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Re: [Phys-l] atmospheric highs and lows



JD gave the reason why Highs are ignored by the public - boring weather. However, Highs do exist and can be sustained over long periods - the classic example is the Bermuda High that occurs off the East Coast for long periods. The surface highs are the result of a counter-clockwise bending of the Jet Stream - resulting in increased vorticity of the jet stream air and convergence aloft (skater pulling in her arms). This converging air descends - giving us the surface high. This air warms as it descends so there is no condensation - fair weather. As long as the Jet stream stays in place, the high will sit in position on the surface. Likewise, lows are found where the Jet Stream turns clockwise - decreased vorticity and divergence (like the spinning skater) aloft and convergence at the surface (a low pressure system) to feed the upper level divergence. These are just rules of thumb - as said, real weather is amazingly complicated. However, if you look at a surface weather map, highs usually occur between lows, and vice versa.

Bob at PC

________________________________________
From: phys-l-bounces@carnot.physics.buffalo.edu [phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Bernard Cleyet [bernardcleyet@redshift.com]
Sent: Sunday, June 27, 2010 7:57 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] atmospheric highs and lows

I was telegraphic -- I meant > the P part of STP, i.e. 1013 mb, and sure enuf two places w/ 1016. And JD succinctly stated my thought, i.e. a high doesn't exist, so I thought, as it dissipates rapidly.


bc meteorologically challenged.



On 2010, Jun 27, , at 12:45, John Denker wrote:


For example, if you look at the current Significant
Weather chart
http://www.av8n.com/fly/sigwx0000-28jun10.gif
you can see big blue capital H symbols, representing
high pressure.

To a first approximation:

Surface low pressure areas tend to pull themselves
together, resulting in tight, almost pointlike cyclones
and sharp, almost one-dimensional weather fronts,
hence strong winds. They are associated with rising
air, hence clouds and bad weather.

Surface high pressure areas tend to spread out, so
they tend to be large and diffuse, with light winds.
They are associated with descending air, hence clear
skies. They are of more interest to weather mavens
than to the general public.

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