CPL » Meteorology » Weather Maps
20.4 Weather Maps
20.4.2 State the difference between analysis and prognosis charts.
Analysis Chart
An analysis chart shows the actual weather situation at a specified time, based on meteorological observations available at that time.
It may show features such as:
High and low pressure systems
Isobars
Fronts
Troughs and ridges
Other significant weather features
An analysis chart therefore shows what the weather situation was at the stated analysis time.
Prognosis Chart
A prognosis chart, or prognostic chart, shows the forecast weather situation at a specified future time.
It predicts the expected:
Position of highs and lows
Position and movement of fronts
Pressure pattern
Other significant weather features
Key Difference
Analysis chart — shows the weather situation as analysed from actual observations at a specified time.
Prognosis chart — shows the forecast weather situation at a future time.
20.4.4 Describe the general weather feature or conditions associated with each of the following pressure systems:
(a) isobars;
Isobars are lines drawn on a weather chart joining places having the same atmospheric pressure, normally reduced to mean sea level.