Junior Cycle Geography CYCLONE Atmospheric Weather on a Weather Map 992
The lines used on a weather map to display atmospheric pressure are called isobars . These connecting lines show areas experiencing similar atmospheric pressure.
999
‘H’ is used to show areas of high atmospheric pressure . ‘L’ is used to show areas of low atmospheric pressure .
The number indicates the pressure in millibars. Anything greater than 1013 mb is considered high pressure. Anything below 1013 mb is considered low pressure.
1008 TODAY, TUESDAY
Atmospheric Pressure and the Weather Low and high pressure affect the weather.
Low Pressure and the Weather
Wind: Quite strong. Indicated by isobars that are close together.
Cloud: Significant cloud cover.
Precipitation (any type of rain, hail, sleet or snow): High levels of precipitation, e.g. rain.
1029 1000 1004 1008
High Pressure and the Weather
Wind: Light. Indicated by widely spaced isobars.
Cloud: Little or no cloud cover. Precipitation: Little or no precipitation. Weather is mainly dry.
MIDNIGHT 7. High and low pressure on a weather map
In figure 7, how many millibars is the high pressure reading? Do you think Ireland is experiencing good or bad weather at this time? Why?