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The 528 Thickness Line - again!

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The 528 Thickness Line - again!

Old 9th Dec 2008, 09:46
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The 528 Thickness Line - again!

It's that time of year again when the 528 thickness line appears around Europe on the forecast surface charts - or at least those produced by the UK Met Office.

But can anyone explain why the thickness lines only appear on the charts valid for 36hrs or more ahead and not on the current ones when there are patently signs that they would be there if 'enabled'.

The Uk Met Office website only explains what they are and not when, in time, they will appear.

Cheers all
mcdhu
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Old 9th Dec 2008, 14:11
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Warning Toxic!
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Someone's got to ask. What is the '528 thickness line', and would I know it if I saw it. Come on- I want a diagram with a Dibnah-like 'demonsteraertion'!
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Old 9th Dec 2008, 14:53
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According to metoffice website:

Thickness lines
Pressure decreases with altitude, and thickness measures the difference in height between two standard pressure levels in the atmosphere. It is proportional to the mean temperature of this layer of air, so is a useful way of describing the temperature of an airmass.

Weather charts commonly show contour lines of 1,000-500 hPa thickness, which represent the depth (in decametres, where 1 dam = 10 m) of the layer between the 1,000 hPa and 500 hPa pressure levels. Cold, polar air has low thickness, and values of 528 dam or less frequently bring snow to the UK. Conversely, warm, tropical air has high thickness, and values in excess of 564 dam across the UK often indicate a heatwave.
As to the original question - not a clue!
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Old 9th Dec 2008, 15:03
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With that new knowledge I dash to the met charts and hey presto it'll snow from Wednesday p.m. until Friday a.m. from BHX eastwards. Now where did I put that seaweed.
No idea what the answer to the original question is though.
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Old 9th Dec 2008, 15:15
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Perhaps the 528 thickness lines appear when the Met
people are, shall we say, making a bit of a GUESS?
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Old 9th Dec 2008, 15:27
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...making a bit of a GUESS?
IE; aka, forecast.
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Old 10th Dec 2008, 08:32
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OK, I give up. I'll try to contact the Met Office at Exeter - not holding my breath!

Cheers
mcdhu
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Old 10th Dec 2008, 09:49
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Do so, they are very helpful. They answered my last question very quickly.
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Old 11th Dec 2008, 07:34
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You're spot on there Lurkio! Here's their reply:

The reason is a historical one, and we have never done it before T+36. It is only now that the charts are broadcast on the web that people notice that some things are not there , like the thickness lines at T+24.

I will pass on your comments to our developers and forecasters and see if they can change it in the future.

I hope this helps.
Cheers all
mcdhu
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Old 12th Dec 2008, 09:23
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411A
IE; aka, forecast.
aka: What would have happened if what did happen didn't!
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