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Name: Roger
Status: student
Grade: other
Location: Outside U.S.
Country: Australia
Date: Summer 2011

What drives extratropical synoptic high and low pressure systems to follow particular paths and for forecasters to be able to forecast that a low will form in a particular location and then move in a particular way? In Australia a typical situation is for a low pressure to form off the east coast. Forecasters may predict it may intensify and move south or dissipate and move east or a number of other scenarios. Mostly their predictions are correct. What indicators are they using for them to use as a basis for their forecasts?


High and low pressure areas in the atmosphere are created by Uneven heating of the earth's surface Forces resulting from the rotation of the earth on its axis Forces exerted by neighboring weather systems.

Uneven heating results in hot patches on earth's surface. The air over the hot patches heats up and rises creating an area of low pressure on the earth's surface. As this hot air rises, it cools. The cooler air will then fall back to the surface creating a high pressure area. But as time passes as the hot air rises, cools and falls back, the rotation of the earth causes the cooler air to fall at a different part of the surface. And as the cooler air falls it experiences forces from the coriolis effect (see: of the rotation of the earth on its axis.

Then, weather data from tracking stations all over the world are assembled into a big picture. This includes local observations by people, automated stations such as buoys at sea and remote land based sites, and earth orbiting satellites. The big meteorological picture is then made available to local weather forecasters who also use local radar to watch rain and snow as it approaches metropolitan areas. This gives people long lead times in preparing for severe weather systems such as hurricanes.

More information is available by going to and searching for "Weather Prediction".

Sincere regards,
Mike Stewart

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