With high pressure systems, the weather will tend to become clear or clearing.
You see this effect when air’s invisible water vapor is forced to condense into droplets when it contacts the outside of a cold glass). But droplets won’t form if the glass is only slightly cool . . . thus, rising low pressure air will only produce rain if it gets up where the air is cool enough to condense the water vapor into droplets too heavy to be kept aloft by the rising air. (Clouds are simply water droplets that are small enough to be kept aloft). With very low pressure systems, storms are on the way (if they aren’t there already). Clouds begin to form and move across the sky -thunderhead clouds forming when moist air is thrust very high. Sometimes tornadoes form when very high pressure air collides with very warm, moist low pressure air.
The average air pressure system measures 1013 mb (29. 92 inches of mercury). A typical strong high pressure system measures around 1030 mb (30. 42 inches of mercury). A typical low pressure system measures around 1000 mb (29. 54 inches of mercury.
When the isobars form concentric closed (but not always round) circles, the smallest circle in the center indicates a pressure center. This can be either a high-pressure system (depicted by an “H” in English, “A” in Spanish) or a low pressure system (depicted by an “L” in English, “B” in Spanish). [4] X Research source Air does not flow “down” pressure gradients; it flows “around” them due to the Coriolis effect (Earth spinning). Hence, wind direction is indicated by the isobars, counterclockwise around lows (cyclonic flow) and clockwise around highs (anticyclonic) in the northern hemisphere, thus creating wind. The closer the isobars are to one another, the stronger the winds.
Radar imagery can show low-pressure systems. Tropical cyclones (South Pacific) are also named hurricanes around America or typhoons in coastal Asia.
They are represented on a weather map as isobars with an “H” in the middle isobar and arrows showing which direction the wind is flowing (clockwise in Northern Hemisphere, counterclockwise in the Southern Hemisphere). Like cyclones, they can also be shown with radar imagery.
On a weather map, you will notice some lines that have semi-circles or triangles on either side, or both. These indicate the boundaries for various types of fronts.
A red line with semi-circles on one side represents warm fronts. The side the semi-circles are on represent the direction in which the warm front is heading.
A purple line with semi-circles and triangles both on the same side represents occluded fronts. Whichever side they’re on is the direction the occluded front is going.
Temperature is generally recorded in Celsius degrees and rainfall is recorded in millimeters. In the US, temperatures are in Fahrenheit and rainfall is measured in inches. Cloud cover is indicated by the circle in the middle; the extent to which it is filled indicates the degree to which the sky is overcast.
Isotherms – These are lines on a weather map that connect points through which the isotherm passes have the same temperature. Isotachs – These are lines on a weather map that connect points where the isotach passes have the same wind speed.
