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wanzelbin

Guidance on some basics

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I posted this on the Model Discussion thread a few days ago, but I didn't get a reply - guess I should have put it on here. 

Hope someone might be able to straighten out some of my ideas below.

 

Many thanks

 

Ditto. -16 inside the Barracks corridor.Breath froze.

When I mentioned in reply to SMs post that we could dream of a link between our Atlantic ridge and the Arctic high, I was thinking further down the line in output not the 06z

gfsnh-0-288.png?6

Hi

I read lots of the posts on here, year after year, and regularly get caught up in the excitement, but despite having tried going through the nw guides (unfortunately a lot of broken links), wikipedia etc I still struggle to understand the detail of what's going on. 

The terminology is tricky and mostly learnt (probably not correctly) from context - e.g. I think a "ridge" is a line of high pressure while a "trough" is an area of low pressure - but what would be really, really fantastic is if someone could use something like the chart above and explain why it would be so great for there to be a "link between our Atlantic ridge and the Arctic high" as winterof79 says above. Also, why is one called a "ridge", and one termed as a "high"? If these high pressure areas linked, this would increase the potential for cold in the UK? Is this something to do with "blocking"? This seems to be where a high pressure system holds up or directs the movement of a low pressure system, or vice-versa perhaps?

As I understand it, a high pressure area will be pushing air down and out across the earth's surface - if this is in the polar regions, this is especially cold air, which is then sucked up by the moister slightly warmer and lower pressure area over the UK which might provide snow?

Also, the colours on the chart - am I right in thinking this is something to do with DAM - the height above sea level at which pressure is 500 mb? If so, what does the purple spot over the Baltic Sea mean? On the colour chart this would be approx 510. Does that mean the pressure is 500 mb at 510 metres(?) with a surface level pressure of 1005 mb (judging by the numbers on the isobars)? So pressure is reducing quickly as you go up where there is a low DAM value? And that means what?

I'm obviously building assumptions on assumptions, some of which are probably embarrassingly wrong. As I say, I've tried various resources to learn more, but it's very difficult without relevant examples. I hope this is considered acceptable for the modelling forum as it refers to current charts, but it would enormously help a very interested but struggling observer should anyone be able to provide a little insight.

Many thanks

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1 hour ago, wanzelbin said:

I posted this on the Model Discussion thread a few days ago, but I didn't get a reply - guess I should have put it on here. 

Hope someone might be able to straighten out some of my ideas below.

Many thanks

Understandably the terminology that is given on the forum could indeed be very confusing - I sometimes am also confused by some terminology even though I have been around in the weather for quite some time now!

Often some terms are used interchangeably (for example ridge and high pressure area). The meaning of some of these words is also not very clear. For example, a 500 hPa ridge is high pressure at the 500 hPa height surface. And a ridge at the surface is just a high pressure area at the surface. More often than not (me included) the exact meaning is not given, but can be deduced on the post itself based on experience.

For your question regarding DAM-values, I would suggest reading this guide from John Holmes:

And for the GFS chart:

 

 

EDIT: I see the links above contain documents which contain a broken link. The links (when they were available) contained very useful and easy-to-understand guides.

I'll try to go into somewhat more detail regarding these terms later today or tomorrow if needed. Maybe John Holmes would be able to supply the documents in the links above?

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Thanks very much for responding.

As you say, unfortunately a number of the links in the guides are broken. This afternoon I found this link for info on the DAM stuff - http://weatherfaqs.org.uk/node/152. I haven't read it all yet (supposed to be working :-) ) but it looks pretty thorough.

Any more help on the terminology, blocking etc would be great.

Thanks again

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I need an explanation! I had a thunderstorm yesterday here in Limousin France that culminated in a blinding flash outside my front door and an explosion that hurt my ears. My lightning protector tripped and could be reset for the electricity but my phone has died although the line seems active when called. What would cause such an effect? Was it a direct strike - there's no evidence of that - or some EMP from a strike? I'm not imagining this as all my neighbours were out after hearing the explosive bang. Local shops and the Post Office had to close due to loss of telecoms but not power...it was very scary but I respond practically but don't understand the physics.

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Come on guys, I need an answer even if you have to consult specialists...

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