weather, which tends amplify the effects of different air masses.

You can find out more about forecasting snow on our website or on the following video:


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2 responses

18 03 2013
nuwurld

Dear Met, I know you probably think I’m a pain in the proverbial, but I need you to add a little more please, if you would be so kind.

You know by now that in my opinion, the world is entering a new regime of climate. Hence the ‘silly’ name I use. I think that current models fail beyond a few days. I would have liked some input about the Atlantic Oscillation and its loading pattern. I am aware that it has been largely negative this winter.

No mention in this report either that our prevailing wind in the UK is a south westerly. You only have to look at the trees on hills. Easterlies, north easterlies and north westerlies are NOT are usual weather direction.

The world is changing, and it is following the known and predicted solar reduction.

27 03 2013
nuwurld

Dear Met, really, really dismayed by the weather news on 25th March. It has left me with a cold, empty feeling. Perhaps fitting for the conditions.

I have tried to convey in earlier posts the threat of winter worsening. Still the news of increased winter deaths and farming hardship does not leave anything but sadness (which is, incidentally, far worse than has been reported, eg no germination, root crops rotting in the ground, fields unploughable due to the high water table etc).

Still, I’ve had to sit through the governments ‘chief scientist’ telling the UK to expect ‘more’ of this, because this is the new ‘normal’, due to ‘climate change’. Strangely not mentioning ‘warming’ and therefore ‘not’ compromising himself.

However, Lawrence McGinty, conveyed that after talking to the governments ‘chief scientist’ that this ‘climatic change’ was indeed due to our investment in accrued ‘greenhouse gases’. Now under anyone’s perception that ‘means’ ‘warming’, by definition.

Pause for breath, ’cause I’m upset now.

This is not a strike out at the Met, it’s directed at the system that controls it’s public front. I value that although some of my points are controversial, and sometimes delayed, all are posted. So I, as an individual, get to share my views with the ‘silent few’.

Anyway, back to my latest issue. I would like to point out that this is in no way personal. I like Jon Mitchell. Don’t read that any other way. But I feel his hands are tied.

Back in 2011, don’t recall exactly the date, I recall Jon saying,

“The Jet stream is back up around Shetland, because the Sun is active again ”

And that stopped me in my tracks. I was amazed. Jon knows and understands just what positions the ‘jet’!

I have also read that the Met knows and attributes the 2007 flooding to the jet stream trending south ‘ due to the extended solar minimum. From then they added the 11year (and incorrect) solar cycle to predictive models.

Now this early spring, the ‘jet’ is across the Med and North Africa.

Can I express my views again Met please.

For crying out loud, the ‘jet’ doesn’t control anything. It forms along the convergence of thermal cells and ‘streams’ down the barocline that inevitably forms between them. The position of the ‘jet’ marks the borders of major temperature zones.

Active Sun ‘inflates’ the equatorial atmosphere and therefore exaggerates the gradient down to the poles. This ‘pushes’ the cell borders poleward and ‘locks’ the jet stream in place.

Inactive Sun results in deflation and relaxation of the cell boundaries, allowing more blocking and Rossby wave looping.

I’ll go back to basics, although this isn’t ‘rocket science’.

The Polar cell is cold.
The Ferrel cell is moderate.
The Hadley cell is very warm.

Whilst the world ‘was’ warming, a decade or more ago, the jet stream was trending poleward in both Hemispheres. Increasing the size of the warmer cells at the expense of the cooler Polar cells.

Now the Jet stream in both Hemispheres is trending equatorial, reducing the warmer cell size in favour of the expansion of the cooler Polar cells. This is NOT a matter of confusion. If the cooler cells get larger, the world is cooling.

Also, as the ‘jet’ trends equatorial so does the cloud band and the less energy the Earth gets to absorb. Such is solar feedback.

This is the onset of irreversible cooling. The Sun will inflict the full effects of reduction following 2014 and will not allow any warming beyond current levels till beyond mid century.

It’s nothing to do with the stupid notion of so called ‘greenhouse gases’. Nor can it be due to the reduction of sea ice. The Antarctic has done nothing but increase.

As this cooling will prove.

This is caused by a reduction in the portion of the solar flux that the Earth equilibrates with. Full reduction starts next year with the onset of a Solar Grande Minimum.

For what we are about to receive….

Our ancestors had to deal with this some 350years ago. Will we fare better?

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