Pressure

[Mr Carp]

I have a very basic question that I am hoping someone can answer for me.

You often hear weather forcasters talking about high and low pressure.

At what point does low pressure become high pressure in Mb

Thanks in advance.

[BARRY]

I have a very basic question that I am hoping someone can answer for me.

You often hear weather forcasters talking about high and low pressure.

At what point does low pressure become high pressure in Mb

Thanks in advance.

think you will find (and i stand to be corrected) is this .

1000Mb or above is high pressure

999Mb or below is low pressure

[Rustynailer]

Mmmm I would love to here the correct description myself. As far as I have noticed since starting watching the weather when younger. The High pressure systems spin in a clockwise direction and Low pressure systems spin in an anti-clockwise direction, regardless of pressure as sometimes I have seen low pressures above the 1000 mark on the fax charts.

I am no expert and I fully expect correction if I have put it up wrong.

Kind regards,

Russ

Edited October 28, 2007 by Rustynailer

[BARRY]

Mmmm I would love to here the correct description myself. As far as I have noticed since starting watching the weather when younger. The High pressure systems spin in a clockwise direction and Low pressure systems spin in an anti-clockwise direction, regardless of pressure as sometimes I have seen low pressures above the 1000 mark on the fax charts.

I am no expert and I fully expect correction if I have put it up wrong.

Kind regards,

Russ

you know i think your right cyclonic & anticyclonic

[Rustynailer]

Barry.

The pressure cut off figure is the question though. All it needs is an expert/forecaster to see this post and we'll have one

Taking a guess I would say around the 1004-6 area.

Regards,

Russ

[Somerset Squall]

Well I don't know the definitive answer but I have seen low pressure with a higher pressure reading than that Rusty. If you look at the BBC pressure chart for today you can see a low pressure system in the bottom left of the chart has a pressure of 1016mb. Perhaps there isn't an exact answer and I'd guess there is probably a little overlap between pressure readings that can be found in high and low pressure areas.

[grab my graupel]

Well I don't know the definitive answer but I have seen low pressure with a higher pressure reading than that Rusty. If you look at the BBC pressure chart for today you can see a low pressure system in the bottom left of the chart has a pressure of 1016mb. Perhaps there isn't an exact answer and I'd guess there is probably a little overlap between pressure readings that can be found in high and low pressure areas.

Yes that is correct S.S. below 1016mb is low pressure

[Mr Carp]

Thank you all for your input,It has answered my question.And I have learnt something in the process

[Stratos Ferric]

Well I don't know the definitive answer but I have seen low pressure with a higher pressure reading than that Rusty. If you look at the BBC pressure chart for today you can see a low pressure system in the bottom left of the chart has a pressure of 1016mb. Perhaps there isn't an exact answer and I'd guess there is probably a little overlap between pressure readings that can be found in high and low pressure areas.

I think that's the best answer. The key point is to understand that H and L are little more than useful statements of relative difference. It's important on a chart to be able to tell whether a closed circulation is LP or HP, particularly if you're a mariner or aviator. Therefore, the answer is 'it depends'.

Here's a nice shot from one of today's FAX charts that illustrates this point well.

On the one chart, a LP with a higher core pressure than a HP elsewhere.

[johnholmes]

nice illustration and explanation there SF