The Basics of Our Weather

The Basics of Our Weather


This lesson will discuss the basics of how our weather systems work.  

As the old adage goes, “Know Your Enemy”.  That’s what this lesson is going to teach you.  Now I’m not saying anything against Mother Nature – but every now and then, she can act up, and when she does – You Better Be Ready!

So it just makes sense to have a basic understanding about how our weather systems work.

You will need this knowledge in order to understand the workings of Hurricanes, Tornadoes, Storms, etc.  Because when one of these Bad Boys come knocking at your door, he is going to be putting a mean hurting on you – maybe even kill you.

With keeping to our philosophy of “Your Time is Valuable” and that we will not waste it; we will be discussing only the foundations here.  We have no intentions of turning you into a Great Weather Wizard, but what we do want you to know is:

  • What you are dealing with
  • What you should be looking for
  • Why you should prepare

Your primary focus should be in how you will use this information to protect your family.

So with that said, let’s start talking about how our weather systems work.

How Our Weather Systems Work


Our weather system in its simplest form; is the result of the sun’s rays warming and cooling (day and night) the water vapor that is present in our atmosphere.


Note: There are many other factors that have an impact on the weather like; the topography of the land, friction, altitude, etc. But we will not go into that – Remember: Just Keeping it simple.


Weather-Patterns-Page--OptimizedBasically, our weather patterns come from the vertical movements of air caused by the air warming or cooling and the rotation of the Earth.   As air rises, it cools at an approximate rate of 3 to 5 degrees for every 1,000 feet of altitude.  As the air cools, the water vapor present in the air may start condensing which may form clouds and precipitation: rain and/or snow.  This would be a LOW Pressure System.  Low pressure systems are usually associated with your cloudy, rainy, stormy types of days.  The water vapor is being squeezed out of the air by the cooler temperatures.

When the air becomes heated, it becomes drier and starts to fall back to the surface of the Earth.  When this type of air movement is going on, it is called a HIGH Pressure System.  High Pressure systems are associated with sunny and nice days.  The water vapor in the air is changing from a solid state to a gaseous state by the warmer temperatures.

Barometric Pressure:  Why is it Important.


Now this may be hard to believe, but air does have weight, and it can be measured with a barometer.  It is difficult to control air in a container and weigh it.  So a barometer measures the force that the air (the atmosphere) is putting on a surface.


  • The higher the Atmospheric Pressure, the more the pressure on the surface, the higher the mercury will rise inside the tube [the barometer].
  • Lower Atmospheric Pressure will put less force on the surface, causing the mercury level in the tube [the Barometer] to fall.

Weather-Basics-Web-Page-Bar-OptimizedAir pressure is important to know because it indicates if you are “in” (or “moving into”) a HIGH Pressure system or “in” (or “moving into”) a LOW Pressure system.  Remember from the discussion above:

  • HIGH Pressure systems are nice days while
  • LOW Pressure systems are the stormy days

A pressure reading above 30 inches of Mercury* indicates a HIGH Pressure System.

Pressure readings below 30 inches of Mercury* indicate a LOW Pressure System.

*Both of these readings are based at Sea Level.  Altitude does have an impact on air pressure.  The higher you go – the lower it gets – and vice versa.

It is important to know which direction the Air Pressure [Barometer] reading is moving, (trending).  You want to know:  Is the air pressure trending (UP or DOWN)?

•   If the barometer is trending in a higher direction (UP) that indicates you are in a HIGH Pressure system and the weather should be nice.

•  But if the barometer is trending in a downward direction that indicates a LOW Pressure system is coming in and that a storm may be developing in your area.

•  Be careful when the barometric pressure starts falling below 29.50 inches because that usually indicates a strong storm is developing.


Side Note: The lower the barometric pressure – the stronger the storm. The lowest barometric pressure reported for Hurricane Katrina 2005 was 26.64 inches. Rita in 2005 was 26.35 inches. And the winner is Hurricane Wilma in 2005 that had a barometric pressure of 26.05.


What Causes Wind


Wind is caused by the balancing of the air pressure difference between the different pressure systems.   (READ:Air moves from the HIGH PRESSURE SYSTEM to the LOW PRESSURE SYSTEM.)   The greater the differential – the greater the wind. See diagram above that illustrates “Vertical Air Movement”.

Temperature accounts for air movement “vertically”.

But “horizontal” movements of the air masses are influenced by the rotation of the Earth, which impacts the horizontal directional flows (currents) of both air and water, and is known as “The  Coriolis Effect”.  The Coriolis Effect gives air patterns, ocean currents and storms their cyclic patterns and movements around the planet.  It is the reason why storms in the Northern Hemisphere rotate counterclockwise and in the Southern Hemisphere rotate clockwise.

Here is a good video clip from Keith Meldahl that illustrates “Global Atmospheric Circulation”.  Global Atmospheric Circulation

I don’t want to get real technical with the physics behind this, but if you want to learn more about The Coriolis Effect, please click on this link:    The Coriolis Effect

Air movement, Water movement, Weather System movement all come down to the vertical movements of air caused by the air warming or cooling and the rotation of the Earth.  This all creates High Pressure Systems and Low Pressure Systems.  And with Mother Nature being that she likes everything to be balanced, our weather systems results from the constant balancing of these High and Low Systems.  Lo-Hi-Diagram-Optimized

OK, enough with the technical details.  I wonder how many people fell asleep in this section.  I know I did and I was writing it.  But it is fundamental information that will help you understand our weather systems.


This is what you should be taking away from this module


  1. Our weather patterns come from the vertical movements of air caused by the air warming or cooling and the rotation of the Earth.
  2. High Pressure Systems indicate nice
  3. Low Pressure Systems indicate stormy
  4. The trending direction (Up or Down) of a barometer can be used to tell us if we are moving into a HIGH or LOW Pressure System.
  5. High Pressure System is usually above 30” of Mercury – Nice Weather
  6. Low Pressure System is usually below 30” of Mercury – Stormy Weather
  7. The LOWER the Barometer reading – the stronger the storm
  8. Wind is caused by the balancing of Air Pressure Systems:  From HIGH to LOW.

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