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Global Winds and Atmospheric Pressures

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About Air Pressure

About the Prevailing Winds


 

Wide-area Coverage Charts

Atlantic Ocean - North

Atlantic Ocean - South

Indian Ocean

Mediterranean Sea

Pacific Ocean - Central

Pacific Ocean - North

Pacific Ocean - South

United States


 

Local-area Detail Charts

Bahamas

Caribbean Sea

Europe North Sea

Gulf of Mexico

Labrador-Greenland

Nova Scotia

Pacific Ocean - Canadian coast

Pacific Ocean - US coast

U.S. Great Lakes


Click on a chart to see the full website.
 
See also information on global wind patterns, atmospheric rivers, and our webpages on Winds Surface and Aloft Current and Forecast and Ocean Weather.

Wide-area Coverage Charts

United States
Atlantic Ocean - North
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Atlantic Ocean - South
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Pacific Ocean - North
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Pacific Ocean - Central
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Pacific Ocean - South
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Indian Ocean
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Mediterranean Sea
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Local-area Detail Charts

Bahamas
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Caribbean Sea
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Europe North Sea
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Gulf of Mexico
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Labrador-Greenland
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Nova Scotia
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Pacific Ocean Canadian coast
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Pacific Ocean US coast
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U.S. Great Lakes
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About Winds and Air Pressure

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Planetary Prevailing Winds
Regarding winds and the movement of air masses, the Earth can be divided into three general areas: the polar regions, the temperate zones, and the equatorial regions.
For more about prevailing winds, click here or on the diagram at left.
For an example of airflow transitioning from the equatorial zone (west-bound) to the temporate zone (east-bound), see the chart at right.
Air pressure

Air pressure is shown in millibars or inches.  The average (standard) air pressure at sea level is 1013 millibars (mb), or 29.92 inches.

Any area with a lower value is an area of low pressure.  Any area with a higher value is an area of high pressure.  The further the pressure is from 1013, the greater the speed of the associated winds.

Weather charts will often label an area as a low, even if it is above 1013 but it is surrounded by higher air pressures.

High pressure tends to bring sunny weather.

Low pressure tends to bring clouds and precipitation (rain, sleet, or snow, depending on the temperature).

Air pressure declines as the altitude rises above sea level, which means you get less oxygen with each breath.  At 11,000 feet, the air pressure is only two-thirds (670 mb), which means you are only getting two-thirds as much oxygen in each breath as normal.  At 18,000 feet, the air pressure is only half (506 mb).  These are standard values; the actual air pressures will vary, as they do at ground level.

Peoples' tolerance for getting less oxygen varies; some people can go no higher than 5,000 feet (843 mb); others can go as high as 14,000 feet (595 mb) with no problem.  The bodies of people who live at high altitudes adapt, and those people can go higher.  Vision can also be affected by high altitude, particularly at night.

The lowest pressure ever recorded (at sea level) was 867.93 millibars, in the eye of typhoon Tip over the Pacific Ocean on 12 October 1979.

The highest air pressure ever recorded was 1085.68 millibars at Tosontsengel, Mongolia, on 19 December 2001.

Inches Hg   to   Millibars   to   Altitude   conversion   (standard pressure)
29.92" = 1013 mb = 0000'       23.98" = 0812 mb = 6000'       14.76" = 0500 mb = 18,000'
28.85" = 0977 mb = 1000' 23.09" = 0782 mb = 7000' 11.81" = 0400 mb = 24,000'
27.82" = 0942 mb = 2000' 22.24" = 0753 mb = 8000' 8.86" = 0300 mb = 30,000'
26.81" = 0908 mb = 3000' 21.38" = 0724 mb = 9000' 6.64" = 0225 mb = 36,000'
25.84" = 0875 mb = 4000' 20.58" = 0697 mb = 10,000' 5.17" = 0175 mb = 42,000'
24.89" = 0843 mb = 5000' 19.19" = 0650 mb = 12,000' 3.69" = 0125 mb = 48,000'
For more about the current winds, temperatures, and moisture levels at various altitudes, see our webpage about Skew-T Log-P Charts.

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