Can someone explain why in the northern hemisphere winds blow in opposite direction around low and high pressure. I have quoted it below.

 

Currently reading the PPL on the meteorology!

 

This deflection is a major factor in explaining why winds blow anticlockwise around low pressure and clockwise around high pressure in the northern hemisphere and visa versa in the southern hemisphere. Without the Coriolis effect air would simply flow directly from areas of high pressure to areas of low pressure.

The Earth spins in one direction, but the atmosphere in the southern hemisphere is (in effect) upside down when compared to the northern hemisphere. This means that the effect is completely reversed. To look at it another way....if you could look down on the north pole of the planet, you would see it spinning in an anti clockwise direction. However, if you then switched vantage points so that you were looking down on the south pole, you would see it spinning in a clockwise direction.

Hi chris! Yeh i understand that but my point is why in a low pressure system winds blow anto clockwise and in a high pressure system winds blow clockwise in the northern hemisphere

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As said above the spin of the earth and also it's effect on gravity, storms migrate away from the equator and never cross it. And this is also why you see many hurricanes being "born" near the equator.

 

For example, if you stand directly on the equator your weight is slightly less compared to standing slightly off of it. Even a few inches (TRUE!)

I saw a film of someone in Africa near the Equator, he poured a bucket of water down a funnel, it drained through anti-clockwise. Then he walked a few hundred yards South and poured a bucket into another funnel, this time it went clockwise. Now I know that's supposed to happen when well into each hemisphere, but...

I saw a film of someone in Africa near the Equator, he poured a bucket of water down a funnel, it drained through anti-clockwise. Then he walked a few hundred yards South and poured a bucket into another funnel, this time it went clockwise. Now I know that's supposed to happen when well into each hemisphere, but...

 

That's a fakery: http://www.ems.psu.edu/~fraser/Bad/BadCoriolis.html (read: Fakery of the first water) :smile:

My question is can someone explain why two pressure systems in the northern hemisphere (low and high) the winds go in the opposite way. (Low pressure, winds spin anti-clockwise)

(High pressure, winds spin clockwise)

nice link! thanks.

Maybe it's because the high pressure presents the "funnel" upside down Vernon?

My question is can someone explain why two pressure systems in the northern hemisphere (low and high) the winds go in the opposite way. (Low pressure, winds spin anti-clockwise)

(High pressure, winds spin clockwise)

Because in the northern hemisphere, you will have a lesser and lesser west to east component the farther north away from the equator you stand, due to the earth being widest at the equator. So if a parcel of air is moving north towards a low, it will appear to turn to the right relative to the ground because it has a greater eastwardly component from having started its journey where the earth is rotating eastward faster. Apply this to all parcels of air moving towards a low from all directions, it will cause the air to flow in a counter clockwise direction around the low.

This is courtesy (made in picture form) of a symposium called "Weather for Dummies" at the IMC club pavillion at Airventure '14 by Radek Wyrzykowski.

 

All weather can be described in one word - HEAT. This symposium did not bring up anything scientific but rather in picture form and the relationships of heat towards weather. (For Dummies)

 

It starts out that air temperature at higher latitudes is colder because the effective heat from the Sun takes longer to travel through the atmosphere and therefore cools. Given a fixed volume, warm air has less density therefore less pressure, hence Low Pressure. Cold air wants to warm while warm air wants to cool, this gives its natural flow. Then from what Kevin said above comes into play. From there a picture tells it all. One of the best symposiums attended at Airventure.. 

 

My question is can someone explain why two pressure systems in the northern hemisphere (low and high) the winds go in the opposite way. (Low pressure, winds spin anti-clockwise)

(High pressure, winds spin clockwise)

 

 

Ok Vernon... Here's my 'very limited' understanding.

 

Two forces... pressure gradient force (PGF) and the Coriolis force (CF).  You know the PGF is acting from the High to the Low pressure area.  So the winds want to move 'in that direction' as you said.  But Coriolis in the northern hemisphere is deflecting air to the right.  Ok so far.

 

Apparently around the Low... there's an imbalance between the Coriolis & PGF (I do not know why).  The inward acting PGF is (apparently) greater than the outward acting CF - so that the net force acts inward (a centripetal force) causing the winds to parallel the isobars. In the High it is just the opposite; the inward directed CF is greater that the outward acting PGF.

 

Have a look here - under "Movement Parallel to Curved Contours"

http://www.met.tamu.edu/class/atmo202/WindandPressuredir/wind-press-stu.html

 

Another link:

http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/fw/grad.rxml

(Gradient Wind)

Here are two videos that may shed light on the coriolis effect. The first one is about the coriolis effect in general (look in particular at the stuff before the pendulum)  and the second one about its effect on weather.

 

https://www.youtube.com/watch?v=49JwbrXcPjc

https://www.youtube.com/watch?v=i2mec3vgeaI

 

Cheers,

Peter

Thanks for the help guys, its a tricky thing to learn but really interesting maybe i should of paid more attention at school haha!

Thanks peter i'll have a look!

Also what i'm struggling with is, they mention low pressure is when warm air is rising but i also read low pressure is when its cold because the cold makes the isobars closer together and making the air more denser?

 

So how is this possible?